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

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.

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

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

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.

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]

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.

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]

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.

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

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

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

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.

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

# A cosmological open quantum system [CL]

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.

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