Tag Archives: Quantum Physics

Does light from steady sources bear any observable imprint of the dispersive intergalactic medium? [IMA]

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http://arxiv.org/abs/1711.11451


There has recently been some interest in the prospect of detecting ionized intergalactic baryons by examining the properties of incoherent light from background cosmological sources, namely quasars. Although the paper by \cite{lieu13} proposed a way forward, it was refuted by the later theoretical work of \cite{hir14} and observational study of \cite{hal16}. In this paper we investigated in detail the manner in which incoherent radiation passes through a dispersive medium both from the frameworks of classical and quantum electrodynamics, which led us to conclude that the premise of \cite{lieu13} would only work if the pulses involved are genuinely classical ones involving many photons per pulse, but unfortunately each photon must not be treated as a pulse that is susceptible to dispersive broadening. We are nevertheless able to change the tone of the paper at this juncture, by pointing out that because current technology allows one to measure the phase of individual modes of radio waves from a distant source, the most reliable way of obtaining irrefutable evidence of dispersion, namely via the detection of its unique signature of a quadratic spectral phase, may well be already accessible. We demonstrate how this technique is only applied to measure the column density of the ionized intergalactic medium.

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R. Lieu and L. Duan
Fri, 1 Dec 17
47/68

Comments: 21 pages, 67 equations, ApJ in press

Quantum chaos of dark matter in the Solar System [CL]

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http://arxiv.org/abs/1711.07815


We perform time-dependent analysis of quantum dynamics of dark matter particles in the Solar System. It is shown that this problem has similarities with a microwave ionization of Rydberg atoms studied previously experimentally and analytically. On this basis it is shown that the quantum effects for chaotic dark matter dynamics become significant for dark matter mass ratio to electron mass being smaller than $2 \times 10^{-15}$. Below this border multiphoton diffusion over Rydberg states of dark matter atom becomes exponentially localized in analogy with the Anderson localization in disordered solids. The life time of dark matter in the Solar System is determined in dependence on mass ratio in the localized phase and a few photon ionization regime. Various implications of these quantum results are discussed for the capture of dark matter from Galaxy and its steady-state density distribution.

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D. Shepelyansky
Thu, 23 Nov 17
48/52

Comments: 5 pages, 2 figures

Quantum chaos of dark matter in the Solar System [CL]

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http://arxiv.org/abs/1711.07815


We perform time-dependent analysis of quantum dynamics of dark matter particles in the Solar System. It is shown that this problem has similarities with a microwave ionization of Rydberg atoms studied previously experimentally and analytically. On this basis it is shown that the quantum effects for chaotic dark matter dynamics become significant for dark matter mass ratio to electron mass being smaller than $2 \times 10^{-15}$. Below this border multiphoton diffusion over Rydberg states of dark matter atom becomes exponentially localized in analogy with the Anderson localization in disordered solids. The life time of dark matter in the Solar System is determined in dependence on mass ratio in the localized phase and a few photon ionization regime. Various implications of these quantum results are discussed for the capture of dark matter from Galaxy and its steady-state density distribution.

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D. Shepelyansky
Thu, 23 Nov 17
25/52

Comments: 5 pages, 2 figures

Quantum to classical transition in the Hořava-Lifshitz quantum cosmology [CL]

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http://arxiv.org/abs/1711.02627


A quasi-Gaussian quantum superposition of Ho\v{r}ava-Lifshitz (HL) stationary states is built in order to describe the transition of the quantum cosmological problem to the related classical dynamics. The obtained HL phase-space superposed Wigner function and its associated Wigner currents describe the conditions for the matching between classical and quantum phase-space trajectories. The matching quantum superposition parameter is associated to the total energy of the classical trajectory which, at the same time, drives the engendered Wigner function to the classical stationary regime. Through the analysis of the Wigner flows, the quantum fluctuations that distort the classical regime can be quantified as a measure of (non)classicality. Finally, the modifications to the Wigner currents due to the inclusion of perturbative potentials are computed in the HL quantum cosmological context. In particular, the inclusion of a cosmological constant provides complementary information that allows for connecting the age of the Universe with the overall stiff matter density profile.

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A. Bernardini, P. Leal and O. Bertolami
Wed, 8 Nov 17
57/84

Comments: 40 pages, 9 figures

Recent progress on the description of relativistic spin: vector model of spinning particle and rotating body with gravimagnetic moment in General Relativity [CL]

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http://arxiv.org/abs/1710.07135


We review the recent results on development of vector models of spin and apply them to study the influence of spin-field interaction on the trajectory and precession of a spinning particle in external gravitational and electromagnetic fields. The formalism is developed starting from the Lagrangian variational problem, which implies both equations of motion and constraints which should be presented in a model of spinning particle. We present a detailed analysis of the resulting theory and show that it has reasonable properties on both classical and quantum level. We describe a number of applications and show how the vector model clarifies some issues presented in theoretical description of a relativistic spin: A) One-particle relativistic quantum mechanics with positive energies and its relation with the Dirac equation and with relativistic {\it Zitterbewegung}; B) Spin-induced non commutativity and the problem of covariant formalism; C) Three-dimensional acceleration consistent with coordinate-independence of the speed of light in general relativity and rainbow geometry seen by spinning particle; D) Paradoxical behavior of the Mathisson-Papapetrou-Tulczyjew-Dixon equations of a rotating body in ultra relativistic limit, and equations with improved behavior.

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A. Deriglazov and W. Ramirez
Mon, 23 Oct 17
52/52

Comments: Invited review article for the Journal “Advances in Mathematical Physics”. Based on the recent works: arXiv:1312.6247, arXiv:1406.6715, arXiv:1409.4756, arXiv:1509.05357, arXiv:1511.00645, arXiv:1609.00043. 61 pages, 3 figures

Matter-wave coherence limit owing to cosmic gravitational wave background [CL]

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http://arxiv.org/abs/1710.05816


We study matter-wave interferometry in the presence of a stochastic background of gravitational waves. It is shown that if the background has a scale-invariant spectrum over a wide bandwidth (which is expected in a class of inflationary models of Big Bang cosmology), then separated-path interference cannot be observed for a lump of matter of size above a limit which is very insensitive to the strength and bandwidth of the fluctuations, unless the interferometer is servo-controlled or otherwise protected. For ordinary solid matter this limit is of order 1–10 mm. A servo-controlled or cross-correlated device would also exhibit limits to the observation of macroscopic interference, which we estimate for ordinary matter moving at speeds small compared to c.

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A. Steane
Tue, 17 Oct 17
44/163

Comments: 8 pages; 3 figures

Searching for axion stars and Q-balls with a terrestrial magnetometer network [CL]

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http://arxiv.org/abs/1710.04323


Light (pseudo-)scalar fields are promising candidates to be the dark matter in the Universe. Under certain initial conditions in the early Universe and/or with certain types of self-interactions, they can form compact dark-matter objects such as axion stars or Q-balls. Direct encounters with such objects can be searched for by using a global network of atomic magnetometers. It is shown that for a range of masses and radii not ruled out by existing observations, the terrestrial encounter rate with axion stars or Q-balls can be sufficiently high (at least once per year) for a detection. Furthermore, it is shown that a global network of atomic magnetometers is sufficiently sensitive to pseudoscalar couplings to atomic spins so that a transit through an ALP star or Q-ball could be detected over a broad range of unexplored parameter space.

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D. Kimball, D. Budker, J. Eby, et. al.
Fri, 13 Oct 17
33/56

Comments: 8 pages, 3 figures

The use of $μ$-Bose gas model for effective modeling of dark matter [CL]

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http://arxiv.org/abs/1709.05931


For the recently introduced $\mu$-deformed analog of Bose gas model ($\mu$-Bose gas model), its thermodynamical aspects e.g. total number of particles and the partition function are certain functions of the parameter $\mu$. This basic $\mu$-dependence of thermodynamics of the $\mu$-Bose gas arises through the so-called $\mu$-calculus, an alternative to the known $q$-calculus (Jackson derivative, etc.), so we include main elements of $\mu$-calculus. Likewise, virial expansion of EOS and virial coefficients, the internal energy, specific heat and the entropy of $\mu$-Bose gas show $\mu$-dependence. Herein, we study thermodynamical geometry of $\mu$-Bose gas model and find the singular behavior of (scalar) curvature, signaling for Bose-like condensation. The critical temperature of condensation $T^{(\mu)}_c$ depending on $\mu$ is given and compared with the usual $T_c$, and with known $T_c^{(p,q)}$ of $p,q$-Bose gas model. Using the results on $\mu$-thermodynamics we argue that the condensate of $\mu$-Bose gas, like the earlier proposed infinite statistics system of particles, can serve for effective modeling of dark matter.

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A. Gavrilik, I. Kachurik, M. Khelashvili, et. al.
Thu, 21 Sep 17
38/50

Comments: 7 pages, two-column style, 2 figures

The Propagation of de Broglie Waves and Its Refraction in Rindler Space- The Possibility of Particle Emission from Classical Black Holes [CL]

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http://arxiv.org/abs/1512.08618


In this article we have studied the propagation of matter waves in Rindler space. We have also developed a formalism to obtained the space dependent refractive index for de Broglie waves associated with a particle and shown the possibility of particle emission from the event horizon of classical black holes, when observed from a uniformly accelerated frame.

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S. Mitra and S. Chakrabarty
Tue, 5 Sep 17
61/76

Comments: 7 pages REVTEX file, no figure

Temporal intensity interferometry: photon bunching on three bright stars [IMA]

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http://arxiv.org/abs/1708.06119


We report the first intensity correlation measured with star light since Hanbury Brown and Twiss’ historical experiments. The photon bunching $g^{(2)}(\tau, r=0)$, obtained in the photon counting regime, was measured for 3 bright stars, $\alpha$ Boo, $\alpha$ CMi, and $\beta$ Gem. The light was collected at the focal plane of a 1~m optical telescope, was transported by a multi-mode optical fiber, split into two avalanche photodiodes and digitally correlated in real-time. For total exposure times of a few hours, we obtained contrast values around $2\times10^{-3}$, in agreement with the expectation for chaotic sources, given the optical and electronic bandwidths of our setup. Comparing our results with the measurement of Hanbury Brown et al. on $\alpha$ CMi, we argue for the timely opportunity to extend our experiments to measuring the spatial correlation function over existing and/or foreseen arrays of optical telescopes diluted over several kilometers. This would enable $\mu$as long-baseline interferometry in the optical, especially in the visible wavelengths with a limiting magnitude of 10.

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W. Guerin, A. Dussaux, M. Fouche, et. al.
Tue, 22 Aug 17
2/51

Comments: Accepted for publication in Mon. Not. Roy. Astron. Soc

Entangled de Sitter from Stringy Axionic Bell pair I: An analysis using Bunch Davies vacuum [CL]

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http://arxiv.org/abs/1708.02265


In this work, we study the quantum entanglement and compute entanglement entropy in de Sitter space for a bipartite quantum field theory driven by axion originating from ${\bf Type~ IIB}$ string compactification on a Calabi Yau three fold (${\bf CY^3}$) and in presence of ${\bf NS5}$ brane. For this compuation, we consider a spherical surface ${\bf S}^2$, which divide the spatial slice of de Sitter (${\bf dS_4}$) into exterior and interior sub regions. We also consider the initial choice of vaccum to be Bunch Davies state. First we derive the solution of the wave function of axion in a hyperbolic open chart by constructing a suitable basis for Bunch Davies vacuum state using Bogoliubov transformation. We then, derive the expression for density matrix by tracing over the exterior region. This allows us to compute entanglement entropy and R$\acute{e}$nyi entropy in $3+1$ dimension. Further we quantify the UV finite contribution of entanglement entropy which contain the physics of long range quantum correlations of our expanding universe. Finally, our analysis compliments the necessary condition for the violation of Bell’s inequality in primordial cosmology due to the non vanishing entanglement entropy for axionic Bell pair.

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S. Choudhury and S. Panda
Wed, 9 Aug 17
32/32

Comments: 68 pages, 9 figures

A cosmological open quantum system [CL]

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http://arxiv.org/abs/1708.00493


We derive the evolution equation for the density matrix of a UV- and IR- limited band of comoving momentum modes of the canonically normalized scalar degree of freedom in two examples of nearly de Sitter universes. Including the effects of a cubic interaction term from the gravitational action and tracing out a set of longer wavelength modes, we find that the evolution of the system is non-Hamiltonian and non-Markovian. We find linear dissipation terms for a few modes with wavelength near the boundary between system and bath and nonlinear dissipation terms for all modes. The non-Hamiltonian terms persist to late times when the scalar field dynamics is such that the curvature perturbation continues to evolve on super-Hubble scales.

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S. Shandera, N. Agarwal and A. Kamal
Thu, 3 Aug 17
47/59

Comments: 5 pages

Decoherence in excited atoms by low-energy scattering [CL]

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http://arxiv.org/abs/1706.03077


We describe a new mechanism of decoherence in excited atoms as a result of thermal particles scattering by the atomic nucleus. It is based on the idea that a single scattering will produce a sudden displacement of the nucleus, which will be perceived by the electron in the atom as an instant shift in the electrostatic potential. This will leave the atom’s wave-function partially projected into lower-energy states which will lead to decoherence of the atomic state. The decoherence is calculated to increase with the excitation of the atom, making observation of the effect easier in Rydberg atoms. We estimate the order of the decoherence for photons and massive particles scattering, analyzing several commonly presented scenarios. Our scheme can be applied to the detection of weakly-interacting particles, like those which may be the constituents of Dark Matter, which interaction was calculated to have a more prominent effect that the background radiation.

