Tag Archives: General Physics

Interacting cosmic strings and Dark matter-For the case of missing stars [CL]

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http://arxiv.org/abs/2303.11955


This work discusses a few theories including the interaction of dark matter, cosmic strings, and locally coupled dark energy. The paper also examines mathematical models used to describe the pressure and density within a star, including the polytropic relationship and the Lane-Emden equation. Simulation results from the IllustrisTNG datasets are also presented, providing insights into the interacting dark matter solutions. With the derived solutions this paper, it explores the possible causes for the sudden disappearance of the star PHL293B-LBV

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N. Shriethar and N. Rajendran
Wed, 22 Mar 23
47/68

Comments: 23 pages, 2 figures

The CGF dark matter fluid [CL]

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http://arxiv.org/abs/2211.02881


The cosmological gauge field (CGF) is a classical solution of SU(2)-weak gauge theory oscillating rapidly in time. It is the dark matter driving the CGF cosmology. A general, local, mathematically natural construction of the CGF is given here. The macroscopic properties are derived. The CGF is an irrotational perfect fluid. It provides a synchronized global time coordinate and a global rest frame. There is a conserved number density. The energy density and pressure are related by the same equation of state as derived in the CGF cosmology and used in the TOV stellar structure equations for stars made of CGF dark matter. The present construction justifies the TOV solution. Some possible routes towards testing the theory are suggested at the end.

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D. Friedan
Tue, 8 Nov 22
20/79

Comments: 15 pages. Details of calculations are in a note in the ancillary files

Generalized Interacting Dark Energy Model and Loop Quantum Cosmology [CL]

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http://arxiv.org/abs/2205.15751


The recently observed accelerated expansion of the universe has put a challenge for its theoretical understanding. As a possible explanation of this, it is considered that the most part of the present universe is filled with a form of energy that exerts a negative pressure called dark energy, which drives the acceleration. In the present work, we assume a dynamical dark energy model, where dark energy interacts with matter and grows at the expense of the latter. Using this model, we discuss the evolution of the universe within the context of loop quantum cosmology. Our work successfully explains the presently observed accelerated expansion of the universe, by predicting that the present universe is phantom dominated. We also found that in the past, the expansion of the universe was decelerated one and transition from deceleration to acceleration would occur at $t_{q=0}=0.688t_0$, where $t_0$ is the present age of the universe. Again, our analysis predicted that at the transition time, the universe would be dominated with quintessence type dark energy.

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S. Swain, D. Sahu, D. Dwivedee, et. al.
Wed, 1 Jun 22
27/65

Comments: Accepted for publication in Astrophysics and Space Science Journal having the manuscript number ASTR-D-21-00429R2

The Electroweak Horizon Problem [CL]

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http://arxiv.org/abs/2205.14046


Spontaneously broken symmetries in particle physics may have produced several phase transitions in cosmology, e.g., at the GUT energy scale (~10^15 GeV), resulting in a quasi-de Sitter inflationary expansion, solving the background temperature horizon problem. This transition would have occurred at t~10^-36 to 10^-33 seconds, leading to a separation of the strong and electroweak forces. The discovery of the Higgs boson confirms that the Universe must have undergone another phase transition at the electroweak (EWPT) scale 159.5+/-1.5 GeV, about 10^-11 seconds later, when fermions and the W^+/- and Z^0 bosons gained mass, leading to the separation of the electric and weak forces. But today the vacuum expectation value (vev) of the Higgs field appears to be uniform throughout the visible Universe, a region much larger than causally-connected volumes at the EWPT. The discovery of the Higgs boson thus creates another serious horizon problem for LCDM, for which there is currently no established theoretical resolution. The EWPT was a smooth crossover, however, so previously disconnected electroweak vacuua might have homogenized as they gradually came into causal contact. But using the known Higgs potential and vev, we estimate that this process would have taken longer than the age of the Universe, so it probably could not have mitigated the emergence of different standard model parameters across the sky. The EWPT horizon problem thus argues against the expansion history of the early Universe predicted by standard cosmology.

