scholarly journals Accelerating cosmologies with nonlinear electrodynamics

2018 ◽  
Vol 96 (9) ◽  
pp. 992-998
Author(s):  
G.P. Singh ◽  
N. Hulke ◽  
Ashutosh Singh
Keyword(s):  
Cosmological Model ◽  
Apparent Horizon ◽  
Second Law Of Thermodynamics ◽  
Big Bang ◽  
Accelerated Expansion ◽  
Nonlinear Electrodynamics ◽  
Classical Stability ◽  
Initial Anisotropy ◽  
The Big Bang ◽  
The Universe

In this paper, we consider the framework of nonlinear electrodynamics in locally rotationally symmetric (LRS) Bianchi-I universe model composed of magnetic fluid. It has been shown that an accelerated universe expansion takes place if the nonlinear electromagnetic field is a source of gravitational field. In this model, after the big bang, the universe undergoes inflation and the accelerated expansion, dissipates the initial anisotropy of the curvature part without using a selected initial condition. Further validity of generalised second law of thermodynamics in the cosmological model enclosed by apparent horizon is investigated. We also discuss the classical stability of the cosmological model and observational viability of the model.

scholarly journals O UNIVERSO VIVO

2012 ◽  
Vol 19 (1.2) ◽  
Author(s):  
Francisco César de Sá Barreto ◽  
Luiz Paulo Ribeiro Vaz ◽  
Gabriel Armando Pellegatti Franco
Keyword(s):  
Cosmological Model ◽  
Chemical Elements ◽  
Big Bang ◽  
Living System ◽  
Irreversible Processes ◽  
Thermodynamics Of Irreversible Processes ◽  
Protons And Neutrons ◽  
Standard Cosmological Model ◽  
The Big Bang ◽  
The Universe

The standard cosmological model suggests that after the “Big Bang”, 14 billion of years ago, the universe entered a period of expansion and cooling. In the first one millionth of a second appear quarks, glúons, electrons and neutrinos, followed by the appearance of protons and neutrons. In this paper, we describe the “cosmic battle” between gravitation and energy, responsible for the lighter chemical elements and the formation of the stars. We describe the thermodynamics of irreversible processes of systems which are far away from equilibrium, a route that is followed by the universe, seen as a living system.

scholarly journals Augustine of Hippo’s Philosophy of Time Meets General Relativity

KronoScope ◽  
2014 ◽  
Vol 14 (1) ◽  
pp. 71-89 ◽  
Author(s):  
Ettore Minguzzi
Keyword(s):  
General Relativity ◽  
Cosmological Model ◽  
Degrees Of Freedom ◽  
Big Bang ◽  
Null Hypersurface ◽  
Philosophy Of Time ◽  
The Big Bang ◽  
The Universe

Abstract This paper proposes a cosmological model that uses a causality argument to solve the homogeneity and entropy problems of cosmology. In this model, a chronology violating region of spacetime causally precedes the remainder of the Universe, and a theorem establishes the existence of time functions precisely outside the chronology violating region. This model is shown to nicely reproduce Augustine of Hippo’s thought on time and the beginning of the Universe. In the model, the spacelike boundary representing the Big Bang is replaced by a null hypersurface at which the gravitational degrees of freedom are almost frozen while the matter and radiation content is highly homogeneous and thermalized.

scholarly journals Is the expansion of universe accelerating or the Photons decelerating?