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D. Quinones and B. Varcoe
Tue, 13 Jun 17
35/92

Comments: N/A

Fully integrated free-running InGaAs/InP single-photon detector for accurate lidar applications [CL]

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http://arxiv.org/abs/1706.02816


We present a fully integrated InGaAs/InP negative feedback avalanche diode (NFAD) based free-running single-photon detector (SPD) designed for accurate lidar applications. A free-piston Stirling cooler is used to cool down the NFAD with a large temperature range, and an active hold-off circuit implemented in a field programmable gate array is applied to further suppress the afterpulsing contribution. The key parameters of the free-running SPD including photon detection efficiency (PDE), dark count rate (DCR), afterpulse probability, and maximum count rate (MCR) are dedicatedly optimized for lidar application in practice. We then perform a field experiment using a Mie lidar system with 20 kHz pulse repetition frequency to compare the performance between the free-running InGaAs/InP SPD and a commercial superconducting nanowire single-photon detector (SNSPD). Our detector exhibits good performance with 1.6 Mcps MCR (0.6 {\mu}s hold-off time), 10% PDE, 950 cps DCR, and 18% afterpulse probability over 50 {\mu}s period. Such performance is worse than the SNSPD with 60% PDE and 300 cps DCR. However, after performing a specific algorithm that we have developed for afterpulse and count rate corrections, the lidar system performance in terms of range-corrected signal (Pr2) distribution using our SPD agrees very well with the result using the SNSPD, with only a relative error of ~2%. Due to the advantages of low-cost and small size of InGaAs/InP NFADs, such detector provides a practical solution for accurate lidar applications.

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C. Yu, M. Shangguan, H. Xia, et. al.
Mon, 12 Jun 17
20/42

Comments: 10 pages, 7 figures. Accepted for publication in Optics Express

Emergent Dark Energy in Classical Channel Gravity with Matter [CL]

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http://arxiv.org/abs/1706.02312


Motivated by the recent increased interest in energy non-conserving models in cosmology, we extend the analysis of the cosmological consequences of the Classical Channel Model of Gravity (CCG). This model is based on the classical-quantum interaction between a test particle and a metric (classical) and results in a theory with a modified Wheeler-deWitt equation that in turn leads to non conservation of energy. We show that CCG applied to a cosmological scenario with primordial matter leads to an emergent dark fluid that at late times behaves as a curvature term in the Friedmann equations, showing that the late time behaviour is always dominated by the vacuum solutions. We discuss possible observational constraints for this model and that, in its current formulation, CCG eludes any meaningful constraints from current observations.

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R. Pascalie, N. Altamirano and R. Mann
Fri, 9 Jun 17
36/52

Comments: 17 pages, 3 figures, 1 table

Astronomical random numbers for quantum foundations experiments [CL]

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http://arxiv.org/abs/1706.02276


Photons from distant astronomical sources can be used as a classical source of randomness to improve fundamental tests of quantum nonlocality, wave-particle duality, and local realism through Bell’s inequality and delayed-choice quantum eraser tests inspired by Wheeler’s cosmic-scale Mach-Zehnder interferometer gedankenexperiment. Such sources of random numbers may also be useful for information-theoretic applications such as key distribution for quantum cryptography. Here we report on the design and characterization of a device that, with nanosecond latency, outputs a bit based on whether the wavelength of an incoming photon is greater than or less than 700 nm. Using the 1-meter telescope at the Jet Propulsion Laboratory (JPL) Table Mountain Observatory, we recorded the time of arrival of astronomical photons in both color channels from 50 stars of varying color and magnitude, 13 quasars with redshifts up to $z = 3.9$, and the Crab pulsar. For bright quasars, the resulting bitstreams exhibit sufficiently low amounts of mutual information and a sufficiently high ratio of astronomical detections to terrestrial noise to close both the locality and “freedom-of-choice” loopholes when used to set the measurement settings in a test of the Bell-CHSH inequality.

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C. Leung, A. Brown, H. Nguyen, et. al.
Thu, 8 Jun 17
2/69

Comments: 15 pages, 10 figures

Astro-comb calibrator using a turn-key laser frequency comb [IMA]

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http://arxiv.org/abs/1705.07192


Using a turn-key Ti:sapphire femtosecond laser frequency comb and an off-the-shelf supercontinuum device, we report the generation of a 16 GHz frequency comb spanning an 80 nm band about a center wavelength of 570 nm. The light from this turn-key astro-comb is used to calibrate the HARPS-N astrophysical spectrograph for precision radial velocity measurements. The comb-calibrated spectrograph achieves a stability of $\sim$ 1 cm/s within half an hour of averaging time. We also use the turn-key astro-comb to perform calibration of solar spectra obtained with a compact telescope, and to study intrapixel sensitivity variations on the CCD of the spectrograph.

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A. Ravi, D. Phillips, M. Beck, et. al.
Tue, 23 May 17
6/68

Comments: 7 pages, 7 figures, submitted to Optics Express (astrophotonics feature issue)

Quantum decoherence from entanglement during inflation [CL]

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http://arxiv.org/abs/1705.07703


We study the primary entanglement effect on the decoherence of fields reduced density matrix which are in interaction with another fields or independent mode functions. We show that the primary entanglement has a significant role in decoherence of the system quantum state. We find that the existence of entanglement could couple dynamical equations coming from Schr\”{o}dinger equation. We show if one wants to see no effect of the entanglement parameter in decoherence then interaction terms in Hamiltonian can not be independent from each other. Generally, including the primary entanglement destroys the independence of the interaction terms. Our results could be generalized to every scalar quantum field theory with a well defined quantization in a given curved space time.

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A. Rostami and J. Firouzjaee
Tue, 23 May 17
37/68

Comments: 11 pages

Boson star with particle size effects [HEAP]

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http://arxiv.org/abs/1704.06705


A simple model to study boson stars is to consider these stellar objects as quantum systems of $N$ identical self-gravitating particles within a non-relativistic framework. Some results obtained with point-like particles are recalled as well as the validity limits of this model. Approximate analytical calculations are performed using envelope theory for a truncated Coulomb-like potential simulating a particle size. If the boson mass is sufficiently small, the description of small mass boson stars is possible within non-relativistic formalism. The mass and radius of these stellar objects are strongly dependent on the value of the truncation parameter.

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C. Semay
Tue, 25 Apr 17
55/59

Comments: Proceedings of the Workshop in honour of the 65th birthday of Professor Philippe Spindel (UMONS, 2015)

Cosmological Horizons, Uncertainty Principle and Maximum Length Quantum Mechanics [CL]

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http://arxiv.org/abs/1704.05681


The cosmological particle horizon is the maximum measurable length in the Universe. The existence of such a maximum observable length scale implies a modification of the quantum uncertainty principle. Thus due to non-locality of quantum mechanics, the global properties of the Universe could produce a signature on the behaviour of local quantum systems. A Generalized Uncertainty Principle (GUP) that is consistent with the existence of such a maximum observable length scale $l_{max}$ is $\Delta x \Delta p \geq \frac{\hbar}{2}\;\frac{1}{1-\alpha \Delta x^2}$ where $\alpha = l_{max}^{-2}\simeq (H_0/c)^2$ ($H_0$ is the Hubble parameter and $c$ is the speed of light). In addition to the existence of a maximum measurable length $l_{max}=\frac{1}{\sqrt \alpha}$, this form of GUP implies also the existence of a minimum measurable momentum $p_{min}=\frac{3 \sqrt{3}}{4}\hbar \sqrt{\alpha}$. Using appropriate representation of the position and momentum quantum operators we show that the spectrum of the one dimensional harmonic oscillator becomes $\bar{\mathcal{E}}n=2n+1+\lambda_n \bar{\alpha}$ where $\bar{\mathcal{E}}_n\equiv 2E_n/\hbar \omega$ is the dimensionless properly normalized $n^{th}$ energy level, $\bar{\alpha}$ is a dimensionless parameter with $\bar{\alpha}\equiv \alpha \hbar/m \omega$ and $\lambda_n\sim n^2$ for $n\gg 1$ (we show the full form of $\lambda_n$ in the text). For a typical vibrating diatomic molecule and $l{max}=c/H_0$ we find $\bar{\alpha}\sim 10^{-77}$ and therefore for such a system, this effect is beyond reach of current experiments. However, this effect could be more important in the early universe and could produce signatures in the primordial perturbation spectrum induced by quantum fluctuations of the inflaton field.

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L. Perivolaropoulos
Thu, 20 Apr 17
9/49

Comments: 11 pages, 7 Figures. The Mathematica file that was used for the production of the Figures may be downloaded from this http URL

Explaining Recurring Maser Flares in the ISM Through Large-scale Entangled Quantum Mechanical States [GA]

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http://arxiv.org/abs/1704.01491


We apply Dicke’s theory of superradiance introduced in 1954 to the methanol 6.7 GHz and water 22 GHz spectral lines, often detected in molecular clouds as signposts for the early stages of the star formation process. We suggest that superradiance, characterized by burst-like features taking place over a wide range of time-scales, may provide a natural explanation for the recent observations of periodic and seemingly alternating methanol and water maser flares in G107.298+5.639. Although these observations would be very difficult to explain within the context of maser theory, we show that these flares may result from simultaneously initiated 6.7-GHz methanol and 22-GHz water superradiant bursts operating on different time-scales, thus providing a natural mechanism for their observed durations and time ordering. The evidence of superradiance in this source further suggests the existence of entangled quantum mechanical states, involving a very large number of molecules, over distances up to a few kilometres in the interstellar medium.

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F. Rajabi and M. Houde
Thu, 6 Apr 2017
16/43

Comments: 14 pages, 3 figures

Classical Entanglement Structure in the Wavefunction of Inflationary Fluctuations [CL]

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http://arxiv.org/abs/1704.00728


We argue that the preferred classical variables that emerge from a pure quantum state are determined by its entanglement structure in the form of redundant records: information shared between many subsystems. Focusing on the early universe, we ask how classical metric perturbations emerge from vacuum fluctuations in an inflationary background. We show that the squeezing of the quantum state for super-horizon modes, along with minimal gravitational interactions, leads to decoherence and to an exponential number of records of metric fluctuations on very large scales, $\lambda/\lambda_{\rm Hubble}>\Delta_\zeta^{-2/3}$, where $\Delta_\zeta\lesssim 10^{-5}$ is the amplitude of scalar metric fluctuations. This determines a preferred decomposition of the inflationary wavefunction into orthogonal “branches” corresponding to classical metric perturbations, which defines an inflationary entropy production rate and accounts for the emergence of stochastic, inhomogeneous spacetime geometry.

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E. Nelson and C. Riedel
Wed, 5 Apr 17
41/45

Comments: 5 pages, 1 figure. Comments welcome

Doomsdays in a modified theory of gravity: A classical and a quantum approach [CL]

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http://arxiv.org/abs/1703.09263


By far cosmology is one of the most exciting subject to study, even more so with the current bulk of observations we have at hand. These observations might indicate different kinds of doomsdays, if dark energy follows certain patterns. Two of these doomsdays are the Little Rip (LR) and Little Sibling of the Big Rip (LSBR). In this work, aside from proving the unavoidability of the LR and LSBR in the Eddington-inspired-Born-Infeld (EiBI) scenario, we carry out a quantum analysis of the EiBI theory with a matter field, which, from a classical point of view would inevitably lead to a universe that ends with either LR or LSBR. Based on a modified Wheeler-DeWitt equation, we demonstrate that such fatal endings seems to be avoidable.

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I. Albarran, M. Bouhmadi-Lopez, C. Chen, et. al.
Wed, 29 Mar 17
28/63

Comments: 7 pages

Dirac states of an electron in a circular intense magnetic field [HEAP]

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http://arxiv.org/abs/1703.05193


Neutron-star magnetospheres are structured by very intense magnetic fields extending from 100 to 10 5 km traveled by very energetic electrons and positrons with Lorentz factors up to $\sim$ 10 7. In this context, particles are forced to travel almost along the magnetic field with very small gyro-motion, potentially reaching the quantified regime. We describe the state of Dirac particles in a locally uniform, constant and curved magnetic field in the approximation that the Larmor radius is very small compared to the radius of curvature of the magnetic field lines. We obtain a result that admits the usual relativistic Landau states as a limit of null curvature. We will describe the radiation of these states, that we call quantum curvature or synchro-curvature radiation, in an upcoming paper.

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G. Voisin, S. Bonazzola and F. Mottez
Thu, 16 Mar 17
32/92

Comments: N/A

Non-cyclic geometric phases and helicity transitions for neutrino oscillations in magnetic field [CL]

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http://arxiv.org/abs/1703.05027


We show that neutrino spin and spin-flavor transitions involve non-vanishing geometric phases. Analytical expressions are derived for non-cyclic geometric phases arising due to neutrino oscillations in magnetic fields and matter. Several calculations are performed for different cases of rotating and non-rotating magnetic fields in the context of solar neutrinos and neutrinos produced inside neutron stars. It is shown that the neutrino eigenstates carry non-vanishing geometric phases even at large distances from their original point of production. Also the effects of critical magnetic fields and cross boundary effects in case of neutrinos emanating out of neutron stars are analyzed.