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F. Melia
Mon, 30 May 22
9/47

Comments: 15 pages. Accepted for publication in Physics of the Dark Universe

There is no electroweak horizon problem [CL]

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http://arxiv.org/abs/2205.14045


Contrary to a recent assertion [Fulvio Melia “The electroweak horizon problem” 2022], there is no electroweak horizon problem.

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J. Cline
Mon, 30 May 22
19/47

Comments: 1 page; accepted for Physics of the Dark Universe

Evolution of Primordial Dark Matter Planets in the Early Universe [CL]

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http://arxiv.org/abs/2205.13386


In a recent paper we had discussed possibility of DM at high redshifts forming primordial planets composed entirely of DM to be one of the reasons for not detecting DM (as the flux of ambient DM particles would be consequently reduced). In this paper we discuss the evolution of these DM objects as the Universe expands. As Universe expands there will be accretion of DM, helium and hydrogen layers (discussed in detail) on these objects. As they accumulate more and more mass, the layers get heated up leading to nuclear reactions which burn H and He when a critical thickness is reached. In the case of heavier masses of these DM objects, matter can be ejected explosively. It is found that the time scale of ejection is smaller than those from other compact objects like neutron stars (that lead to x-ray bursts). These flashes of energy could be a possible observational signature for these dense DM objects.

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K. V, K. Arun and C. Sivaram
Fri, 27 May 22
35/61

Comments: 14 pages, 6 tables, 2 figures, 24 equations

Can the Blackett conjecture directly account for the magnetic fields of celestial bodies and galaxies? And, is a lab-based test for the Blackett conjecture feasible? [CL]

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http://arxiv.org/abs/2010.02734


According to the Blackett conjecture, any neutral rotating body acquires a magnetic moment proportional to its angular momentum. Using the data on the dipolar magnetic field of Mars, we put a stringent upper limit on the value of the Blackett’s constant, the dimensionless constant that relates the magnetic moment to the angular momentum. As a consequence, the Blackett effect cannot directly account for the magnetic fields of celestial bodies and galaxies. We also show that the Blackett effect cannot be tested in a laboratory since the magnetic moment of any rotating lab-scale object would be much smaller than the one produced by the well-known Barnett effect.

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L. Campanelli
Wed, 7 Oct 20
72/76

Comments: 3 pages, no figures

Introduction: Detectability of Future Earth [CL]

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http://arxiv.org/abs/1902.08035


Earth’s future detectability depends upon the trajectory of our civilization over the coming centuries. Human civilization is also the only known example of an energy-intensive civilization, so our history and future trajectories provide the basis for thinking about how to find life elsewhere. This special issue of Futures features contributions that consider the future evolution of the Earth system from an astrobiological perspective, with the goal of exploring the extent to which anthropogenic influence could be detectable across interstellar distances. This collection emphasizes the connection between the unfolding future of the Anthropocene with the search for extraterrestrial civilizations. Our rate of energy consumption will characterize the extent to which our energy-intensive society exerts direct influence on climate, which in turn may limit the ultimate lifetime of our civilization. If the answer to Fermi’s question is that we are alone, so that our civilization represents the only form of intelligent life in the galaxy (or even the universe), then our responsibility to survive is even greater. If we do find evidence of another civilization on a distant exoplanet, then at least we will know that our trajectory can be managed. But as long as our searches turn up empty, we must stay vigilant to keep our future secure.

