scholarly journals A preliminary study about gravitational wave radiation and cosmic heat death

2021 ◽  
Vol 502 (2) ◽  
pp. 2787-2792
Author(s):  
Jianming Zhang ◽  
Qiyue Qian ◽  
Yiqing Guo ◽  
Xin Wang ◽  
Xiao-Dong Li
Keyword(s):  
Dark Matter ◽  
Time Scale ◽  
Mechanical Energy ◽  
Wave Radiation ◽  
Future Evolution ◽  
Black Hole Accretion ◽  
Mechanical Energy Dissipation ◽  
Heat Death ◽  
The Universe

ABSTRACT We study the role of gravitational waves (GW) in the heat death of the Universe. Due to the GW emission, in a very long period, dynamical systems in the universe suffer from persistent mechanical energy dissipation, evolving to a state of universal rest and death. With N-body simulations, we adopt a simple yet representative scheme to calculate the energy loss due to the GW emission. For current dark matter systems with mass ∼1012−1015 M⊙, we estimate their GW emission time-scale as ∼1019−1025 yr. This time-scale is significantly larger than any baryon processes in the Universe, but still ∼1080 times shorter than that of the Hawking radiation. We stress that our analysis could be invalid due to many unknowns such as the dynamical chaos, the quadrupole momentum of haloes, the angular momentum loss, the dynamic friction, the central black hole accretion, the dark matter decays or annihilations, the property of dark energy, and the future evolution of the Universe.

The Role of the Radial Orbit Instability in Dark Matter Halo Formation and Structure

2006 ◽  
Vol 2 (S235) ◽  
pp. 124-124
Author(s):  
J. M. Meyer ◽  
J. J. Dalcanton ◽  
T. R. Quinn ◽  
L. L. R. Williams ◽  
E. I. Barnes ◽  
...  
Keyword(s):  
Dark Matter ◽  
Density Profile ◽  
Dark Matter Halo ◽  
Dark Matter Halos ◽  
Radial Orbit ◽  
Profile Changes ◽  
Analytic Models ◽  
The Universe ◽  
Scale Length

AbstractFor nearly a decade, N-body simulations have revealed a nearly universal dark matter density profile. This density profile appears to be robust to changes in the overall density of the universe and the underlying power spectrum. Despite its universality, however, the physical origin of this profile has not yet been well understood. Semi-analytic models have suggested that scale lengths in dark matter halos may be determined by the onset of the radial orbit instability. We have tested this theory using N-body simulations of collapsing dark matter halos. The resulting halo structures are prolate in shape, due to the mild aspect of the instability. We find that the radial orbit instability sets a scale length at which the velocity dispersion changes rapidly from isotropic to radially anisotropic. Preliminary analysis suggests that this scale length is proportional to the radius at which the density profile changes shape, as is the case in the semi-analytic models; however, the coefficient of proportionality is different by a factor of ~2. We conclude that the radial orbit instability may be a key physical mechanism responsible for the nearly universal profiles of simulated dark matter halos.

scholarly journals Interactions in the dark sector of the Universe

2014 ◽  
Vol 11 (02) ◽  
pp. 1460014 ◽  
Author(s):  
Winfried Zimdahl
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Dark Sector ◽  
Future Evolution ◽  
Evolution Of The Universe ◽  
Λcdm Model ◽  
The Future ◽  
The Universe

Interactions inside the cosmological dark sector influence the cosmological dynamics. As a consequence, the future evolution of the Universe may be different from that predicted by the ΛCDM model. We review main features of several recently studied models with nongravitational couplings between dark matter and dark energy.

scholarly journals Entropy and Eschatology: A Comment on Kutrovátz's Paper "Heat Death in Ancient and Modern Thermodynamics"

2002 ◽  
Vol 09 (03) ◽  
pp. 291-299
Author(s):  
Milan M. Ćirković
Keyword(s):  
History Of Science ◽  
Anthropic Principle ◽  
Philosophical Tradition ◽  
Alternative Route ◽  
Future Evolution ◽  
Modern Times ◽  
Self Selection ◽  
History Of ◽  
Heat Death ◽  
The Universe