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S. Joshi and S. Jain
Thu, 16 Mar 17
87/92

Comments: 12 pages, 7 figures

Cosmic Quantum Optical Probing of Quantum Gravity Through a Gravitational Lens [CL]

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http://arxiv.org/abs/1703.01272


We consider the nonunitary quantum dynamics of neutral massless scalar particles used to model photons around a massive gravitational lens. The gravitational interaction between the lensing mass and asymptotically free particles is described by their second-quantized scattering wavefunctions. Remarkably, the zero-point spacetime fluctuations can induce significant decoherence of the scattered states with spontaneous emission of gravitons, thereby reducing the particles’ coherence as well as energy. This new effect suggests that, when photon polarizations are negligible, such quantum gravity phenomena could lead to measurable anomalous redshift of recently studied astrophysical lasers through a gravitational lens in the range of black holes and galaxy clusters.

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T. Oniga, E. Mansfield and C. Wang
Mon, 6 Mar 17
4/47

Comments: 4 pages, 2 figures

Topological Origin of Geophysical Waves [CL]

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http://arxiv.org/abs/1702.07583


Symmetries and topology are central to an understanding of physics. Topology explains the precise quantization of the Hall effect and the protection of surface states in topological insulators against scattering by non-magnetic impurities or bumps. Subsequent to the discovery of the quantum spin Hall effect, states of matter with different topological properties were classified according to the discrete symmetries of the system. Recently topologically protected edge excitations have been found in artificial lattice structures that support classical waves of various types. The interplay between discrete symmetries and the topology of fluid waves has so far played no role in the study of the dynamics of oceans and atmospheres. Here we show that, as a consequence of the rotation of the Earth that breaks time reversal symmetry, equatorially trapped Kelvin and Yanai waves have a topological origin, manifesting as equatorial edge modes in the rotating shallow water model. These unidirectional edge modes are guaranteed to exist by the non-trivial global structure of the bulk Poincar\’e modes encoded through the first Chern number of value $\pm2$, in agreement with the correspondence between behavior deep in the bulk and edge excitations of a physical system. Thus the oceans and atmospheres of Earth and other rotating planets naturally share fundamental properties with topological insulators, despite the absence of an underlying lattice. As equatorially trapped Kelvin waves are an important component of El Ni\~no Southern Oscillation, and Madden-Julian Oscillation, our results demonstrate the topology plays an unexpected role in Earth’s climate system. These and other geophysical waves of topological origin are protected against static perturbations by time scale separation from other modes that inhibits scattering.

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P. Delplace, J. Marston and A. Venaille
Mon, 27 Feb 17
16/49

Comments: N/A

Quantum Circuit Cosmology: The Expansion of the Universe Since the First Qubit [CL]

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http://arxiv.org/abs/1702.06959


We consider cosmological evolution from the perspective of quantum information. We present a quantum circuit model for the expansion of a comoving region of space, in which initially-unentangled ancilla qubits become entangled as expansion proceeds. We apply this model to the comoving region that now coincides with our Hubble volume, taking the number of entangled degrees of freedom in this region to be proportional to the de Sitter entropy. The quantum circuit model is applicable for at most 140 $e$-folds of inflationary and post-inflationary expansion: we argue that no geometric description was possible before the time $t_1$ when our comoving region was one Planck length across, and contained one pair of entangled degrees of freedom. This approach could provide a framework for modeling the initial state of inflationary perturbations.

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N. Bao, C. Cao, S. Carroll, et. al.
Fri, 24 Feb 17
11/50

Comments: 12 pages, 1 figure. Including appendix

Quantum correlation measurements in interferometric gravitational wave detectors [CL]

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http://arxiv.org/abs/1702.03329


Quantum fluctuations in the phase and amplitude quadratures of light set limitations on the sensitivity of modern optical instruments. The sensitivity of the interferometric gravitational wave detectors, such as the Advanced Laser Interferometer Gravitational wave Observatory (LIGO), is limited by quantum shot noise, quantum radiation pressure noise, and a set of classical noises. We show how the quantum properties of light can be used to distinguish these noises using correlation techniques. Particularly, in the first part of the paper we show estimations of the coating thermal noise and gas phase noise, hidden below the quantum shot noise in the Advanced LIGO sensitivity curve. We also make projections on the observatory sensitivity during the next science runs. In the second part of the paper we discuss the correlation technique that reveals the quantum radiation pressure noise from the background of classical noises and shot noise. We apply this technique to the Advanced LIGO data, collected during the first science run, and experimentally estimate the quantum correlations and quantum radiation pressure noise in the interferometer for the first time.

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D. Martynov, V. Frolov, S. Kandhasamy, et. al.
Tue, 14 Feb 17
29/71

Comments: N/A

Quantum principle of sensing gravitational waves: From the zero-point fluctuations to the cosmological stochastic background of spacetime [CL]

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http://arxiv.org/abs/1702.03905


We carry out a theoretical investigation on the collective dynamics of an ensemble of correlated atoms, subject to both vacuum fluctuations of spacetime and stochastic gravitational waves. A general approach is taken with the derivation of a quantum master equation capable of describing arbitrary confined nonrelativistic matter systems in an open quantum gravitational environment. It enables us to relate the spectral function for gravitational waves and the distribution function for quantum gravitational fluctuations and to indeed introduce a new spectral function for the zero-point fluctuations of spacetime. The formulation is applied to two-level Rydberg-like identical bosonic atoms in a cavity, leading to a gravitational transition mechanism through certain quadrupole moment operators. For a large number $N$ of such atoms, we find their equilibrium state to satisfy the Boltzmann distribution. The overall relaxation rate before reaching equilibrium is found to scale collectively with $N$. However, we are able to identify certain states whose decay and excitation rates with stochastic gravitational waves and vacuum spacetime fluctuations amplify more significantly with a factor of $N^2$. Using such favourable states as a means of measuring both conventional stochastic gravitational waves and novel zero-point spacetime fluctuations, we determine the theoretical lower bounds for the respective spectral functions. Finally, we discuss the implications of our findings on future observations of gravitational waves of a wider spectral window than currently accessible. Especially, the possible sensing of the zero-point fluctuations of spacetime could provide an opportunity to generate initial evidence and further guidance of quantum gravity.

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D. Quinones, T. Oniga, B. Varcoe, et. al.
Tue, 14 Feb 17
51/71

Comments: 13 pages; 4 figures

Mitigating radiation damage of single photon detectors for space applications [CL]

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http://arxiv.org/abs/1702.01186


Single-photon detectors in space must retain useful performance characteristics despite being bombarded with sub-atomic particles. Mitigating the effects of this space radiation is vital to enabling new space applications which require high-fidelity single-photon detection. To this end, we conducted proton radiation tests of various models of avalanche photodiodes (APDs) and one model of photomultiplier tube potentially suitable for satellite-based quantum communications. The samples were irradiated with 106 MeV protons at doses equivalent to lifetimes of 0.6 months, 6 months, 12 months and 24 months in a low-Earth polar orbit. Although most detection properties were preserved, including effciency, timing jitter and afterpulsing probability, all APD samples demonstrated significant increases in dark count rate (DCR) due to radiation-induced damage, many orders of magnitude higher than the 200 counts per second (cps) required for ground-tosatellite quantum communications. We then successfully demonstrated the mitigation of this DCR degradation through the use of deep cooling, to as low as -86 degrees C. This achieved DCR below the required 200 cps over the 24 months orbit duration. DCR was further reduced by thermal annealing at temperatures of +50 to +100 degrees C.

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E. Anisimova, B. Higgins, J. Bourgoin, et. al.
Tue, 7 Feb 17
17/64

Comments: N/A

The Anomalous Magnetic Moment of a photon propagating in a magnetic field [CL]

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http://arxiv.org/abs/1702.00498


We analyze the spectrum of the Hamiltonian of a photon propagating in a strong magnetic field $B\sim B_{\rm{cr}}$, where $B_{\rm cr}= \frac{m^2}{e} \simeq 4.4 \times 10^{13}$ Gauss is the Schwinger critical field . We show that the expected value of the Hamiltonian of a quantized photon for a perpendicular mode is a concave function of the magnetic field $B$. We show by a partially analytic and numerical method that the anomalous magnetic moment of a photon in the one loop approximation is a non – decreasing function of the magnetic field $B$ in the range $0\leq B \leq 30 \, B_{\rm cr}$ We provide a numerical representation of the expression for the anomalous magnetic moment in terms of special functions. We find that the anomalous magnetic moment $\mu_\gamma$ of a photon for $B=30\, B_{\rm cr }$ is $8/3$ of the anomalous magnetic moment of a photon for $B = 1/2 ~ B_{\rm cr}$.

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J. Mielniczuk, D. Lamm, S. Auddy, et. al.
Fri, 3 Feb 17
46/55

Comments: arXiv admin note: text overlap with arXiv:1503.00532 by other authors

Quantum Break-Time of de Sitter [CL]

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http://arxiv.org/abs/1701.08776


The quantum break-time of a system is the time-scale after which its true quantum evolution departs from the classical mean field evolution. For capturing it, a quantum resolution of the classical background – e.g., in terms of a coherent state – is required. In this paper, we first consider a simple scalar model with anharmonic oscillations and derive its quantum break-time. Next, we apply these ideas to de Sitter space. We formulate a simple model of a spin-2 field, which for some time reproduces the de Sitter metric and simultaneously allows for its well-defined representation as quantum coherent state of gravitons. The mean occupation number $N$ of background gravitons turns out to be equal to the de Sitter horizon area in Planck units, while their frequency is given by the de Sitter Hubble parameter. In the semi-classical limit, we show that the model reproduces all the known properties of de Sitter, such as the redshift of probe particles and thermal Gibbons-Hawking radiation, all in the language of quantum $S$-matrix scatterings and decays of coherent state gravitons. Most importantly, this framework allows to capture the $1/N$-effects to which the usual semi-classical treatment is blind. They violate the de Sitter symmetry and lead to a finite quantum break-time of the de Sitter state equal to the de Sitter radius times $N$. We also point out that the quantum-break time is inversely proportional to the number of particle species in the theory. Thus, the quantum break-time imposes the following consistency condition: Older and species-richer universes must have smaller cosmological constants. For the maximal, phenomenologically acceptable number of species, the observed cosmological constant would saturate this bound if our Universe were $10^{100}$ years old in its entire classical history.

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G. Dvali, C. Gomez and S. Zell
Wed, 1 Feb 17
63/67

Comments: 52 pages, 5 figures

Quantum coherence, radiance, and resistance of gravitational systems [CL]

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http://arxiv.org/abs/1701.04122


We develop a general framework for the open dynamics of an ensemble of quantum particles subject to spacetime fluctuations about the flat background. An arbitrary number of interacting bosonic and fermionic particles are considered. A systematic approach to the generation of gravitational waves in the quantum domain is presented that recovers known classical limits in terms of the quadrupole radiation formula and back-reaction dissipation. Classical gravitational emission and absorption relations are quantized into their quantum field theoretical counterparts in terms of the corresponding operators and quantum ensemble averages. Certain arising consistency issues related to factor ordering have been addressed and resolved. Using the theoretical formulation established here with numerical simulations in the quantum regime, we demonstrate new predictions including decoherence through the spontaneous emission of gravitons and collectively amplified “superradiance” of gravitational waves by a highly coherent state of identical particles.

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T. Oniga and C. Wang
Tue, 17 Jan 17
16/81

Comments: 10 pages, 3 figures

Towards Searching for Entangled Photons in the CMB Sky [CL]

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http://arxiv.org/abs/1701.03437


We explore the possibility of detecting an entangled pair of cosmic microwave background (CMB) photons from casually disconnected patches of the sky or other cosmological sources. The measurement uses the standard HBT intensity interferometer with the polarizer orientations for the two detectors chosen as in a Bell inequality experiment. However, unless the angle between the two sources is large such that entanglement is less likely, the entanglement signal is contaminated with un-entangled background which makes it hard to isolate the signal.

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J. Chen, S. Dai, D. Maity, et. al.
Fri, 13 Jan 17
41/44

Comments: 4 pages, 1 figure

Decoherence, discord and the quantum master equation for cosmological perturbations [CL]

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http://arxiv.org/abs/1701.02235


We consider a model for the interaction between the cosmological perturbations and another environmental field during inflation, in order to study decoherence, the quantum to classical transition and the impact on quantum correlations. Given an explicit interaction between the system and environment, we derive a quantum master equation for the reduced density matrix of perturbations, drawing parallels with quantum Brownian motion, where we see the emergence of fluctuation and dissipation terms. Although the master equation is not in Lindblad form, we see how typical solutions exhibit positivity on super-horizon scales, leading to a physically meaningful density matrix. This allows us to write down a Langevin equation with stochastic noise for the classical trajectories which emerge from the quantum system on super-horizon scales. Our master equation reveals many important features characteristic of the quantum to classical transition which are not captured by an isolated pure state. In particular, we find that decoherence grows in strength as modes exit the horizon, and memory effects are negligible, implying that the Langevin description involves white noise. In contrast to pure states, entropy and the spread of the Wigner function increase in time due to environmental interactions, with their evolution determined by the relative strength of squeezing and decoherence. Finally, we use our master equation to quantify the strength of quantum correlations as captured by discord. We show that environmental interactions have a tendency to decrease the size of the discord, but that these corrections are perturbatively small in the coupling. We interpret this in terms of the competing effects of particle creation versus environmental fluctuations, which tend to increase and decrease the discord respectively.