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J. Haqq-Misra
Fri, 22 Feb 19
23/52

Comments: Introduction to the special issue on the Detectability of Future Earth, published in Futures (volume 106, pages 1-44)

A Unifying Theory of Dark Energy and Dark Matter: Negative Masses and Matter Creation within a Modified $Λ$CDM Framework [CL]

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http://arxiv.org/abs/1712.07962


Dark energy and dark matter constitute 95% of the observable Universe. Yet the physical nature of these two phenomena remains a mystery. Einstein suggested a long-forgotten solution: gravitationally repulsive negative masses, which drive cosmic expansion and cannot coalesce into light-emitting structures. However, contemporary cosmological results are derived upon the reasonable assumption that the Universe only contains positive masses. By reconsidering this assumption, I have constructed a toy model which suggests that both dark phenomena can be unified into a single negative mass fluid. The model is a modified $\Lambda$CDM cosmology, and indicates that continuously-created negative masses can resemble the cosmological constant and can flatten the rotation curves of galaxies. The model leads to a cyclic universe with a time-variable Hubble parameter, potentially providing compatibility with the current tension that is emerging in cosmological measurements. In the first three-dimensional N-body simulations of negative mass matter in the scientific literature, this exotic material naturally forms haloes around galaxies that extend to several galactic radii. These haloes are not cuspy. The proposed cosmological model is therefore able to predict the observed distribution of dark matter in galaxies from first principles. The model makes several testable predictions and seems to have the potential to be consistent with observational evidence from distant supernovae, the cosmic microwave background, and galaxy clusters. These findings may imply that negative masses are a real and physical aspect of our Universe, or alternatively may imply the existence of a superseding theory that in some limit can be modelled by effective negative masses. Both cases lead to the surprising conclusion that the compelling puzzle of the dark Universe may have been due to a simple sign error.

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J. Farnes
Mon, 5 Nov 18
45/49

Comments: Accepted for publication in Astronomy and Astrophysics (A&A). Videos of the simulations are available online at: this https URL

The dynamics of asteroid rotation, governed by YORP effect: the kinematic ansatz [CL]

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http://arxiv.org/abs/1805.06304


The main motivation of this research is the analytical exploration of the dynamics of asteroid rotation when it moves in elliptic orbit through Space. According to the results of Efroimsky, Frouard (2016), various perturbations (collisions, close encounters, YORP effect) destabilize the rotation of a small body (asteroid), deviating it from the initial-current spin state. This yields evolution of the spin towards rotation about maximal-inertia axis due to the process of nutation relaxation or to the proper spin state corresponding to minimal energy with a fixed angular momentum. We consider in our research the aforementioned spin state of asteroid but additionally under non-vanishing influence of the effects of non-gravitational nature (YORP effect), which is destabilizing the asteroid rotation during its motion far from giant planets. Meanwhile, new solutions for asteroid rotation dynamics in case of negligible (time-dependent) applied torques have been obtained in our development. New method for solving Euler equations for rigid body rotation is suggested; an elegant example for evolution of spin towards the rotation about maximal-inertia axis is calculated.

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S. Ershkov and R. Shamin
Thu, 17 May 18
29/70

Comments: 23 pages, 4 figures; Keywords: tidal dissipation, asteroid rotation, YORP effect; article is accepted for publication in “Acta Astronautica” (14 May 2018), DOI 10.1016/j.actaastro.2018.05.023

Detection of Exoplanets Using the Transit Method [CL]

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http://arxiv.org/abs/1803.05565


I conducted differential photometry on a star GSC 3281-0800, a known host to exoplanet HAT-P-32b, using analysis software AstroImageJ. I plotted the measurements from a series of images taken during the transit, via ADU count given from an earth-based digital CCD camera. I was able to establish a definite light curve and learn more about the properties of this exoplanet.

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D. Afanasev
Fri, 16 Mar 2018
30/44

Comments: 7 pages, 6 figures

Stellar Absorption Line Analysis of Local Star-Forming Galaxies: The Relation Between Stellar Mass, Metallicity, Dust Attenuation and Star Formation Rate [GA]

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http://arxiv.org/abs/1708.07107


