scholarly journals Higher-derivative Lorentz-breaking dispersion relations: a thermal description

2021 ◽  
Vol 81 (9) ◽  
Author(s):  
A. A. Araújo Filho ◽  
A. Yu. Petrov
Keyword(s):  
Helmholtz Free Energy ◽  
Equations Of State ◽  
Planck Scale ◽  
Dispersion Relations ◽  
Microwave Background ◽  
Higher Derivative ◽  
Photon Gas ◽  
The Mean ◽  
The Universe ◽  
Do So

AbstractThis paper is devoted to study the thermal aspects of a photon gas within the context of Planck-scale-modified dispersion relations. We study the spectrum of radiation and the correction to the Stefan–Boltzmann law in different cases when the Lorentz symmetry is no longer preserved. Explicitly, we examine two models within the context of CPT-even and CPT-odd sectors respectively. To do so, three distinct scenarios of the Universe are considered: the Cosmic Microwave Background (CMB), the electroweak epoch, and the inflationary era. Moreover, the equations of state in these cases turn out to display a dependence on Lorentz-breaking parameters. Finally, we also provide for both theories the analyses of the Helmholtz free energy, the mean energy, the entropy and the heat capacity.

scholarly journals Large-Scale Structure of the Universe in Unstable Dark Matter Models

1988 ◽  
Vol 130 ◽  
pp. 293-300
Author(s):  
A.G. Doroshkevich ◽  
A.A. Klypin ◽  
M.U. Khlopov
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Large Scale ◽  
Numerical Models ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Microwave Background ◽  
Physical Background ◽  
The Mean ◽  
The Universe

Processes of the formation and the evolution of the large-scale structure are discussed in the framework of unstable dark matter models. Six numerical models are presented. The projected distribution of simulated galaxies on the sky, wedge diagrams, correlation functions and the mean linear scale of voids are presented. Physical background of the hypothesis of unstable particles and possible observational tests are discussed. The level of the microwave background fluctuations is estimated analytically. Special attention is given to late stage of supercluster evolution and galaxy formation.

Are we falling into the Virgo Cluster?

1981 ◽  
Vol 4 (2) ◽  
pp. 172-177 ◽  
Author(s):  
N. Visvanathan
Keyword(s):  
Hubble Constant ◽  
Virgo Cluster ◽  
Microwave Background ◽  
Mean Velocity ◽  
Distant Galaxies ◽  
Induced Motion ◽  
Density Perturbations ◽  
Peculiar Motion ◽  
The Mean ◽  
The Universe

One of the important discoveries of astronomy is that the Universe expands: distant galaxies have large recession velocities in direct proportion to their distances. Attempts to determine a global value for the constant of proportionality between the velocity and the distance (Hubble constant) are met with difficulties by the presence of peculiar, random and streaming motions in the local region. These peculiar motions are either of primordial origin or the effect of density perturbations. These affect the mean velocity of the nearby groups in the level of 50-100 km/sec (Tammann, Sandage and Yahil 1980). However, the expected peculiar gravitationally induced motion of the Local Group towards the Virgo cluster, could be large due to the high density contrast in that direction (Sciama 1967; de Vaucouleurs and Peters 1968; Sandage, Tammann and Hardy 1972; Jones 1976). This infall motion could be as high as 500 km/sec if the anisotropy of the microwave background is interpreted to have a component of our peculiar motion towards the Virgo cluster (Peebles 1971, Boughn, Cheng and Wilkinson 1981; Gorenstein and Smoot 1981).

Cosmic Density Fluctuations, Magnetic Fields and Gravitational Waves

1997 ◽  
Vol 12 (15) ◽  
pp. 1069-1076 ◽  
Author(s):  
M. D. Pollock
Keyword(s):  
Galaxy Formation ◽  
Background Radiation ◽  
Density Fluctuations ◽  
Microwave Background ◽  
Superstring Theory ◽  
Higher Derivative ◽  
Microwave Background Radiation ◽  
Dynamo Mechanism ◽  
Gravitational Wave Background ◽  
The Universe

It has previously been shown, for the heterotic superstring theory including higher-derivative terms ℛ2, how metric fluctuations, sufficient for galaxy formation in the Universe, arise as a consequence of the Heisenberg indeterminacy principle, applied to the dynamical auxiliary coordinate [Formula: see text] and its canonically conjugate momentum πξ, defined from the Friedmann space-time [Formula: see text]. This indeterminacy is distributed amongst the scalar, vector and tensor modes of the metric. Therefore, in addition to the fluctuations δρ/ρ in the matter, and in the cosmic microwave background radiation, there is a magnetic field, whose magnitude is estimated to agree approximately with the phenomenological value B c ~ 10-10 G required for the present-day intergalactic field (in the absence of a dynamo mechanism acting on a primordial field B s ≲ 10-17 G), and also a stochastic gravitational wave background, whose energy density must be bounded by the limit Ω gw ≲ 2.6×10-14h-2≈ 10-13 obtained by Krauss and White from the Sachs–Wolfe effect.