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T. Hollowood and J. McDonald
Tue, 10 Jan 17
30/75

Comments: 22 pages, 12 figures

Bell violation in primordial cosmology [CL]

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http://arxiv.org/abs/1612.09445


In this paper, we have worked on the possibility of setting up an Bell’s inequality violating experiment in the context of primordial cosmology following the fundamental principles of quantum mechanics. To set up this proposal we have introduced a model independent theoretical framework using which we have studied the creation of new massive particles for the scalar fluctuations in the presence of additional time dependent mass parameter. Next we explicitly computed the one point and two point correlation functions from this setup. Then we comment on the measurement techniques of isospin breaking interactions of newly introduced massive particles and its further prospects. After that, we give an example of string theory originated axion monodromy model in this context. Finally, we provide a bound on the heavy particle mass parameter for any arbitrary spin field.

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S. Choudhury, S. Panda and R. Singh
Mon, 2 Jan 17
22/45

Comments: 8 pages, 6 figures, 1 table, Shorter version of arXiv:1607.00237, “Talk presented at Varying Constants and Fundamental Cosmology-VARCOSMOFUN’16. To appear in a special issue of Universe.”. arXiv admin note: text overlap with arXiv:1508.01082 by other authors

On signatures of spontaneous collapse dynamics modified single field inflation [CEA]

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http://arxiv.org/abs/1612.09131


The observed classicality of primordial perturbations, despite their quantum origin during inflation, calls for a mechanism for quantum-to-classical transition of these initial fluctuations. As literature suggests a number of plausible mechanisms which try to address this issue, it is of importance to seek for concrete observational signatures of these several approaches in order to have a better understanding of the early universe dynamics. Among these several approaches, it is the spontaneous collapse dynamics of Quantum Mechanics which is most viable of leaving discrete observational signatures as collapse mechanism inherently changes the generic Quantum dynamics. We observe in this study that the observables from the scalar sector, i.e. scalar tilt $n_s$, running of scalar tilt $\alpha_s$ and running of running of scalar tilt $\beta_s$, can not potentially distinguish a collapse modified inflationary dynamics in the realm of canonical scalar field and $k-$inflationary scenarios. The only distinguishable imprint of collapse mechanism lies in the observables of tensor sector in the form of modified consistency relation and a blue-tilted tensor spectrum only when the collapse parameter $\delta$ is non-zero and positive.

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S. Banerjee, S. Das, K. Kumar, et. al.
Fri, 30 Dec 16
59/64

Comments: 14 pg, 2 tables, 0 figs

Massive Fermi Gas in the Expanding Universe [CEA]

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http://arxiv.org/abs/1612.07249


The behavior of a decoupled ideal Fermi gas in a homogeneously expanding three-dimensional volume is investigated, starting from an equilibrium spectrum. In case the gas is massless and/or completely degenerate, the spectrum of the gas can be described by an effective temperature and/or an effective chemical potential, both of which scale down with the volume expansion. In contrast, the spectrum of a decoupled massive and non-degenerate gas can only be described by an effective temperature if there are strong enough self-interactions such as to maintain an equilibrium distribution. Assuming perpetual equilibration, we study a decoupled gas which is relativistic at decoupling and then is red-shifted until it becomes non-relativistic. We find expressions for the effective temperature and effective chemical potential which allow us to calculate the final spectrum for arbitrary initial conditions. This calculation is enabled by a new expansion of the Fermi-Dirac integral, which is for our purpose superior to the well-known Sommerfeld expansion. We also compute the behavior of the phase space density under expansion and compare it to the case of real temperature and real chemical potential. Using our results for the degenerate case, we also obtain the mean relic velocity of the recently proposed non-thermal cosmic neutrino background.

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A. Trautner
Thu, 22 Dec 16
21/65

Comments: 19 pages, 16 figures

Geometric phases in neutrino oscillations with nonlinear refraction [CL]

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http://arxiv.org/abs/1612.06940


Neutrinos propagating in dense astrophysical environments sustain nonlinear refractive effects due to neutrino-neutrino forward scattering. We study geometric phases in neutrino oscillations that arise out of cyclic evolution of the potential generated by these forward-scattering processes. We perform several calculations, exact and perturbative, that illustrate the robustness of such phases, and of geometric effects more broadly, in the flavor evolution of neutrinos. The scenarios we consider are highly idealized in order to make them analytically tractable, but they suggest the possible presence of complicated geometric effects in realistic astrophysical settings. We also point out that in the limit of extremely high neutrino densities, the nonlinear potential in three flavors naturally gives rise to non-Abelian geometric phases. This paper is intended to be accessible to neutrino experts and non-specialists alike.

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L. Johns and G. Fuller
Thu, 22 Dec 16
33/65

Comments: 17 pages, 3 figures

Physical Effects of the Gravitational $Θ$-Parameter [CL]

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http://arxiv.org/abs/1612.06010


We describe the effect of the gravitational $\Theta$-parameter on the behavior of the stretched horizon of a black hole in $(3+1)$-dimensions. The gravitational $\Theta$-term is a total derivative, however, it affects the transport properties of the horizon. In particular, the horizon acquires a third order parity violating, dimensionless transport coefficient which affects the way localized perturbations scramble on the horizon. In the context of the gauge/gravity duality, the $\Theta$-term induces a non-trivial contact term in the energy-momentum tensor of a $(2+1)-$dimensional large-N gauge theory, which admits a dual gravity description. As a consequence, the dual gauge theory in the presence of the $\Theta$-term acquires the same third order parity violating transport coefficient.

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W. Fischler and S. Kundu
Tue, 20 Dec 16
32/88

Comments: 4 pages. arXiv admin note: substantial text overlap with arXiv:1512.01238

How Decoherence Affects the Probability of Slow-Roll Eternal Inflation [CL]

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http://arxiv.org/abs/1612.04894


Slow-roll inflation can become eternal if the quantum variance of the inflaton field around its slowly rolling classical trajectory is converted into a distribution of classical spacetimes inflating at different rates, and if the variance is large enough compared to the rate of classical rolling that the probability of an increased rate of expansion is sufficiently high. Both of these criteria depend sensitively on whether and how perturbation modes of the inflaton interact and decohere. Decoherence is inevitable as a result of gravitationally-sourced interactions whose strength are proportional to the slow-roll parameters. However, the weakness of these interactions means that decoherence is typically delayed until several Hubble times after modes pass the Hubble scale. We show how to modify the standard picture of eternal inflation to reflect this delayed decoherence. An increased time until decoherence, which gives more time for the quantum variance to grow larger, allows inflation to be eternal at smaller field values than previously realized. Near the maxima of hilltop models, the opposite is true: decoherence happens almost instantaneously before the variance can grow large, making eternal inflation impossible.

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K. Boddy, S. Carroll and J. Pollack
Fri, 16 Dec 16
24/60

Comments: 27 pages, 4 figures

Theoretical foundations of the Schrödinger method for LSS formation [CL]

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http://arxiv.org/abs/1612.04572


It has been shown that the formation of large scale structures (LSS) in the universe can be described in terms of a Schr$\ddot{o}$dinger-Poisson system. This procedure, known as Schr$\ddot{o}$dinger method, has no theoretical basis, but it is intended as a mere tool to model the N-body dynamics of dark matter halos which form LSS. Furthermore, in this approach the “Planck constant” $\hbar$ in the Schr$\ddot{o}$dinger equation is just a free parameter. In this paper we give a theoretical foundation of the Schr$\ddot{o}$dinger method based on the stochastic quantization introduced by Nelson, and on the Calogero conjecture. The order of magnitude of the effective Planck constant is estimated as $\hbar \sim m^{5/3} G^{1/2} (N/<\rho>)^{1/6}$, where $N$ and $m$ are the number and the mass of the dark matter halos, $<\rho_0>$ is their average density, and $G$ the gravitational constant. The relevance of this finding for the study of LSS is discussed.

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F. Briscese
Thu, 15 Dec 16
30/59

Comments: N/A

Time Dependent Rindler Hamiltonian Eigen States in Momentum Space [CL]

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http://arxiv.org/abs/1612.01269


We have developed a formalism to get the time evolution of the eigen states of Rindler Hamiltonian in momentum space. We have shown the difficulties with characteristic curves, and re-cast the time evolution equations in the form of two-dimensional Laplace equation. The solutions are obtain both in polar coordinates as well as in the Cartesian form.

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S. Mitra, S. Das and S. Chakrabarty
Mon, 12 Dec 16
31/61

Comments: Six pages REVTEX file with five .eps figures (included)

A Cosmic Bell Test with Measurement Settings from Astronomical Sources [CL]

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http://arxiv.org/abs/1611.06985


Bell’s theorem states that some predictions of quantum mechanics cannot be reproduced by a local-realist theory. That conflict is expressed by Bell’s inequality, which is usually derived under the assumption that there are no statistical correlations between the choices of measurement settings and anything else that can causally affect the measurement outcomes. In previous experiments, this “freedom of choice” was addressed by ensuring that selection of measurement settings via conventional “quantum random number generators” (QRNGs) was space-like separated from the entangled particle creation. This, however, left open the possibility that an unknown cause affected both the setting choices and measurement outcomes as recently as mere microseconds before each experimental trial. Here we report on a new experimental test of Bell’s inequality that, for the first time, uses distant astronomical sources as “cosmic setting generators.” In our tests with polarization-entangled photons, measurement settings were chosen using real-time observations of Milky Way stars while simultaneously ensuring locality. We observe statistically significant $\gtrsim 11.7 \sigma$ and $\gtrsim 13.8 \sigma$ violations of Bell’s inequality with estimated $p$-values of $ \lesssim 7.4 \times 10^{-32}$ and $\lesssim 1.1 \times 10^{-43}$, respectively, thereby pushing back by $\sim$600 years the most recent time by which any local-realist influences could have engineered the observed Bell violation.

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J. Handsteiner, A. Friedman, D. Rauch, et. al.
Tue, 22 Nov 16
45/79

Comments: 24 pages, 12 figures (including Supplemental Material)

A blueprint for a simultaneous test of quantum mechanics and general relativity in a space-based quantum optics experiment [IMA]

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http://arxiv.org/abs/1611.01327


In this paper we propose an experiment designed to observe a general-relativistic effect on single photon interference. The experiment consists of a folded Mach-Zehnder interferometer, with the arms distributed between a single Earth orbiter and a ground station. By compensating for other degrees of freedom and the motion of the orbiter, this setup aims to detect the influence of general relativistic time dilation on a spatially superposed single photon. The proposal details a payload to measure the required effect, along with an extensive feasibility analysis given current technological capabilities.

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S. Pallister, S. Coop, V. Formichella, et. al.
Mon, 7 Nov 16
7/48

Comments: 21 pages, 9 figures

Schrödinger field theory in curved spacetime: In-In formalism and three-point function for inflationary background [CL]

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http://arxiv.org/abs/1610.05038


We review the Schr\”odinger picture of field theory in curved spacetime and using this formalism, the power spectrum of massive non-interacting, minimally coupled scalars in a fixed de Sitter background is obtained. To calculate the N-point function in Schr\”odinger field theory, the “in-in” formalism is extended in the Friedmann-Lema\^itre-Robertson-Walker (FLRW) universe. We compute the three-point function for primordial scalar field fluctuation in the single field inflation by this in-in formalism. The results are the same as the three-point function in the Heisenberg picture.

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A. Rostami and J. Firouzjaee
Tue, 18 Oct 16
8/70

Comments: 20 pages

Properties of the false vacuum as the quantum unstable state [CL]

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http://arxiv.org/abs/1609.03382


We analyze properties of unstable vacuum states from the point of view of the quantum theory. In the literature one can find some suggestions that some of false (unstable) vacuum states may survive up to times when their survival probability has a non-exponential form. At asymptotically late times the survival probability as a function of time $t$ has an inverse power–like form. We show that at this time region the energy of the false vacuum states tends to the energy of the true vacuum state as $1/t^{2}$ for $t \to \infty$. This means that the energy density in the unstable vacuum state should have analogous properties and hence the cosmological constant $\Lambda = \Lambda (t)$ too. The conclusion is that $\Lambda$ in the Universe with the unstable vacuum should have a form of the sum of the “bare” cosmological constant and of the term of a type $1/t^{2}$: $\Lambda(t) \equiv \Lambda_{bare} + d/ t^{2}$ (where $\Lambda_{bare}$ is the cosmological constant for the Universe with the true vacuum).

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K. Urbanowski
Tue, 4 Oct 16
7/81

Comments: 14 pages, 2 figures, accepted for Theoretical and Mathematical Physics. arXiv admin note: substantial text overlap with arXiv:1304.2796

Constraining symmetron fields with atom interferometry [CEA]

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http://arxiv.org/abs/1609.09275


We apply the new constraints from atom-interferometry searches for screening mechanisms to the symmetron model, finding that these experiments exclude a previously unexplored region of parameter space. We discuss the possibility of networks of domain walls forming in the vacuum chamber, and how this could be used to discriminate between models of screening.

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C. Burrage, A. Kuribayashi-Coleman, J. Stevenson, et. al.
Fri, 30 Sep 16
17/75

Comments: 12 pages, 2 figures

Atomic Interferometry Test of Dark Energy [CEA]

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http://arxiv.org/abs/1609.09242


Atomic interferometry can be used to probe dark energy models coupled to matter. We consider the constraints coming from recent experimental results on models generalising the inverse power law chameleons such as $f(R)$ gravity in the large curvature regime, the environmentally dependent dilaton and symmetrons. Using the tomographic description of these models, we find that only symmetrons with masses smaller than the dark energy scale can be efficiently tested. In this regime, the resulting constraints complement the bounds from the E\”otwash experiment and exclude small values of the symmetron self-coupling.