We analyze the optical continuum of star-forming galaxies in SDSS by fitting stacked spectra with stellar population synthesis models to investigate the relation between stellar mass, stellar metallicity, dust attenuation and star formation rate. We fit models calculated with star formation and chemical evolution histories that are derived empirically from multi-epoch observations of the stellar mass—star formation rate and the stellar mass—gas-phase metallicity relations, respectively. We also fit linear combinations of single burst models with a range of metallicities and ages. Star formation and chemical evolution histories are unconstrained for these models. The stellar mass—stellar metallicity relations obtained from the two methods agree with the relation measured from individual supergiant stars in nearby galaxies. These relations are also consistent with the relation obtained from emission line analysis of gas-phase metallicity after accounting for systematic offsets in the gas-phase-metallicity. We measure dust attenuation of the stellar continuum and show that its dependence on stellar mass and star formation rate is consistent with previously reported results derived from nebular emission lines. However, stellar continuum attenuation is smaller than nebular emission line attenuation. The continuum-to-nebular attenuation ratio depends on stellar mass and is smaller in more massive galaxies. Our consistent analysis of stellar continuum and nebular emission lines paves the way for a comprehensive investigation of stellar metallicities of star-forming and quiescent galaxies.

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H. Zahid, R. Kudritzki, C. Conroy, et. al.
Thu, 24 Aug 17
36/40

Comments: Accepted for publication in ApJ

Lα line of dark positronium as nongravitational detection of dark matter [CL]

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http://arxiv.org/abs/1704.08872


An attempt to predict the new atomic dark matter lines is done on the example of a dark lepton atom – positronium. Its Layman-alpha line with the energy near 3 GeV may be observable if the appropriate conditions realize. For this we have studied a {\gamma}-ray excess in the Center of our Galaxy. In principle, this excess may be produced by the L{\alpha} line of a dark positronium in the medium with Compton scattering. The possibility of observations of an annihilation line (E~300 TeV) of dark positronium is also predicted. Other proposals to observe the atomic dark matter are shortly described. Besides, H{\alpha} line (1.3{\mu}) of usual positronum must be observable in the direction on the Center of our Galaxy.

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V. Burdyuzha and V. Charugin
Mon, 1 May 17
16/46

Comments: 10 pages, 0 figures

A Free-Field Lagrangian for a Gauge Theory of the CPT Symmetry [CL]

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http://arxiv.org/abs/1703.10904


A simplified mathematical approach is presented and used to find a suitable free-field Lagrangian to complete previous work on constructing a gauge theory of CPT transformations.

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K. Koltko
Mon, 3 Apr 17
8/38

Comments: N/A

Anisotropic fluid spheres of embedding class one using Karmarkar condition [CL]

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http://arxiv.org/abs/1702.04192


We obtain a new anisotropic solution for spherically symmetric spacetimes by analysing of the Karmarkar embedding condition. For this purpose we construct a suitable form of one of the gravitational potentials to obtain a closed form solution. This form of the remaining gravitational potential allows us to solve the embedding equation and integrate the field equations. The resulting new anisotropic solution is well behaved which can be utilized to construct realistic static fluid spheres. Also we estimated masses and radii of fluid spheres for LMC X-4 and EXO 1785-248 by using observational data sets values. The obtained masses and radii show that our anisotropic solution can represent fluid spheres to a very good degree of accuracy.

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S. Maurya and S. Maharaj
Wed, 15 Feb 17
35/47

Comments: 16 pages, 11 figures

Cosmological histories from the Friedmann equation: The universe as a particle [CL]

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http://arxiv.org/abs/1606.09556


In this note, we discuss how possible expansion histories of the universe can be inferred in a simple way, for arbitrary energy contents. No new physical results are obtained, but the goal is rather to discuss an alternative way of writing the Friedmann equation in order to facilitate an intuitive understanding of the possible solutions; for students and researchers alike. As has been noted in passing by others, this specific form of the Friedmann equation allows us to view the universal expansion as a particle rolling along a frictionless track. Specific examples depicted include the current concordance cosmological model as well as a stable static universal model.