Recent intriguing discussion of heat death by Kutrovátz is critically examined. It is shown that there exists another way of answering the heat death puzzle, already present in the ancient philosophical tradition. This alternative route relies not only on the final duration of time (which has been re-discovered in modern times), but also on the notion of observational self-selection, which has received wide publicity in the last several decades under the title of the anthropic principle(s). We comment here on some further deficiencies of the account of Kutrovátz. Although the questions Kutrovátz raises are important and welcome, there are several errors in his treatment of cosmology which mar his account of the entire topic. In addition, the nascent discipline of physical eschatology holds promise of answering the basic explanatory task concerning the future evolution of the universe without appealing to metaphysics. This is a completely novel feature in the history of science, in contradistinction to the historical examples discussed by Kutrovátz.

scholarly journals Observational Role of Dark Matter in f(R) Models for Structure Formation

2018 ◽  
Vol 46 ◽  
pp. 1860045
Author(s):  
Murli Manohar Verma ◽  
Bal Krishna Yadav
Keyword(s):  
Dynamical System ◽  
Dark Matter ◽  
Fixed Points ◽  
Gravity Models ◽  
Stability Conditions ◽  
Cosmological Observations ◽  
General Relativistic ◽  
The Stability ◽  
The Universe

The fixed points for the dynamical system in the phase space have been calculated with dark matter in the [Formula: see text] gravity models. The stability conditions of these fixed points are obtained in the ongoing accelerated phase of the universe, and the values of the Hubble parameter and Ricci scalar are obtained for various evolutionary stages of the universe. We present a range of some modifications of general relativistic action consistent with the [Formula: see text]CDM model. We elaborate upon the fact that the upcoming cosmological observations would further constrain the bounds on the possible forms of [Formula: see text] with greater precision that could in turn constrain the search for dark matter in colliders.

scholarly journals DILATONIC DARK MATTER — A NEW PARADIGM

1998 ◽  
Vol 13 (02) ◽  
pp. 109-117 ◽  
Author(s):  
Y. M. CHO ◽  
Y. Y. KEUM
Keyword(s):  
Dark Matter ◽  
Cold Dark Matter ◽  
The Other ◽  
New Paradigm ◽  
Excellent Candidate ◽  
The Universe

We study the possibility that the dilaton plays the role of the dark matter of the universe. We find that the condition for the dilaton to be the dark matter of the universe strongly restricts its mass to be around 0.5 keV or 270 MeV. For the other mass ranges, the dilaton either undercloses or overcloses the universe. The 0.5 keV dilaton has the free-streaming distance of about 1.4 Mpc and becomes and excellent candidate of a warm dark matter, while the 270 MeV one has the free-streaming distance of about 7.4 pc and becomes a cold dark matter. We discuss the possible ways to detect the dilaton experimentally.

scholarly journals Heavy right-handed neutrino dark matter in left–right models

2017 ◽  
Vol 32 (15) ◽  
pp. 1740007 ◽  
Author(s):  
P. S. Bhupal Dev ◽  
Rabindra N. Mohapatra ◽  
Yongchao Zhang
Keyword(s):  
Dark Matter ◽  
Mass Range ◽  
Neutrino Masses ◽  
Seesaw Mechanism ◽  
Leptonic Sector ◽  
Active Neutrino ◽  
The Standard Model ◽  
The Stability ◽  
The Universe

We show that in a class of non-supersymmetric left–right extensions of the Standard Model (SM), the lightest right-handed neutrino (RHN) can play the role of thermal Dark Matter (DM) in the Universe for a wide mass range from TeV to PeV. Our model is based on the gauge group [Formula: see text] in which a heavy copy of the SM fermions is introduced and the stability of the RHN DM is guaranteed by an automatic [Formula: see text] symmetry present in the leptonic sector. In such models, the active neutrino masses are obtained via the type-II seesaw mechanism. We find a lower bound on the RHN DM mass of order TeV from relic density constraints, as well as a unitarity upper bound in the multi-TeV to PeV scale, depending on the entropy dilution factor. The RHN DM could be made long-lived by soft-breaking of the [Formula: see text] symmetry and provides a concrete example of decaying DM interpretation of the PeV neutrinos observed at IceCube.