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P. Brax and A. Davis
Fri, 30 Sep 16
74/75

Comments: 26 pages, 3 figures

Perturbations and quantum relaxation [CL]

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http://arxiv.org/abs/1609.04485


We investigate whether small perturbations can cause relaxation to quantum equilibrium over very long timescales. We consider in particular a two-dimensional harmonic oscillator, which can serve as a model of a field mode on expanding space. We assume an initial wave function with small perturbations to the ground state. We present evidence that the trajectories are highly confined so as to preclude relaxation to equilibrium even over very long timescales. Cosmological implications are briefly discussed.

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A. Kandhadai and A. Valentini
Fri, 16 Sep 16
16/63

Comments: 23 pages, 12 figures

Anomalous spectral lines and relic quantum nonequilibrium [CL]

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http://arxiv.org/abs/1609.04576


We describe general features that might be observed in the line spectra of relic cosmological particles should quantum nonequilibrium be preserved in their statistics. According to our arguments, these features would represent a significant departure from those of a conventional origin. Among other features, we find a possible spectral broadening (for incident photons) that is proportional to the energy resolution of the recording telescope (and so could be orders of magnitude larger than any intrinsic broadening). Notably, for a range of possible initial conditions we find the possibility of spectral line `narrowing’ whereby a telescope could observe a spectral line which is narrower than it should conventionally be able to resolve. We briefly discuss implications for the indirect search for dark matter.

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N. Underwood and A. Valentini
Fri, 16 Sep 16
21/63

Comments: 15 pages, 5 figures

Decoherence as a way to measure extremely soft collisions with Dark Matter [CL]

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http://arxiv.org/abs/1609.04145


A new frontier in the search for dark matter (DM) is based on the idea of detecting the decoherence caused by DM scattering against a mesoscopic superposition of normal matter. Such superpositions are uniquely sensitive to very small momentum transfers from new particles and forces, especially DM with a mass below 100 MeV. Here we investigate what sorts of dark sectors are inaccessible with existing methods but would induce noticeable decoherence in the next generation of matter interferometers. We show that very soft, but medium range (0.1 nm – 1 {\mu}m) elastic interactions between matter and DM are particularly suitable. We construct toy models for such interactions, discuss existing constraints, and delineate the expected sensitivity of forthcoming experiments. The first hints of DM in these devices would appear as small variations in the anomalous decoherence rate with a period of one sidereal day. This is a generic signature of interstellar sources of decoherence, clearly distinguishing it from terrestrial backgrounds. The OTIMA experiment under development in Vienna will begin to probe Earth-thermalizing DM once sidereal variations in the background decoherence rate are pushed below one part in a hundred for superposed 5-nm gold nanoparticles. The proposals by Bateman et al. and Geraci et al. could be similarly sensitive, although they would require at least a month of data taking. DM that is absorbed or elastically reflected by the Earth, and so avoids a greenhouse density enhancement, would not be detectable by those three experiment. On the other hand, aggressive proposals of the MAQRO collaboration and Pino et al. would immediately open up many orders of magnitude in DM mass, interaction range, and coupling strength, regardless of how DM behaves in bulk matter.

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C. Riedel and I. Yavin
Thu, 15 Sep 16
21/56

Comments: 13 pages main text, 5 figures, 13 pages of appendices and references

Quantum and Classical Behavior in Interacting Bosonic Systems [CL]

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http://arxiv.org/abs/1609.01342


It is understood that in free bosonic theories, the classical field theory accurately describes the full quantum theory when the occupancy numbers of systems are very large. However, the situation is less understood in interacting theories, especially on time scales longer than the dynamical relaxation time. Recently there have been claims that the quantum theory deviates spectacularly from the classical theory on this time scale, even if the occupancy numbers are extremely large. Furthermore, it is claimed that the quantum theory quickly thermalizes while the classical theory does not. The evidence for these claims comes from noticing a spectacular difference in the time evolution of expectation values of quantum operators compared to the classical micro-state evolution. If true, this would have dramatic consequences for many important phenomena, including laboratory studies of interacting BECs, dark matter axions, preheating after inflation, etc. In this work we critically examine these claims. We show that in fact the classical theory can describe the quantum behavior in the high occupancy regime, even when interactions are large. The connection is that the expectation values of quantum operators in a single quantum micro-state are approximated by the corresponding classical ensemble average over many classical micro-states. Furthermore, by the ergodic theorem, the classical ensemble average of local fields with statistical translation invariance is the spatial average of a single micro-state. So the correlation functions of the quantum and classical field theories of a single micro-state approximately agree at high occupancy, even in interacting systems. Furthermore, both quantum and classical field theories can thermalize, when appropriate coarse graining is introduced, with the classical case requiring a cutoff on low occupancy UV modes. We discuss applications of our results.

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M. Hertzberg
Wed, 7 Sep 16
31/61

Comments: 7 pages, 4 plots

Entanglement Growth after a Global Quench in Free Scalar Field Theory [CL]

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http://arxiv.org/abs/1609.00872


We compute the entanglement and R\’enyi entropy growth after a global quench in various dimensions in free scalar field theory. We study two types of quenches: a boundary state quench and a global mass quench. Both of these quenches are investigated for a strip geometry in 1, 2, and 3 spatial dimensions, and for a spherical geometry in 2 and 3 spatial dimensions. We compare the numerical results for massless free scalars in these geometries with the predictions of the analytical quasiparticle model based on EPR pairs, and find excellent agreement in the limit of large region sizes. At subleading order in the region size, we observe an anomalous logarithmic growth of entanglement coming from the zero mode of the scalar.

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J. Cotler, M. Hertzberg, M. Mezei, et. al.
Tue, 6 Sep 16
68/74

Comments: 32 pages, 9 figures

Is the quilted multiverse consistent with a thermodynamic arrow of time? [CL]

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http://arxiv.org/abs/1608.08798


Theoretical achievements, as well as much controversy surround multiverse theory. Various types of multiverses, with an increasing amount of complexity, were suggested and thoroughly discussed by now. While these types are very different, they all share the same basic idea – our physical reality consists of more than just one universe. Each universe within a possibly huge multiverse might be slightly or even very different from the others. The quilted multiverse is one of these types, whose uniqueness arises from the postulate that every possible event will occur infinitely many times in infinitely many universes. In this paper we show that the quilted multiverse is not self-consistent due to the instability of entropy decrease under small perturbations. We therefore propose a modified version of the quilted multiverse which might overcome this shortcoming. It includes only those universes where the minimal entropy occurs at the same instant of (cosmological) time.

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Y. Aharonov, E. Cohen and T. Shushi
Thu, 1 Sep 16
68/74

Comments: 11 pages, 1 figure. Comments are welcome

Cosmic Decoherence: Massive Fields [CL]

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http://arxiv.org/abs/1608.07909


We study the decoherence of massive fields during inflation based on the Zurek’s density matrix approach. With the cubic interaction between inflaton and massive fields, the reduced density matrix for the massive fields can be calculated in the Schr\”odinger picture which is related to the variance of the non-Gaussian exponent in the wave functional. The decoherence rate is computed in the one-loop form from functional integration. For heavy fields with $m\gtrsim \mathcal{O}(H)$, quantum fluctuations will easily stay in the quantum state and decoherence is unlikely. While for light fields with mass smaller than $\mathcal{O}(H)$, quantum fluctuations are easily decohered within $5\sim10$ e-folds after Hubble crossing. Thus heavy fields can play a key role in studying problems involving inflationary quantum information.

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J. Liu, C. Sou and Y. Wang
Tue, 30 Aug 16
15/78

Comments: 26 pages, 3 figures

Glauber theory and the quantum coherence of curvature inhomogeneities [CL]

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http://arxiv.org/abs/1608.05843


The curvature inhomogeneities are systematically scrutinized in the framework of the Glauber approach. The amplified quantum fluctuations of the scalar and tensor modes of the geometry are shown to be first-order coherent while the interference of the corresponding intensities is larger than in the case of Bose-Einstein correlations. After showing that the degree of second-order coherence does not suffice to characterize unambiguously the curvature inhomogeneities, we argue that direct analyses of the degrees of third and fourth-order coherence are necessary to discriminate between different correlated states and to infer more reliably the statistical properties of the large-scale fluctuations. We speculate that the moments of the multiplicity distributions of the relic phonons might be observationally accessible thanks to new generations of instruments able to count the single photons of the Cosmic Microwave Background in the THz region.

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M. Giovannini
Tue, 23 Aug 16
34/51

Comments: 35 pages

Characterization of very narrow spectral lines with temporal intensity interferometry [IMA]

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http://arxiv.org/abs/1607.05897


Context: Some stellar objects exhibit very narrow spectral lines in the visible range additional to their blackbody radiation. Natural lasing has been suggested as a mechanism to explain narrow lines in Wolf-Rayet stars. However, the spectral resolution of conventional astronomical spectrographs is still about two orders of magnitude too low to test this hypothesis. Aims: We want to resolve the linewidth of narrow spectral emissions in starlight. Methods: A combination of spectral filtering with single-photon-level temporal correlation measurements breaks the resolution limit of wavelength-dispersing spectrographs by moving the linewidth measurement into the time domain. Results: We demonstrate in a laboratory experiment that temporal intensity interferometry can determine a 20 MHz wide linewidth of Doppler-broadened laser light, and identify a coherent laser light contribution in a blackbody radiation background.

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P. Tan and C. Kurtsiefer
Thu, 21 Jul 16
12/48

Comments: 4 pages, 4 figures

Magneto-optic effects of the Cosmic Microwave Background [CEA]

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http://arxiv.org/abs/1607.02094


Generation of magneto-optic effects by the cosmic microwave background (CMB) in the presence of cosmic magnetic fields is studied. Four mechanisms which generate polarization of the CMB such as the Cotton-Mouton effect, the vacuum polarization in external magnetic field, the photon-pseudoscalar mixing in external magnetic field and the Faraday effect are studied. Considering the CMB linearly polarized at decoupling time due to Thomson scattering, it is shown that second order effects in the magnetic field amplitude such as the Cotton-Mouton effect in plasma and the vacuum polarization (Euler-Heisenberg term) in cosmic magnetic field, would generate elliptic polarization of the CMB at post decoupling time depending on the photon frequency and magnetic field strength. The Cotton-Mouton effect in plasma turns out to be the dominant effect in the generation of CMB elliptic polarization in the low frequency part while the vacuum polarization in magnetic field is the dominant process in the high frequency part. The effect of pseudoscalar particles (axions and axion-like particles) on the CMB polarization is also studied. It is shown that photon-pseudoscalar particle mixing in cosmic magnetic field generates elliptic polarization of the CMB as well, depending on the circumstances and even in the case of initially unpolarized CMB. New limits on the pseudoscalar parameter space are set. Prior decoupling CMB polarization due to pseudoscalar particles is also discussed.

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D. Ejlli
Fri, 8 Jul 16
5/56

Comments: 45 pages, 2 figures

Quantum Walks as simulators of neutrino oscillations in vacuum and matter [CL]

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http://arxiv.org/abs/1607.00529


We analyze the simulation of Dirac neutrino oscillations using quantum walks, both in vacuum and in matter. We show that this simulation, in the continuum limit, reproduces a set of coupled Dirac equations that describe neutrino flavor oscillations, and we make use of this to establish a connection with neutrino phenomenology, thus allowing to fix the parameters of the simulation for a given neutrino experiment. We also analyze how matter effects for neutrino propagation can be simulated in the quantum walk. In this way, important features, such as the MSW effect, can be incorporated. Thus, the simulation of neutrino oscillations with the help of quantum walks might be useful to explore these effects in extreme conditions, such as the solar interior or supernovae, in a complementary way to existing experiments.

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G. Molfetta and A. Perez
Tue, 5 Jul 16
72/80

Comments: 3 figures, 6 pages

Bell violation in the Sky [CL]

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http://arxiv.org/abs/1607.00237


In this work, we have studied the possibility of setting up Bell’s inequality violating experiment in the context of cosmology, based on the basic principles of quantum mechanics. First we start with the physical motivation of implementing the Bell’s inequality violation in the context of cosmology. Then to set up the cosmological Bell violating test experiment we introduce a model independent theoretical framework using which we have studied the creation of new massive particles by implementing the WKB approximation method for the scalar fluctuations in presence of additional time dependent mass contribution. Next using the background scalar fluctuation in presence of new time dependent mass contribution, we explicitly compute the expression for the one point and two point correlation functions. Furthermore, using the results for one point function we introduce a new theoretical cosmological parameter which can be expressed in terms of the other known inflationary observables and can also be treated as a future theoretical probe to break the degeneracy amongst various models of inflation. Additionally, we also fix the scale of inflation in a model independent way without any prior knowledge of primordial gravitational waves. Next, we also comment on the technicalities of measurements from isospin breaking interactions and the future prospects of newly introduced massive particles in cosmological Bell violating test experiment. Further, we cite a precise example of this set up applicable in the context of string theory motivated axion monodromy model. Then we comment on the explicit role of decoherence effect and high spin on cosmological Bell violating test experiment. In fine, we provide a theoretical bound on the heavy particle mass parameter for scalar fields, graviton and other high spin fields from our proposed setup.