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E. Mortsell
Fri, 1 Jul 16
4/58

Comments: 11 pages, 5 figures. This is a note of predominantly pedagogical nature accepted for publication in European Journal of Physics

New analysis for the correlation between gravitational waves and neutrino detectors during SN1987A [CL]

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http://arxiv.org/abs/1603.05076


The two major problems, still associated with the SN1987A, are: a) the signals observed with the gravitational waves detectors, b) the duration of the collapse. Indeed, the sensitivity of the gravitational wave detectors seems to be small for detecting gravitational waves and, while some experimental data indicate a duration of order of hours, most theories assume that the collapse develops in a few seconds. Since recent data of the X-ray NuSTAR satellite show a clear evidence of an asymmetric collapse, we have revisited the experimental data recorded by the underground and gravitational wave detectors running during the SN1987A. New evidence is shown that confirms previous results, namely that the data recorded by the gravitational wave detectors running in Rome and in Maryland are strongly correlated with the data of both the Mont Blanc and the Kamiokande detectors, and that the correlation extends over a long period of time (one or two hours) centered at the Mont Blanc time. This result is obtained by comparing six \underline{ independent} files of data recorded by four different experiments located at intercontinental distances. The signals of the GW detectors preceded the signals of the underground detectors by a time of the order of one second.

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P. Galeotti and G. Pizzella
Thu, 17 Mar 16
32/58

Comments: 7 pages, 5 figures

Tachyonic approach to neutrino dark matter [CL]

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http://arxiv.org/abs/1602.02079


We apply a new approach based on three relativistic groups (bradyon, tachyon and instanton) forming the `Lorentz groupoid’ which allows, in particular, to consider tachyons without introducing imaginary masses and negative energies (related, as known, to violation of causality and unitarity). This leads to effectively scalar conglomerate composed of tachyonic neutrino and antineutrino spinor wave functions as a viable model for stationary dark matter. We also briefly discuss a relevant early non-stationary high-energy stage of the universe evolution.

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E. Mychelkin and M. Makukov
Mon, 8 Feb 16
18/53

Comments: Reported at 14th Marcel Grossmann Meeting (MG14), Rome, July 12-18, 2015. Submitted to conference proceedings

Cosmological model with dynamical curvature [CL]

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http://arxiv.org/abs/1601.07030


We generalize the recently introduced relativistic Lagrangian darkon fluid model (EPJ C (2015) 75:9) by starting with a self-gravitating geodesic fluid whose energy-momentum tensor is dust-like with a nontrivial energy flow. The corresponding covariant propagation and constraint equations are considered in a shear-free nonrelativistic limit whose analytic solutions determine the 1st-order relativistic correction to the spatial curvature. This leads to a cosmological model where the accelerated expansion of the Universe is driven by a time-dependent spatial curvature without the need for introducing any kind of dark energy. We derive the differential equation to be satisfied by the area distance for this model.

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P. Stichel
Wed, 27 Jan 16
52/57

Comments: N/A

Potential formation of three pyrimidine bases in interstellar regions [CL]

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http://arxiv.org/abs/1511.04343


Work on the chemical evolution of pre-biotic molecules remains incomplete since the major obstacle is the lack of adequate knowledge of rate coefficients of various reactions which take place in interstellar conditions. In this work, we study the possibility of forming three pyrimidine bases, namely, cytosine, uracil and thymine in interstellar regions. Our study reveals that the synthesis of uracil from cytosine and water is quite impossible under interstellar circumstances. For the synthesis of thymine, reaction between uracil and :CH2 is investigated. Since no other relevant pathways for the formation of uracil and thymine were available in the literature, we consider a large gas-grain chemical network to study the chemical evolution of cytosine in gas and ice phases. Our modeling result shows that cytosine would be produced in cold, dense interstellar conditions. However, presence of cytosine is yet to be established. We propose that a new molecule, namely, C4N3OH5 could be observable in the interstellar region. C4N3OH5 is a precursor (Z isomer of cytosine) of cytosine and far more abundant than cytosine. We hope that observation of this precursor molecule would enable us to estimate the abundance of cytosine in interstellar regions. We also carry out quantum chemical calculations to find out the vibrational as well as rotational transitions of this precursor molecule along with three pyrimidine bases.