scholarly journals Formation and early evolution of massive black holes

2006 ◽  
Vol 2 (S238) ◽  
pp. 73-82
Author(s):  
Piero Madau
Keyword(s):  
Black Holes ◽  
Dark Matter ◽  
Ionization State ◽  
First Stars ◽  
Massive Black Holes ◽  
X Ray ◽  
Hard Radiation ◽  
Low Mass ◽  
The Universe

AbstractThe astrophysical processes that led to the formation of the first seed black holes and to their growth into the supermassive variety that powers bright quasars at z ∼ 6 are poorly understood. In standard ΛCDM hierarchical cosmologies, the earliest massive holes (MBHs) likely formed at redshift z ≳ 15 at the centers of low-mass (M ≳ 5 × 105 M⊙) dark matter “minihalos”, and produced hard radiation by accretion. FUV/X-ray photons from such “miniquasars” may have permeated the universe more uniformly than EUV radiation, reduced gas clumping, and changed the chemistry of primordial gas. The role of accreting seed black holes in determining the thermal and ionization state of the intergalactic medium depends on the amount of cold and dense gas that forms and gets retained in protogalaxies after the formation of the first stars. The highest resolution N-body simulation to date of Galactic substructure shows that subhalos below the atomic cooling mass were very inefficient at forming stars.

scholarly journals A FRAMEWORK TO SIMULTANEOUSLY EXPLAIN TINY NEUTRINO MASS AND HUGE MISSING MASS PROBLEM OF THE UNIVERSE

2010 ◽  
Vol 25 (25) ◽  
pp. 2111-2120 ◽  
Author(s):  
YASAMAN FARZAN
Keyword(s):  
Dark Matter ◽  
Lower Bound ◽  
Neutrino Mass ◽  
Upper Bound ◽  
Low Energy ◽  
Neutrino Masses ◽  
Energy Scenario ◽  
The Masses ◽  
The Universe

A minimalistic scenario is developed to explain dark matter and tiny but nonzero neutrino masses. A new scalar called SLIM plays the role of the dark matter. Neutrinos achieve Majorana mass through a one-loop diagram. This scenario can be realized for both real and complex SLIM. Simultaneously explaining the neutrino mass and dark matter abundance constrains the scenario. In particular for real SLIM, an upper bound of a few MeV on the masses of the new particles and a lower bound on their coupling is obtained which make the scenario testable. The low energy scenario can be embedded within various SU (2)× U (1) symmetric models. A specific example is introduced and its phenomenological consequences are discussed.

Modelling ‘Life’ against ‘heat death’

2017 ◽  
Vol 17 (1) ◽  
pp. 61-69
Author(s):  
Michail Zak
Keyword(s):  
Dynamical Systems ◽  
Liouville Equation ◽  
Second Law Of Thermodynamics ◽  
Quantum Systems ◽  
Living Systems ◽  
Second Law ◽  
New Class ◽  
Heat Death ◽  
The Universe

AbstractThis work is inspired by the discovery of a new class of dynamical system described by ordinary differential equations coupled with their Liouville equation. These systems called self-controlled since the role of actuators is played by the probability produced by the Liouville equation. Following the Madelung equation that belongs to this class, non-Newtonian properties such as randomness, entanglement and probability interference typical for quantum systems have been described. Special attention was paid to the capability to violate the second law of thermodynamics, which makes these systems neither Newtonian, nor quantum. It has been shown that self-controlled dynamical systems can be linked to mathematical models of living systems. The discovery of isolated dynamical systems that can decrease entropy in violation of the second law of thermodynamics, and resemblances of these systems to livings suggests that ‘Life’ can slow down the ‘heat death’ of the Universe and that can be associated with the Purpose of Life.

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