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S. Choudhury, S. Panda and R. Singh
Mon, 4 Jul 16
56/58

Comments: 202 pages, 16 figures, 1 table

Hot dense magnetized ultrarelativistic spinor matter in a slab [CL]

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http://arxiv.org/abs/1606.08241


Properties of hot dense ultrarelativistic spinor matter in a slab of finite width, placed in a transverse uniform magnetic field, are studied. The admissible set of boundary conditions is determined by the requirement that spinor matter be confined inside the slab. In thermal equilibrium, the chiral separation effect in the slab is shown to depend both on temperature and chemical potential; this is distinct from the unrealistic case of the magnetic field filling the unbounded (infinite) medium, when the effect is temperature-independent. In the realistic case of the slab, a stepwise behaviour of the axial current density at zero temperature is smoothed out as temperature increases, turning into a linear behaviour at infinitely large temperature. A choice of boundary conditions can facilitate either augmentation or attenuation of the chiral separation effect; in particular, the effect can persist even at zero chemical potential, if temperature is nonzero. Thus the boundary condition can serve as a source that is additional to the spinor matter density.

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Y. Sitenko
Tue, 28 Jun 16
32/58

Comments: 27 pages, 5 figures. arXiv admin note: text overlap with arXiv:1603.09268

Exact Solution for Chameleon Field, Self-Coupled Through the Ratra-Peebles Potential with n = 1 and Confined Between Two Parallel Plates [CL]

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http://arxiv.org/abs/1606.06867


We calculate the chameleon field profile, confined between two parallel plates, in the chameleon field theory with Ratra-Peebles self-interaction potential with index n = 1. We give the exact analytical solution in terms of Jacobian elliptic functions, depending on the mass density of the ambient matter. The obtained analytical solution can be used in qBounce experiments, measuring transition frequencies between quantum gravitational states of ultracold neutrons and also for the calculation of the chameleon field induced Casimir force for the CANNEX experiment. We show that the chameleon-matter interactions with coupling constants beta < 10^4 can be probed by qBounce experiments with sensitivities Delta E < 10^(-18)eV.

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A. Ivanov, G. Cronenberg, R. Hollwieser, et. al.
Thu, 23 Jun 16
15/49

Comments: 1 figure, 6 pages

Detecting continuous gravitational waves with superfluid $^4$He [CL]

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http://arxiv.org/abs/1606.04980


Direct detection of gravitational waves is opening a new window onto our universe. Here, we study the sensitivity to continuous-wave strain fields of a kg-scale optomechanical system formed by the acoustic motion of superfluid helium-4 parametrically coupled to a superconducting microwave cavity. This narrowband detection scheme can operate at very high $Q$-factors, while the resonant frequency is tunable through pressurization of the helium in the 0.1-1.5 kHz range. The detector can therefore be tuned to a variety of astrophysical sources and can remain sensitive to a particular source over a long period of time. For reasonable experimental parameters, we find that strain fields on the order of $h\sim 10^{-23} /\sqrt{\rm Hz}$ are detectable. We show that the proposed system can significantly improve the limits on gravitational wave strain from nearby pulsars within a few months of integration time.

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S. Singh, L. Lorenzo, I. Pikovski, et. al.
Fri, 17 Jun 16
65/65

Comments: N/A

Gravitational wave detection with optical lattice atomic clocks [CL]

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http://arxiv.org/abs/1606.01859


We propose a space-based gravitational wave detector consisting of two spatially separated, drag-free satellites sharing ultra-stable optical laser light over a single baseline. Each satellite contains an optical lattice atomic clock, which serves as a sensitive, narrowband detector of the local frequency of the shared laser light. A synchronized two-clock comparison between the satellites will be sensitive to the effective Doppler shifts induced by incident gravitational waves (GWs) at a level competitive with other proposed space-based GW detectors, while providing complementary features. The detected signal is a differential frequency shift of the shared laser light due to the relative velocity of the satellites, rather than a phase shift arising from the relative satellite positions, and the detection window can be tuned through the control sequence applied to the atoms’ internal states. This scheme enables the detection of GWs from continuous, spectrally narrow sources, such as compact binary inspirals, with frequencies ranging from ~3 mHz – 10 Hz without loss of sensitivity, thereby bridging the detection gap between space-based and terrestrial GW detectors. Our proposed GW detector employs just two satellites, is compatible with integration with an optical interferometric detector, and requires only realistic improvements to existing ground-based clock and laser technologies.

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S. Kolkowitz, I. Pikovski, N. Langellier, et. al.
Tue, 7 Jun 16
52/80

Comments: 8 pages, 2 figures, and supplemental material

Bell's Inequalities for Continuous-Variable Systems in Generic Squeezed States [CL]

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http://arxiv.org/abs/1605.02944


Bell’s inequality for continuous-variable bipartite systems is studied. The inequality is expressed in terms of pseudo-spin operators and quantum expectation values are calculated for generic two-mode squeezed states characterized by a squeezing parameter $r$ and a squeezing angle $\varphi$. Allowing for generic values of the squeezing angle is especially relevant when $\varphi$ is not under experimental control, such as in cosmic inflation, where small quantum fluctuations in the early Universe are responsible for structures formation. Compared to previous studies restricted to $\varphi=0$ and to a fixed orientation of the pseudo-spin operators, allowing for $\varphi\neq 0$ and optimizing the angular configuration leads to a completely new and rich phenomenology. Two dual schemes of approximation are designed that allow for comprehensive exploration of the squeezing parameters space. In particular, it is found that Bell’s inequality can be violated when the squeezing parameter $r$ is large enough, $r\gtrsim 1.12$, and the squeezing angle $\varphi$ is small enough, $\varphi\lesssim 0.34\,e^{-r}$.

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J. Martin and V. Vennin
Thu, 12 May 16
54/59

Comments: 9 pages without appendices (38 pages total), 16 figures, to be published in Physical Review A

Classical and quantum cosmology of the little rip abrupt event [CL]

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http://arxiv.org/abs/1604.08365


We analyze from a classical and quantum point of view the behavior of the universe close to a little rip, which can be interpreted as a big rip sent towards the infinite future. Like a big rip singularity, a little rip implies the destruction of all bounded structure in the Universe and is thus an event where quantum effects could be important. We present here a new phantom scalar field model for the little rip. The quantum analysis is performed in quantum geometrodynamics, with the Wheeler-DeWitt equation as its central equation. We find that the little rip can be avoided in the sense of the DeWitt criterion, that is, by having a vanishing wave function at the place of the little rip. Therefore our analysis completes the answer to the question: can quantum cosmology smoothen or avoid the divergent behavior genuinely caused by phantom matter? We show that this can indeed happen for the little rip, similar to the avoidance of a big rip and a little sibling of the big rip.

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I. Albarran, M. Bouhmadi-Lopez, C. Kiefer, et. al.
Fri, 29 Apr 16
38/57

Comments: 14 pages, 3 figures, RevTex4-1

Photon Bubble Turbulence in Cold Atomic Gases [CL]

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http://arxiv.org/abs/1604.08114


Turbulent radiation flow is ubiquitous in many physical systems where light-matter interaction becomes relevant. Photon bubbling, in particular, has been identified as the main source of turbulent radiation transport in many astrophysical objects, such as stars and accretion disks. This mechanism takes place when radiation trapping in optically dense media becomes unstable, leading to the energy dissipation from the larger to the smaller bubbles. Here, we report on the observation of photon bubble turbulence in cold atomic gases in the presence of multiple scattering of light. The instability is theoretically explained by a fluid description for the atom density coupled to a diffusive transport equation for the photons, which is known to be accurate in the multiple scattering regime investigated here. We determine the power spectrum of the atom density fluctuations, which displays an unusual $\sim k^{-4}$ scaling, and entails a complex underlying turbulent dynamics resulting from the formation of dynamical bubble-like structures. We derive a power spectrum from the theoretical photon bubble model which, to a high level of accuracy, explains the observations. The experimental results reported here, along with the theoretical model we developed may shed light on the analogue photon bubble instabilities in astrophysical scenarios.

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J. Rodrigues, J. Rodrigues, A. Ferreira, et. al.
Thu, 28 Apr 16
57/57

Comments: 5 pages

Dark energy from non-unitarity in quantum theory [CL]

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http://arxiv.org/abs/1604.04183


We consider a scheme whereby it is possible to reconcile semi-classical Einstein’s equation with the violation of the conservation of the expectation value of energy-momentum that is associated with dynamical reduction theories of the quantum state for matter. The very interesting out-shot of the formulation is the appearance of a nontrivial contribution to an effective cosmological constant (which is not strictly constant). This opens the possibility of using models for dynamical collapse of the wave function to compute its value. Another interesting implication of our analysis is that tiny violations of energy-momentum conservation with negligible local effects can become very important on cosmological scales at late times.

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T. Josset, A. Perez and D. Sudarsky
Fri, 15 Apr 16
28/51

Comments: 8 pages, 2 figures

One Bubble to Rule Them All [CL]

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http://arxiv.org/abs/1604.03580


We apply the principles of quantum mechanics and quantum cosmology to predict probabilities for our local observations of a universe undergoing false vacuum eternal inflation. At a sufficiently fine-grained level, histories of the universe describe a mosaic of bubble universes separated by inflationary regions. We show that predictions for local observations can be obtained directly from sets of much coarser grained histories which only follow a single bubble. These coarse-grained histories contain neither information about our unobservable location nor about the unobservable large-scale structure outside our own bubble. Applied to a landscape of false vacua in the no-boundary state we predict our local universe emerged from the dominant decay channel of the lowest energy false vacuum. We compare and contrast this framework for prediction based on quantum cosmology with traditional approaches to the measure problem in cosmology.

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J. Hartle and T. Hertog
Thu, 14 Apr 16
26/53

Comments: 33 pages, 5 figures, revtex

Control of a velocity-sensitive audio-band quantum non-demolition interferometer [CL]

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http://arxiv.org/abs/1603.07756


The Sagnac speed meter interferometer topology can potentially provide enhanced sensitivity to gravitational waves in the audio-band compared to equivalent Michelson interferometers. A challenge with the Sagnac speed meter interferometer arises from the intrinsic lack of sensitivity at low frequencies where the velocity-proportional signal is smaller than the noise associated with the sensing of the signal. Using as an example the on-going proof-of-concept Sagnac speed meter experiment in Glasgow, we quantify the problem and present a solution involving the extraction of a small displacement-proportional signal. This displacement signal can be combined with the existing velocity signal to enhance low frequency sensitivity, and we derive optimal filters to accomplish this for different signal strengths. We show that the extraction of the displacement signal for low frequency control purposes can be performed without reducing significantly the quantum non-demolition character of this type of interferometer.

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S. Leavey, S. Danilishin, A. Glafke, et. al.
Mon, 28 Mar 16
7/40

Comments: N/A

Limits of time in cosmology [CL]

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http://arxiv.org/abs/1603.05449


We provide a discussion of some main ideas in our project about the physical foundation of the time concept in cosmology. It is standard to point to the Planck scale (located at $\sim 10^{-43}$ seconds after a fictitious “Big Bang” point) as a limit for how far back we may extrapolate the standard cosmological model. In our work we have suggested that there are several other (physically motivated) interesting limits — located at least thirty orders of magnitude before the Planck time — where the physical basis of the cosmological model and its time concept is progressively weakened. Some of these limits are connected to phase transitions in the early universe which gradually undermine the notion of ‘standard clocks’ widely employed in cosmology. Such considerations lead to a ‘scale problem’ for time which becomes particularly acute above the electroweak phase transition (before $\sim 10^{-11}$ seconds). Other limits are due to problems of building up a cosmological reference frame, or even contemplating a sensible notion of proper time, if the early universe constituents become too quantum. This ‘quantum problem’ for time arises e.g. if a pure quantum phase is contemplated at the beginning of inflation at, say, $\sim 10^{-34}$ seconds.

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S. Rugh and H. Zinkernagel
Fri, 18 Mar 16
1/53

Comments: 20 pages, 1 figure. To appear in “The Philosophy of Cosmology”; edited by K. Chamcham, J. Silk, J. Barrow and S. Saunders. Cambridge University Press, 2016

Quantum clock: A critical discussion on spacetime [CL]

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http://arxiv.org/abs/1603.03723


We critically discuss the measure of very short time intervals. By means of a Gedankenexperiment, we describe an ideal clock based on the occurrence of completely random events. Many previous thought experiments have suggested fundamental Planck-scale limits on measurements of distance and time. Here we present a new type of thought experiment, based on a different type of clock, that provide further support for the existence of such limits. We show that the minimum time interval $\Delta t$ that this clock can measure scales as the inverse of its size $\Delta r$. This implies an uncertainty relation between space and time: $\Delta r$ $\Delta t$ $> G \hbar / c^4$; where G, $\hbar$ and c are the gravitational constant, the reduced Planck constant, and the speed of light, respectively. We outline and briefly discuss the implications of this uncertainty conjecture.

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L. Burderi, T. Salvo and R. Iaria
Mon, 14 Mar 16
26/47

Comments: 10 pages, published in Physical Review D

Inflation and the Measurement Problem [CL]

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http://arxiv.org/abs/1602.01216


We discuss the cosmological measurement problem (see [1] for a review), and propose a solution. Our approach is an effective wavefunction collapse mechanism arising from a novel interaction between Fourier modes, to be contrasted with fundamental modifications to the Schrodinger equation [2, 3].