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L. Majumdar, P. Gorai, A. Das, et. al.
Mon, 16 Nov 15
5/57

Comments: 38 pages, 7 figures, Accepted in Astrophysics and Space Science

Astrophysical Naturalness [CL]

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http://arxiv.org/abs/1511.00536


I suggest that stars introduce mass and density scales that lead to `naturalness’ in the Universe. Namely, two ratios of order unity. (1) The combination of the stellar mass scale, M*, with the Planck mass, MPl, and the Chandrasekhar mass leads to a ratio of order unity that reads NPl*=MPl/[(M*)(mp)^2]^{1/3}=0.15-3, where mp is the proton mass. (2) The ratio of the density scale, rhoD = 1/[(G)(tau)^2], introduced by the nuclear life time of stars, tau, to the density of the dark energy, rhoL, is NL*=rhoL/rhoD=10^{-7}-10^{5}. Although the range is large, it is critically much smaller than the 123 orders of magnitude usually referred to when rhoL is compered to the Planck density. In the pure fundamental particles domain there is no naturalness; either naturalness does not exist or there is a need for a new physics or new particles. The `Astrophysical Naturalness’ offers a third possibility: stars introduce the combinations of, or relations among, known fundamental quantities that lead to naturalness.

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N. Soker
Tue, 3 Nov 15
43/90

Comments: 8 pages

Precise model of Hawking radiation from the tunnelling mechanism [CL]

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http://arxiv.org/abs/1411.1213


We recently improved the famous result of Parikh and Wilczek, who found a probability of emission of Hawking radiation which is compatible with a non-strictly thermal spectrum, showing that such a probability of emission is really associated to two non-strictly thermal distributions for boson and fermions. Here we finalize the model by finding the correct value of the pre-factor of the Parikh and Wilczek probability of emission. In fact, that expression has the “of order” sign instead of the equality. In general, in this kind of leading order tunnelling calculations, the exponent arises indeed from the classical action and the pre-factor is an order Planck constant correction. But in the case of emissions of Hawking quanta, the variation of the Bekenstein-Hawking entropy is order 1 for an emitted particle having energy of order the Hawking temperature. As a consequence, the exponent in the Parikh and Wilczek probability of emission is order unity and one asks what is the real significance of that scaling if the pre-factor is unknown. Here we solve the problem assuming the unitarity of the black hole (BH) quantum evaporation and considering the natural correspondence between Hawking radiation and quasi-normal modes (QNMs) of excited BHs, in a “Bohr-like model” that we recently discussed in a series of papers. In that papers, QNMs are interpreted as natural BH quantum levels (the “electron states” in the “Bohr-like model”). Here we find the intriguing result that, although in general it is well approximated by 1, the pre-factor of the Parikh and Wilczek probability of emission depends on the BH quantum level n. We also write down an elegant expression of the probability of emission in terms of the BH quantum levels.

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C. Corda
Tue, 11 Aug 15
10/57

Comments: 13 pages, final version accepted for publication in Classical and Quantum Gravity. The results of arXiv:1304.1899 have been partially reviewed

Trying to understand dark matter [CL]

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http://arxiv.org/abs/1502.07375


We present some “back-of-the-envelope” calculations to try to understand cold dark matter, its searches, and extensions of the Standard Model. Some of the insights obtained from this exercise may be useful.

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B. Hoeneisen
Fri, 27 Feb 15
30/60

Comments: 16 pages, 1 figure

Dark Energy, Inflation, CMB Anisotropy and Polarization from Quantum Metric Fluctuations [CL]

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http://arxiv.org/abs/1410.1416