scholarly journals A thermodynamic origin for the Cohen-Kaplan-Nelson bound

2022 ◽  
Author(s):  
Satish Ramakrishna
Keyword(s):  
Free Energy ◽  
Helmholtz Free Energy ◽  
Canonical Ensemble ◽  
Quantum Field Theories ◽  
Quantum Field ◽  
Local Quantum ◽  
Hubble Radius ◽  
The Universe ◽  
Key Parameter ◽  
Do So

Abstract The Cohen-Kaplan-Nelson bound is imposed on the grounds of logical consistency (with classical General Relativity) upon local quantum field theories. This paper puts the bound into the context of a thermodynamic principle applicable to a field with a particular equation of state in an expanding universe. This is achieved without overtly appealing to either a decreasing density of states or a minimum coupling requirement, though they might still be consistent with the results described. We do so by defining an appropriate Helmholtz free energy which when extremized relative to a key parameter (the Hubble radius L) provides a scaling formula for the entropy with the Hubble radius (an exponent r used in the text). We deduce that the CKN bound is one possible solution to this extremization problem (with r=3/2), but there are others consistent with r=2. The paper establishes that the holographic principle applied to cosmology is consistent with minimizing the free energy of the universe in the canonical ensemble, upon the assumption that the ultraviolet cutoff is a function of the causal horizon scale.

scholarly journals Worship in Islam and Contemplation in God's Creation (An Analytical Study)

sjesr ◽  
2021 ◽  
Vol 4 (2) ◽  
pp. 295-298
Author(s):  
Dr. Samina Begum ◽  
Dr. Hafiz Muhammad Ibrar Ullah ◽  
Dr. Hashmat Begum
Keyword(s):  
Analytical Study ◽  
Human Being ◽  
The Earth ◽  
The World ◽  
The Mean ◽  
The One ◽  
Bear Witness ◽  
The Universe ◽  
Do So

The contemplation of God’s creation is one of the greatest forms of worship in Islam  every human being, when he observes the different scenes of this universe of colors and smells, enjoys seeing some of them so much that he longs to repeat this pleasure۔  It is not amazing, therefore, that countless Quranic verses give confidence this action and do so using a range of methods to appeal to every temperament and religious state. The mean is to switch people away from their dulled senses, awful habits, and monotonous familiarity, and encourage them to observe the signs of their Lord in the world with insight and vulnerable hearts. True Islamic contemplation can only spring from a mind that believes in God and a mind that submits to Him and His glorious Attributes. This is the unwavering faith of oneness (tawhÏd), which is to bear witness that the Almighty is the One and only God Who created, governs, and maintain the universe. Any other form of contemplation of the attractiveness and brilliance of the heavens and the earth would be measured atheism or polytheism (shirk) because the contemplator would not be distinguished, let alone admiring and express thanks to the Creator. In all religions, after beliefs, the highest importance is given to worship. Worship and contemplation are inseparable.

scholarly journals Trinity Relations in the Universe

1988 ◽  
Vol 130 ◽  
pp. 512-512
Author(s):  
Yasushi Suto ◽  
Roman Juskiewicz ◽  
Joseph Silk
Keyword(s):  
Perturbation Theory ◽  
Linear Perturbation ◽  
Mean Square ◽  
Mass Excess ◽  
Microwave Background ◽  
The Mean ◽  
Linear Perturbation Theory ◽  
Image Position ◽  
Density Irregularity ◽  
The Universe

On large scales where linear perturbation theory is valid, the mean square values of the mass excess , the peculiar velocity ν and the microwave background anisotropy due to the Sachs-Wolfe effect, are simply expressed in terms of the present-day power spectrum of the density irregularity P(k):

scholarly journals A thermodynamic origin for the Cohen-Kaplan-Nelson bound

2022 ◽  
Author(s):  
Satish Ramakrishna
Keyword(s):  
Free Energy ◽  
Helmholtz Free Energy ◽  
Canonical Ensemble ◽  
Quantum Field Theories ◽  
Quantum Field ◽  
Local Quantum ◽  
Hubble Radius ◽  
The Universe ◽  
Key Parameter ◽  
Do So