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S. Alexander, D. Jyoti and J. Magueijo
Thu, 4 Feb 16
9/50

Comments: 4 pages, 2 figures

Quantum Decoherence During Inflation from Gravitational Nonlinearities [CL]

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http://arxiv.org/abs/1601.03734


We study the inflationary quantum-to-classical transition for the adiabatic curvature perturbation $\zeta$ due to quantum decoherence, focusing on the role played by squeezed-limit mode couplings. We evolve the quantum state $\Psi$ in the Schr\”odinger picture, for a generic cubic coupling to additional environment degrees of freedom. Focusing on the case of minimal gravitational interactions, we find the evolution of the reduced density matrix for a given long-wavelength fluctuation by tracing out the other (mostly shorterwavelength) modes of $\zeta$ as an environment. We show that inflation produces phase oscillations in the wave functional $\Psi[\zeta(\mathbf{x})]$, which suppress off-diagonal components of the reduced density matrix, leaving a diagonal mixture of different classical configurations. Gravitational nonlinearities thus provide a minimal mechanism for generating classical stochastic perturbations from inflation. We identify the time when decoherence occurs, which is delayed after horizon crossing due to the weak coupling, and find that Hubble-scale modes act as the decohering environment. We also comment on the observational relevance of decoherence and its relation to the squeezing of the quantum state.

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E. Nelson
Mon, 18 Jan 16
41/50

Comments: 32 pages, 10 figures. Comments welcome

Dicke's Superradiance in Astrophysics. I — The 21 cm Line [GA]

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http://arxiv.org/abs/1601.01717


We have applied the concept of superradiance introduced by Dicke in 1954 to the ISM by extending the corresponding analysis to the magnetic dipole interaction characterizing the atomic hydrogen 21 cm line. Although it is unlikely that superradiance could take place in thermally relaxed regions, in situations where the conditions necessary for superradiance are met (i.e., close atomic spacing, high velocity coherence, population inversion, and long dephasing time-scales compared to those related to coherent behavior), our results suggest that relatively low levels of population inversion over short astronomical length-scales (e.g., as compared to those required for maser amplification) can lead to the cooperative behavior required for superradiance in the ISM. Given the results of our analysis, we expect the observational properties of superradiance to be characterized by the emission of high intensity, spatially compact, burst-like features potentially taking place over short periods ranging from minutes to days.

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F. Rajabi and M. Houde
Mon, 11 Jan 16
2/57

Comments: 38 pages, 7 figures, submitted to the ApJ

Dicke's Superradiance in Astrophysics. II — The OH 1612 MHz Line [SSA]

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http://arxiv.org/abs/1601.01718


We apply the concept of superradiance introduced by Dicke in 1954 to the OH molecule 1612 MHz spectral line often used for the detection of masers in circumstellar envelopes of evolved stars. As the detection of 1612 MHz OH masers in the outer shells of envelopes of these stars implies the existence of a population inversion and a high level of velocity coherence, and that these are two necessary requirements for superradiance, we investigate whether superradiance can also happen in these regions. Superradiance is characterized by high intensity, spatially compact, burst-like features taking place over time-scales on the order of seconds to years, depending on the size and physical conditions present in the regions harboring such sources of radiation. Our analysis suggests that superradiance provides a valid explanation for previous observations of intensity flares detected in that spectral line for the U Orionis Mira star and the IRAS18276-1431 pre-planetary nebula.

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F. Rajabi and M. Houde
Mon, 11 Jan 16
42/57

Comments: 18 pages, 4 figures, submitted to the ApJ

Quantum Gravitational Force Between Polarizable Objects [CL]

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http://arxiv.org/abs/1512.07632


Since general relativity is a consistent low energy effective field theory, it is possible to compute quantum corrections to classical forces. Here we compute a quantum correction to the gravitational potential between a pair of polarizable objects. We study two distant bodies and compute a quantum force from their induced quadrupole moments due to two graviton exchange. The effect is in close analogy to the Casimir-Polder and London-van der Waals forces between a pair of atoms from their induced dipole moments due to two photon exchange. The new effect is computed from the shift in vacuum energy of metric fluctuations due to the polarizability of the objects. We compute the potential energy at arbitrary distances compared to the wavelengths in the system, including the far and near regimes. In the far distance, or retarded, regime, the potential energy takes on a particularly simple form: $V(r)=-3987\,\hbar\,c\,G^2\alpha_{1S}\,\alpha_{2S}/(4\,\pi\,r^{11})$, where $\alpha_{1S},\,\alpha_{2S}$ are the static gravitational quadrupole polarizabilities of each object. We provide estimates of this effect.

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L. Ford, M. Hertzberg and J. Karouby
Fri, 25 Dec 15
14/28

Comments: 5 pages, 1 figure, in double column format

Axion Dark Matter Coupling to Resonant Photons via Magnetic Field [CL]

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http://arxiv.org/abs/1512.05547


We show that the magnetic component of the photon field produced by dark matter axions via the two-photon coupling mechanism in a Sikivie Haloscope is an important parameter passed over in previous analysis and experiments. The interaction of the produced photons will be resonantly enhanced as long as they couple to the electric or magnetic mode structure of the Haloscope cavity. For typical Haloscope experiments the electric and magnetic coupling is the same and implicitly assumed in past sensitivity calculations. However, for future planned searches such as those at high frequency, which synchronize multiple cavities, the sensitivity will be altered due to different magnetic and electric couplings. We discuss the implications of the full electromagnetic form factor and propose new experiments using lumped 3D LC resonators (or re-entrant cavities) with separated electric and magnetic fields to probe currently unbounded regions of the axion mass parameter space.

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B. McAllister, S. Parker and M. Tobar
Thu, 24 Dec 15
12/28

Comments: 5 pages, 4 figures. Version 2: Corrected typographical errors

Membrane Paradigm, Gravitational $Θ$-Term and Gauge/Gravity Duality [CL]

Posted on by

http://arxiv.org/abs/1512.01238


Following the membrane paradigm, we explore the effect of the gravitational $\Theta$-term on the behavior of the stretched horizon of a black hole in (3+1)-dimensions. We reformulate the membrane paradigm from a quantum path-integral point of view where we interpret the macroscopic properties of the horizon as effects of integrating out the region inside the horizon. The gravitational $\Theta$-term is a total derivative, however, using our framework we show that this term affects the transport properties of the horizon. In particular, the horizon acquires a third order parity violating, dimensionless transport coefficient which affects the way localized perturbations scramble on the horizon. Then we consider a large-N gauge theory in (2+1)-dimensions which is dual to an asymptotically AdS background in (3+1)-dimensional spacetime to show that the $\Theta$-term induces a non-trivial contact term in the energy-momentum tensor of the dual theory. As a consequence, the dual gauge theory in the presence of the $\Theta$-term acquires the same third order parity violating transport coefficient.

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W. Fischler and S. Kundu
Mon, 7 Dec 15
1/46

Comments: 28+8 pages

Quantum entanglement from the holographic principle [CL]

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http://arxiv.org/abs/1109.3542


It is suggested that quantum entanglement emerges from the holographic principle stating that all of the information of a region (bulk bits) can be described by the bits on its boundary surface. There are redundancy and information loss in the bulk bits that lead to the nonlocal correlation among the bulk bits. Quantum field theory overestimates the independent degrees of freedom in the bulk. The maximum entanglement in the universe increases as the size of the cosmic horizon and this could be related with the arrow of time and dark energy.

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J. Lee
Thu, 29 Oct 15
36/67

Comments: 3 page, 1 figure

Quantum Discord of Cosmic Inflation: Can we Show that CMB Anisotropies are of Quantum-Mechanical Origin? [CEA]

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http://arxiv.org/abs/1510.04038


We investigate the quantumness of primordial cosmological fluctuations and its detectability. The quantum discord of inflationary perturbations is calculated for an arbitrary splitting of the system, and shown to be very large on super-Hubble scales. This entails the presence of large quantum correlations, due to the entangled production of particles with opposite momentums during inflation. To determine how this is reflected at the observational level, we study whether quantum correlators can be reproduced by a non-discordant state, i.e. a state with vanishing discord that contains classical correlations only. We demonstrate that this can be done for the power spectrum, the price to pay being twofold: first, large errors in other two-point correlation functions, that cannot however be detected since hidden in the decaying mode; second, the presence of intrinsic non-Gaussianity the detectability of which remains to be determined but which could possibly rule out a non-discordant description of the Cosmic Microwave Background. If one abandons the idea that perturbations should be modeled by Quantum Mechanics and wants to use a classical stochastic formalism instead, we show that any two-point correlators on super-Hubble scales can exactly be reproduced regardless of the squeezing of the system. The later becomes important only for higher order correlation functions, that can be accurately reproduced only in the strong squeezing regime.

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J. Martin and V. Vennin
Thu, 15 Oct 15
24/57

Comments: 15 pages plus appendices (total 31 pages), 3 figures, 1 table

Robust predictions for the large-scale cosmological power deficit from primordial quantum nonequilibrium [CL]

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http://arxiv.org/abs/1510.03508


The de Broglie-Bohm pilot-wave formulation of quantum theory allows the existence of physical states that violate the Born probability rule. Recent work has shown that in pilot-wave field theory on expanding space relaxation to the Born rule is suppressed for long-wavelength field modes, resulting in a large-scale power deficit {\xi}(k) which for a radiation-dominated expansion is found to have a characteristic (approximate) inverse-tangent dependence on k. In this paper we show that the functional form of {\xi}(k) is robust under changes in the initial nonequilibrium distribution as well as under the addition of an inflationary era at the end of the radiation-dominated phase. In both cases the predicted deficit {\xi}(k) remains an inverse-tangent function of k. Furthermore, with the inflationary phase the dependence of the fitting parameters on the number of superposed pre-inflationary energy states is comparable to that found previously. Our results indicate that an inverse-tangent power deficit is likely to be a fairly general and robust signature of quantum relaxation in the early universe.

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S. Colin and A. Valentini
Wed, 14 Oct 15
64/66

Comments: 20 pages, 9 figures

Statistical anisotropy and cosmological quantum relaxation [CEA]

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http://arxiv.org/abs/1510.02523


We show that cosmological quantum relaxation predicts an anisotropic primordial power spectrum with a specific dependence on wavenumber k. We explore some of the consequences for precision measurements of the cosmic microwave background (CMB). Quantum relaxation is a feature of the de Broglie-Bohm pilot-wave formulation of quantum theory, which allows the existence of more general physical states that violate the Born probability rule. Recent work has shown that relaxation to the Born rule is suppressed for long-wavelength field modes on expanding space, resulting in a large-scale power deficit with a characteristic inverse-tangent dependence on k. Because the quantum relaxation dynamics is independent of the direction of the wave vector for the relaxing field mode, in the limit of weak anisotropy we are able to derive an expression for the anisotropic power spectrum that is determined by the power deficit function. As a result, the off-diagonal terms in the CMB covariance matrix are also determined by the power deficit. We show that the lowest-order l-(l+1) inter-multipole correlations have a characteristic scaling with multipole moment l. Our derived spectrum also predicts a residual statistical anisotropy at small scales, with an approximate consistency relation between the scaling of the l-(l+1) correlations and the scaling of the angular power spectrum at high l. We also predict a relationship between the l-(l+1) correlations at large and small scales. Cosmological quantum relaxation appears to provide a single physical mechanism that predicts both a large-scale power deficit and a range of statistical anisotropies, together with potentially testable relationships between them.

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A. Valentini
Mon, 12 Oct 15
42/55

Comments: 42 pages, 4 figures

Quantum coherent oscillations in the early universe [CEA]

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http://arxiv.org/abs/1509.08895


Cosmic inflation is commonly assumed to be driven by quantum fields. Quantum mechanics predicts phenomena such as quantum fluctuations and tunneling of the field. Here we show an example of a quantum interference effect which goes beyond the semi-classical treatment and which may be of relevance in the early universe. We study the quantum coherent dynamics for a tilted, periodic potential, which results in genuine quantum oscillations of the inflaton field, analogous to Bloch oscillations in condensed matter and atomic systems. Our results show that quantum interference phenomena may be of relevance in cosmology.

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I. Pikovski and A. Loeb
Wed, 30 Sep 15
67/71

Comments: 4 pages, 2 figures

Exotic Rotational Correlations in Emergent Quantum Geometry [CL]

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http://arxiv.org/abs/1509.07997


Estimates are presented of exotic, purely rotational correlations that arise in large systems if directions in space-time emerge from Planck scale quantum elements with no fixed classical background space. In the time domain, directions to world lines at finite separation $R$ from any world line coherently fluctuate in the classical (that is, $R\rightarrow \infty$) inertial frame, on a timescale $R/c$, by an angle of order $R^{-1/2}$ in Planck units. The exact exotic correlation function is computed for the signal in a Sagnac type interferometer of arbitrary shape. The signal variance is equal to twice the enclosed area divided by the perimeter, in Planck units. It is conjectured that exotic Planck scale rotational correlations, entangled with the strong interactions, determine the value of the cosmological constant. Cosmic acceleration may be viewed heuristically as centrifugal acceleration by rotational fluctuations of the matter vacuum. An experiment concept is sketched, based on a reconfiguration of the Fermilab Holometer.