We propose a model of cosmological evolution of the early and late Universe which is consistent with observational data and naturally explains the origin of inflation and dark energy (DE). We show that the de Sitter accelerated expansion of the FLRW space with no matter fields (hereinafter, empty space) is its natural state, and the model does not require either a scalar field or cosmological constant or any other hypotheses. Mathematically, this is due to the fact that the de Sitter state is an exact solution of the rigorous, mathematically consistent equations of one-loop quantum gravity for the empty FLRW space that are finite off the mass shell. Physically, this is due to the fact that the natural quantum metric fluctuations have the backreaction effect on the FLRW background, forming a self-polarized de Sitter graviton condensate. The energy required to maintain the accelerated expansion is drawn from the graviton vacuum. At the start and the end of cosmological evolution, the Universe is assumed to be empty, which explains the origin of inflation and DE. This scenario is consistent with observational data. The Universe starts and ends with de Sitter expansion but the evolutionary process runs in these cases in opposite directions. It leads to the prediction that the signs of the parameter 1+w should be opposite in both cases, and this fact is consistent with observations. The fluctuations of the number of gravitons lead to fluctuations of their energy density which in turn leads to the observed CMB temperature anisotropy of the order of 10^-5 and CMB polarization. In the frame of this scenario, it is not a hypothetical scalar field that generates inflation and relic gravitational waves but on the contrary, the gravitational waves (gravitons) generate DE, inflation, CMB anisotropy and polarization.

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L. Marochnik and D. Usikov
Tue, 7 Oct 14
29/69

Comments: 11 pages

Constraining Parameters of Generalized Cosmic Chaplygin Gas in Loop Quantum Cosmology [CL]

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http://arxiv.org/abs/1409.7057


We have assumed the FRW universe in loop quantum cosmology (LQC) model filled with the dark matter and the Generalized Cosmic Chaplygin gas (GCCG) type dark energy where dark matter follows the linear equation of state. We present the Hubble parameter in terms of the observable parameters $\Omega_{m0}$ and $H_{0}$ with the redshift $z$ and the other parameters like $A$, $B$, $w_{m}$, $ \omega$ and $\alpha$ which coming from our model. From Stern data set (12 points)\& SNe Type Ia 292 data (from \cite{Riess1,Riess2,Astier}) we have obtained the bounds of the arbitrary parameters by minimizing the $\chi^{2}$ test. The best-fit values of the parameters are obtained by 66\%, 90\% and 99\% confidence levels. Next due to joint analysis with Stern+BAO and Stern+BAO+CMB observations, we have also obtained the bounds of the parameters ($A,B$) by fixing some other parameters $\alpha$, $w_{m}$ and $\omega$. From the best fit values of the parameters, we have obtained the distance modulus $\mu(z)$ for our theoretical GCCG model in LQC and from Supernovae Type Ia (union2 sample 552 data from [\cite{Amanullah}] \& Riess 292 data from [\cite{Riess1,Riess2,Astier}]), we have concluded that our model is in agreement with the Supernovae Type Ia sample data. In addition, we have investigated in details about the various types of Future Singularities that may be formed in this model and it is notable that our model is completely free from any types of future singularities.

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C. Ranjit and U. Debnath
Thu, 25 Sep 14
5/58

Comments: 36 pages, 15 figures, Accepted in Astrophysics and Space Science (2014). arXiv admin note: substantial text overlap with arXiv:1206.0507, arXiv:1304.6713, arXiv:1406.3043

Accretion of Dark Energy onto Higher Dimensional Charged BTZ Black Hole [CL]

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http://arxiv.org/abs/1409.4651


In this work, we have studied the accretion of $(n+2)$-dimensional charged BTZ black hole (BH). The critical point and square speed of sound have been obtained. The mass of the BTZ BH has been calculated and we have observed that the mass of the BTZ BH is related with square root of the energy density of dark energy which accretes onto BH in our accelerating FRW universe. We have assumed modified Chaplygin gas (MCG) as a candidate of dark energy which accretes onto BH and we have found the expression of BTZ BH mass. Since in our solution of MCG, this model generates only quintessence dark energy (not phantom) and so BTZ BH mass increases during the whole evolution of the accelerating universe. Next we have assumed 5 kinds of parametrizations of well known dark energy models. These models generate both quintessence and phantom scenarios i.e., phantom crossing models. So if these dark energies accrete onto the BTZ BH, then in quintessence stage, BH mass increases upto a certain value (finite value) and then decreases to a certain finite value for phantom stage during whole evolution of the universe. We have shown these results graphically.