Abstract The Cohen-Kaplan-Nelson bound is imposed on the grounds of logical consistency (with classical General Relativity) upon local quantum field theories. This paper puts the bound into the context of a thermodynamic principle applicable to a field with a particular equation of state in an expanding universe. This is achieved without overtly appealing to either a decreasing density of states or a minimum coupling requirement, though they might still be consistent with the results described. We do so by defining an appropriate Helmholtz free energy which when extremized relative to a key parameter (the Hubble radius L) provides a scaling formula for the entropy with the Hubble radius (an exponent r used in the text). We deduce that the CKN bound is one possible solution to this extremization problem (with r = 3/2 ), but there are others consistent with r = 2. The paper establishes that the holographic principle applied to cosmology is consistent with minimizing the free energy of the universe in the canonical ensemble, upon the assumption that the ultraviolet cutoff is a function of the causal horizon scale.

scholarly journals Dark energy from geometrothermodynamics

2014 ◽  
Vol 11 (08) ◽  
pp. 1450071 ◽  
Author(s):  
Alessandro Bravetti ◽  
Orlando Luongo
Keyword(s):  
Dark Energy ◽  
Equations Of State ◽  
Contact Manifold ◽  
Early Time ◽  
Standard Pressure ◽  
Energy Equations ◽  
Limiting Case ◽  
The Universe ◽  
Thermodynamic Interaction ◽  
Do So

We investigate a general class of equations of state reproducing the dark energy effects in terms of geometric considerations on thermodynamic interaction. We infer cosmological solutions by combining thermodynamics with contact manifold and Riemannian geometry, showing that the standard ΛCDM model can be treated as a limiting case of a more general approach, providing early time departures as the universe expands. Thus, we interpret the microscopic nature of dark energy through the mathematical formalism of geometrothermodynamics (GTD). In particular, we investigate the thermodynamic nature of a class of cosmological models which reproduce how the universe is currently speeding up. To do so, we aim to describe thermodynamic equilibrium states of the universe through a particular equilibrium space, where the Riemannian metric g becomes a thermodynamical ruler between different states. The particular assumption we made is to consider the metric structure to be invariant under precise Legendre transformations. It turns out that any thermodynamic interaction is determined once the scalar curvature of the equilibrium manifold is known. The consequence of our recipe leads to a class of dark energy equations of state which relates standard pressure to the volume occupied by the fluid itself. In our picture, dark energy is thus determined from constant thermodynamic interaction on the manifold of GTD.

scholarly journals Constraints on the mean density of the Universe which follow from the theories of adiabatic and whirl perturbations

1978 ◽  
Vol 79 ◽  
pp. 404-405
Author(s):  
A. A. Kurskov ◽  
L. M. Ozernoy
Keyword(s):  
Large Scale ◽  
Background Radiation ◽  
Small Scale ◽  
Microwave Background ◽  
Scale Temperature ◽  
Microwave Background Radiation ◽  
Initial Spectrum ◽  
Density Perturbations ◽  
The Mean ◽  
The Universe

The aim of this communication is to investigate what constraints to the cosmological parameter Ω = 2qO can be obtained if one assumes that primaeval whirl motions or adiabatic density perturbations with an appropriate initial spectrum were responsible for the formation of large scale structure in the Universe. These constraints are readily obtained from the two conditions: (i) an upper limit to small scale temperature fluctuations of the microwave background radiation, and (ii) the requirement that the primaeval perturbations should be large enough in order to produce observed structures.

scholarly journals Cosmic Microwave Background as a Thermal Gas of SU(2) Photons: Implications for the High-z Cosmological Model and the Value of H0

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
Steffen Hahn ◽  
Ralf Hofmann
Keyword(s):  
Dark Matter ◽  
Cosmological Model ◽  
Cosmic Microwave Background ◽  
Cold Dark Matter ◽  
Formal Solution ◽  
Planck Scale ◽  
Low Frequency ◽  
Hubble Constant ◽  
Microwave Background ◽  
Photon Gas

Presently, we are facing a 3σ tension in the most basic cosmological parameter, the Hubble constant H0. This tension arises when fitting the Lambda-cold-dark-matter model (ΛCDM) to the high-precision temperature-temperature (TT) power spectrum of the Cosmic Microwave Background (CMB) and to local cosmological observations. We propose a resolution of this problem by postulating that the thermal photon gas of the CMB obeys an SU(2) rather than U(1) gauge principle, suggesting a high-z cosmological model which is void of dark-matter. Observationally, we rely on precise low-frequency intensity measurements in the CMB spectrum and on a recent model independent (low-z) extraction of the relation between the comoving sound horizon rs at the end of the baryon drag epoch and H0 (rsH0=const). We point out that the commonly employed condition for baryon-velocity freeze-out is imprecise, judged by a careful inspection of the formal solution to the associated Euler equation. As a consequence, the above-mentioned 3σ tension actually transforms into a 5σ discrepancy. To make contact with successful low-z  ΛCDM cosmology we propose an interpolation based on percolated/depercolated vortices of a Planck-scale axion condensate. For a first consistency test of such an all-z model we compute the angular scale of the sound horizon at photon decoupling.

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