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C. Hogan
Tue, 29 Sep 15
32/69

Comments: 25 pages, 6 figures

An FPGA-based Instrumentation Platform for use at Deep Cryogenic Temperatures [CL]

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http://arxiv.org/abs/1509.06809


We describe the operation of a cryogenic instrumentation platform incorporating commercially- available field-programmable gate arrays (FPGAs). The functionality of the FPGAs at temperatures approaching 4 kelvin enables signal routing, multiplexing, and complex digital signal processing in close proximity to cooled devices or detectors within the cryostat. The performance of the FPGAs in a cryogenic environment is evaluated, including clock speed, error rates, and power consumption. Although constructed for the purpose of controlling and reading out quantum computing devices with low latency, the instrument is generic enough to be of broad use in a range of cryogenic applications.

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I. Lamb, J. Colless, J. Hornibrook, et. al.
Thu, 24 Sep 15
15/60

Comments: N/A

Non-Relativistic Approximation of Dirac Equation for Slow Fermions Coupled to the Chameleon and Torsion Fields in the Gravitational Field of the Earth [CL]

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http://arxiv.org/abs/1509.04014


We analyse a non-relativistic approximation of the Dirac equation for slow fermions, coupled to the chameleon field and torsion in the spacetime with the Schwarzschild metric, taken in the weak gravitational field of the Earth approximation. We follow the analysis of the Dirac equation in the curved spacetime with torsion, proposed by Kostelecky (Phys. Rev. D69, 105009 (2004)), and apply the Foldy–Wouthuysen transformations. We derive the effective low-energy gravitational potentials for slow fermions, coupled to the gravitational field of the Earth, the chameleon field and to torsion with minimal and non-minimal couplings.

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A. Ivanov and M. Wellenzohn
Tue, 15 Sep 15
60/83

Comments: 12 pages

Comparative description of the evolving universe in classical and quantum geometrodynamics [CL]

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http://arxiv.org/abs/1509.02740


The description of the universe evolving in time according to general relativity is given in comparison with the quantum description of the same universe in terms of quasiclassical wave functions. The spacetime geometry is determined by the Robertson-Walker metric. It is shown that the main equation of the quantum geometrodynamics is reduced to the non-linear Hamilton-Jacobi equation. Its non-linearity is caused by a new source of the gravitational field, which has a purely quantum dynamical nature, and is additional to ordinary matter sources. In quasiclassical approximation, the non-linear equation of motion is linearized and reduces to the Friedmann equation with the additional quantum source of gravity (or anti-gravity) in the form of the stiff Zel’dovich matter. The semi-classical wave functions of the universe, in which different types of matter-energies dominate, are obtained. As examples, the cases of the domination of radiation, barotropic fluid, or new quantum matter-energy are discussed. The probability of the transition from the quantum state, where radiation dominates into the state, in which barotropic fluid in the form of dust is dominant, is calculated. In the era of matter-radiation equality, this probability has the same order of magnitude as the matter density contrast.

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V. Kuzmichev and V. Kuzmichev
Thu, 10 Sep 15
43/67

Comments: 16 pages

State of the art for ab initio vs empirical potentials for predicting 6e$^{-}$ excited state molecular energies: Application to Li$_{2}\left(b,1^{3}Π_{u}\right)$ [CL]

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http://arxiv.org/abs/1508.07184


We build the first analytic empirical potential for the most deeply bound $\mbox{Li}_{2}$ state: $b\left(1^{3}\Pi_{u}\right)$. Our potential is based on experimental energy transitions covering $v=0-34$, and very high precision theoretical long-range constants. It provides high accuracy predictions up to $v=100$ which pave the way for high-precision long-range measurements, and hopefully an eventual resolution of the age old discrepancy between experiment and theory for the $\mbox{Li}\left(2^{2}S\right)+\mbox{Li}\left(2^{2}P\right)$ $C_{3}$ value. State of the art ab initio calculations predict vibrational energy spacings that are all in at most 0.8 cm$^{-1}$ disagreement with the empirical potential.

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N. Dattani and R. Roy
Mon, 31 Aug 15
28/63

Comments: Feedback encouraged. 16 pages, 3 figures

Probing the noncommutative structure of space with a quantum harmonic oscillator driven by gravitational wave [CL]

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http://arxiv.org/abs/1508.02876


We investigate the quantum mechanical transitions, induced by the combined effect of Gravitational wave (GW) and noncommutative (NC) structure of space, among the states of a 2-dimensional harmonic oscillator. The phonon modes excited by the passing GW within the resonant bar-detector are formally identical to forced harmonic oscillator and they represent a length variation of roughly the same order of magnitude as the characteristic length-scale of spatial noncommutativity estimated from the phenomenological upper bound of the NC parameter. This motivates our present work. We employ a number of different GW wave-forms that are typically expected from possible astronomical sources. We find that the transition probablities are quite sensitive to the nature of polarization of the GW. We further elaborate on the particular type of sources of GW radiation which can induce transitions that can be used as effective probe of the spatial noncommutative structure.

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A. Saha and S. Gangopadhyay
Thu, 13 Aug 15
39/49

Comments: 6 pages, RevTex, No figures

A model with cosmological Bell inequalities [CL]

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http://arxiv.org/abs/1508.01082


We discuss the possibility of devising cosmological observables which violate Bell’s inequalities. Such observables could be used to argue that cosmic scale features were produced by quantum mechanical effects in the very early universe. As a proof of principle, we propose a somewhat elaborate inflationary model where a Bell inequality violating observable can be constructed.

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J. Maldacena
Thu, 6 Aug 15
17/48

Comments: 18+6 pages, 10 figures

Performance of a radiatively cooled system for quantum optomechanical experiments in space [CL]

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http://arxiv.org/abs/1508.01032


The performance of a radiatively cooled instrument is investigated in the context of optomechanical quantum experiments, where the environment of a macroscopic particle in a quantum-superposition has to be cooled to less than 20\,K in deep space. A heat-transfer analysis between the components of the instrument as well as a transfer-function analysis on thermal oscillations induced by the spacecraft interior and by dissipative sources is performed. The thermal behaviour of the instrument in an orbit around a Lagrangian point and in a highly elliptical Earth orbit is discussed. Finally, we investigate further possible design improvements aiming at lower temperatures of the environment of the macroscopic particle. These include a mirror-based design of the imaging system on the optical bench and the extension of the heat shields.

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A. Pilan-Zanoni, J. Burkhardt, U. Johann, et. al.
Thu, 6 Aug 15
36/48

Comments: 13 pages, 11 figures, 3 tables

Dynamical interpretation of the wavefunction of the universe [CL]

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http://arxiv.org/abs/1507.06727


In this paper, we study the physical meaning of the wavefunction of the universe. With the continuity equation derived from the Wheeler-DeWitt (WDW) equation in the minisuperspace model, we show that the quantity $\rho(a)=|\psi(a)|^2$ for the universe is inversely proportional to the Hubble parameter of the universe. Thus, $\rho(a)$ represents the probability density of the universe staying in the state $a$ during its evolution, which we call the dynamical interpretation of the wavefunction of the universe. We demonstrate that the dynamical interpretation can predict the evolution laws of the universe in the classical limit as those given by the Friedmann equation. Furthermore, we show that the value of the operator ordering factor $p$ in the WDW equation can be determined to be $p=-2$.

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D. He, D. Gao and Q. Cai
Mon, 27 Jul 15
40/40

Comments: N/A

Exponentiating Higgs [CL]

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http://arxiv.org/abs/1506.05761


The scalar models with exponential interaction, introduced in arXiv:1506.00987, include theories with $\langle \phi(x)\rangle\neq0$. Here, we first consider the theory obtained by normal ordering the exponential of the integrated potential $\int d^Dx\mu^D \exp(-\alpha\phi)$, rather than of $V(\phi)$ itself. This corresponds to fill-in the vacuum of the free scalar theory coupled to the external source with the scalar modes. Next, we show that such a regularization prescription, that we are able to implement in the path-integral formulation, also cures some classical potentials which may be unbounded below. We focus on $V(\phi)=m^4\big(e^{-\phi/m}-e^{\phi/m}\big)$, whose regularized partition function $$ W_R[J]={}_J\langle 0| :e^{-\int d^4xV(\phi)}:|0\rangle_J $$ leads to the exact result $$ \langle\phi(x)\rangle=2m \ , $$ in agreement with the experimental data. Another test is that, while the $(2N+1)$-point function is non-trivial, the full propagator is the free one, so that $m^2$ also corresponds to the pole of the propagator. Such an investigation suggests a natural way to get the lagrangian of the Standard Model, with a different Higgs lagrangian, that may be tested in future experiments at LHC.

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M. Matone
Wed, 24 Jun 15
20/54

Comments: 9 pages. Relevant additions. Typos corrected

Electromagnetic Casimir effect for conducting plates in de Sitter spacetime [CL]

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http://arxiv.org/abs/1505.07353


Two-point functions, the mean field squared and the vacuum expectation value (VEV) of the energy-momentum tensor are investigated for the electromagnetic field in the geometry of parallel plates on background of $(D+1)$% -dimensional dS spacetime. We assume that the field is prepared in the Bunch-Davies vacuum state and on the plates a boundary condition is imposed that is a generalization of the perfectly conducting boundary condition for an arbitrary number of spatial dimensions. It is shown that for $D\geq 4$ the background gravitational field essentially changes the behavior of the VEVs at separations between the plates larger than the curvature radius of dS spacetime. At large separations, the Casimir forces are proportional to the inverse fourth power of the distance for all values of spatial dimension $D\geq 3$. For $D\geq 4$ this behavior is in sharp contrast with the case of plates in Minkowski bulk where the force decays as the inverse $(D+1)$th power of the distance.

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A. Kotanjyan, A. Saharian and H. Nersisyan
Thu, 28 May 15
49/53

Comments: 14 pages, 1 figure

Schrödinger Equation of a particle in an Uniformly Accelerated Frame and the Possibility of a New kind of Quanta [CL]

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http://arxiv.org/abs/1505.05495


In this article we have developed a formalism to obtain the Schr$\ddot{\rm{o}}$dinger equation for a particle in a frame undergoing an uniform acceleration in an otherwise flat Minkowski space-time geometry. We have presented an exact solution of the equation and obtained the eigenfunctions and the corresponding eigenvalues. It has been observed that the Schr$\ddot{\rm{o}}$dinger equation can be reduced to an one dimensional hydrogen atom problem. Whereas, the quantized energy levels are exactly identical with that of an one dimensional quantum harmonic oscillator. Hence considering transitions, we have predicted the existence of a new kind of quanta, which will either be emitted or absorbed if the particles get excited or de-excited respectively.

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S. De and S. Chakrabarty
Mon, 25 May 15
17/47

Comments: 4 pages REVTEX file, no figure

A 3+1 formalism for quantum electrodynamical corrections to Maxwell equations in general relativity [HEAP]

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http://arxiv.org/abs/1505.05847


Magnetized neutron stars constitute a special class of compact objects harbouring gravitational fields that deviate strongly from the Newtonian weak field limit. Moreover strong electromagnetic fields anchored into the star give rise to non-linear corrections to Maxwell equations described by quantum electrodynamics (QED). Electromagnetic fields close to or above the critical value of $\BQ=4.4\times10^9$~T are probably present in some pulsars and for most of the magnetars. To account properly for emission emanating from the neutron star surface like for instance thermal radiation and its polarization properties, it is important to include general relativistic (GR) effects simultaneously with non-linear electrodynamics. This can be achieved through a 3+1 formalism known in general relativity and that incorporates QED perturbations to Maxwell equations. Starting from the lowest order corrections to the Lagrangian for the electromagnetic field, as given for instance by Born-Infeld or Euler-Heisenberg theory, we derive the non-linear Maxwell equations in general relativity including quantum vacuum effects. We also derive a prescription for the force-free limit and show that these equations can be solved with classical finite volume methods for hyperbolic conservation laws. It is therefore straightforward to include general relativity and quantum electrodynamics in the description of neutron star magnetospheres by using standard classical numerical techniques borrowed from Maxwell and Newton theory. As an application, we show that spin-down luminosity corrections associated to QED effects are negligible with respect to GR corrections.

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J. Petri
Fri, 22 May 15
9/67

Comments: Accepted for publication in Monthly Notices of the Royal Astronomical Society Main Journal

Why Boltzmann Brains Don't Fluctuate Into Existence From the De Sitter Vacuum [CL]

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http://arxiv.org/abs/1505.02780


Many modern cosmological scenarios feature large volumes of spacetime in a de Sitter vacuum phase. Such models are said to be faced with a “Boltzmann Brain problem” – the overwhelming majority of observers with fixed local conditions are random fluctuations in the de Sitter vacuum, rather than arising via thermodynamically sensible evolution from a low-entropy past. We argue that this worry can be straightforwardly avoided in the Many-Worlds (Everett) approach to quantum mechanics, as long as the underlying Hilbert space is infinite-dimensional. In that case, de Sitter settles into a truly stationary quantum vacuum state. While there would be a nonzero probability for observing Boltzmann-Brain-like fluctuations in such a state, “observation” refers to a specific kind of dynamical process that does not occur in the vacuum (which is, after all, time-independent). Observers are necessarily out-of-equilibrium physical systems, which are absent in the vacuum. Hence, the fact that projection operators corresponding to states with observers in them do not annihilate the vacuum does not imply that such observers actually come into existence. The Boltzmann Brain problem is therefore much less generic than has been supposed.

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K. Boddy, S. Carroll and J. Pollack
Thu, 14 May 15
2/57

Comments: Based on a talk given by SMC at, and to appear in the proceedings of, the Philosophy of Cosmology conference in Tenerife, September 2014