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U. Debnath
Wed, 17 Sep 14
25/67

Comments: 15 pages, 6 figures. arXiv admin note: substantial text overlap with arXiv:1312.7462; and text overlap with arXiv:1007.2704 by other authors

On the Einstein-Cartan cosmology vs. Planck data [CL]

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http://arxiv.org/abs/1405.3435


The first comprehensive analyses of Planck data reveal that the cosmological model with dark energy and cold dark matter can satisfactorily explain the essential physical features of the expanding Universe. However, the inability to simultaneously fit large and small scale TT power spectrum, scalar power index smaller than one and the observations of the violation of the isotropy found by few statistical indicators of the CMB, urge theorists to search for explanations. We show that the model of the Einstein-Cartan cosmology with clustered dark matter halos and their corresponding clustered angular momenta coupled to torsion, can account for small scale – large scale discrepancy and larger peculiar velocities (bulk flows) for galaxy clusters. The nonvanishing total angular momentum (torsion) of the Universe enters as a negative effective density term in the Einstein-Cartan equations causing partial cancellation of the mass density. The integrated Sachs-Wolfe contribution of the Einstein-Cartan model is negative, thus it can provide partial cancellation of the large scale power of the TT CMB spectrum. The observed violation of the isotropy appears as a natural ingredient of the Einstein-Cartan model caused by the spin densities of light Majorana neutrinos in the early stage of the evolution of the Universe and bound to the lepton CP violation and matter-antimatter asymmetry.

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D. Palle
Thu, 15 May 14
34/55

Comments: 12 pages, 4 figures, 21 references; published version

Jeans instability and anti-screening in gravitational-antigravitational model of Universe [CL]

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http://arxiv.org/abs/1404.7122


The hypothesis of antigravitational interaction of elementary particles and antiparticles is considered on the basis of the simple two-component hydrodynamic model with gravitational repulsion and attraction. It is shown increasing of the Jeans instability rate, the presence of antiscreening and the dominative role of the gravitational repulsion as a possible mechanism for spatial separation of matter and antimatter in Universe, as well as the observable acceleration of the far galaxies. The sound wave is found for the two-component gravitational-antigravitational system, which starts for k = 0 in the case of annihilation neglecting. The suggested approach permits to reestablish the idea about baryon symmetry of Universe, causing its steady flatness of the large scale and accelerated Universe expansion.

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I. Gribov and S. Trigger
Wed, 30 Apr 14
31/68

Comments: 12 pages, 0 figures

The gravitational heat conduction and the hierarchical structure in solar interior [CL]

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http://arxiv.org/abs/1403.1759


With the assumption of local Tsallis equilibrium, the newly defined gravitational temperature is calculated in the solar interior, whose distribution curve can be divided into three parts, the solar core region, radiation region and convection region, in excellent agreement with the solar hierarchical structure. By generalizing the Fourier law, one new mechanism of heat conduction, based on the gradient of the gravitational temperature, is introduced into the astrophysical system. This mechanism is related to the self-gravity of such self-gravitating system whose characteristic scale is large enough. It perhaps plays an important role in the astrophysical system which, in the solar interior, leads to the heat accumulation at the bottom of the convection layer and then motivates the convection motion.

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Z. Yahui and D. Jiulin
Mon, 10 Mar 14
5/53

Earthś Mass Variability [CL]

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http://arxiv.org/abs/1402.3005


The perturbation of the Earth caused by variability of mass of Earth as additional reason with gravity of celestial bodies and shape of the Earth. The Earth eating and collecting matters from space and loss or eject matters to space through its flying in the space around the Sun. The source of the rising in the global sea level is not closed in global warming and icebergs, but the outer space is the additional important source for this rising. The Earth eats waters from space in unknown mechanism. The mass of the Earth become greater in November i.e. before transit apoapsis two months, and become latter in February i.e. after transit apoapsis to two months.

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R. Mawad
Fri, 14 Feb 14
31/42