2015 ◽  
Vol 3 (1) ◽  
pp. 40
Author(s):  
Hasmukh Tank
Keyword(s):  
Big Bang ◽  
Time Dilation ◽  
Red Shift ◽  
Light Curves ◽  
Accelerated Expansion ◽  
Gravitational Acceleration ◽  
Expansion Of The Universe ◽  
Pi Mesons ◽  
The Big Bang ◽  
The Universe

<p>Astronomical observations of the cosmological red-shift are currently interpreted in terms of ‘expansion of universe’ and ‘accelerated-expansion of the universe’, at the rate of <em>H<sub>0</sub> c</em>; here <em>H<sub>0</sub></em> is Hubble’s constant, and c is the speed of light. Whereas a straight-forward derivation presented here suggests that: rather it is the photon which is decelerating, at the rate of <em>H<sub>0</sub> c</em>. Such a deceleration of photons can be caused by virtual electrons, positrons and pi-mesons, contained in the extra galactic quantum vacuum, because: they do have gravitational-acceleration of the same order as <em>H<sub>0</sub> c</em> at their “surfaces”; or by decay of a photon into a lighter photon and a particle of mass <em>h H<sub>0</sub> / c<sup>2</sup></em>. Tired-light interpretations of the cosmological red-shift’ were so far considered as not compatible with the observations of ‘time-dilation of super-novae light-curves’; so in a paper titled: “Wave-theoretical insight into the relativistic ‘length-contraction’ and ‘time-dilation of super-novae light-curves’” (Tank, Hasmukh K. 2013), it has been already shown that any mechanism which can cause ‘cosmological red-shift’ will also cause ‘time-dilation of super-novae light-curves’.  Therefore, we now need not to remain confined to the Big-Bang model of cosmology.</p>

scholarly journals Thermodynamics of the viscous f(T,B) gravity in the new agegraphic dark energy model

2020 ◽  
Vol 35 (20) ◽  
pp. 2050166 ◽  
Author(s):  
A. Pourbagher ◽  
Alireza Amani
Keyword(s):  
Dark Energy ◽  
Hubble Parameter ◽  
Dark Energy Model ◽  
Apparent Horizon ◽  
Second Law Of Thermodynamics ◽  
Energy Model ◽  
Accelerated Expansion ◽  
Agegraphic Dark Energy ◽  
New Agegraphic Dark Energy ◽  
The Universe

In this paper, we first obtain the energy density by the approach of the new agegraphic dark energy model, and then the [Formula: see text] gravity model is studied as an alternative to the dark energy in a viscous fluid by flat-FRW background, in which [Formula: see text] and [Formula: see text] are torsion scalar and boundary term. The Friedmann equations will be obtained in the framework of modified teleparallel gravity by tetrad components. We consider that the universe dominates with components such as matter and dark energy by an interacting model. The Hubble parameter is parameterized by the power-law for the scale factor, and then we fit the corresponding Hubble parameter with observational data constraints. The variation of the equation of state (EoS) for dark energy is plotted as a function of the redshift parameter, and the accelerated expansion of the universe is explored. In what follows, the stability of the model is also studied on the base of the sound speed parameter. Finally, the generalized second law of thermodynamics is investigated by entropies of inside and on the boundary of the apparent horizon in thermodynamics equilibrium.

scholarly journals The Asymmetric Cosmic Time – The Key to a New Cosmological Model

2020 ◽  
Vol 2 (1) ◽  
pp. 97-111
Author(s):  
Horst Fritsch ◽  
Eberhard Schluecker
Keyword(s):  
Cosmological Model ◽  
Initial Conditions ◽  
Logical Consequence ◽  
Cosmic Time ◽  
Big Bang ◽  
Relativity Theory ◽  
Accelerated Expansion ◽  
Theory Of Relativity ◽  
De Sitter ◽  
The Universe

The asymmetric cosmic time is a logical consequence of the General Theory of Relativity (GR), if one demands that it should apply to the entire cosmos. From the simplest cosmological model that is consistent with the ART (Einstein-de Sitter model) thus follows the < Cosmic Time Hypothesis > (CTH), which offers solutions for many unsolved problems of cosmology that the current standard model of cosmology (ɅCDM model) cannot explain. According to the CTH, space, time and matter form a unit and develop evolutionarily according to identical, time-dependent laws. According to the CTH time has neither beginning nor end. The "big bang" disappears into the infinite past, which is why the universe manages without inflation. The accelerated expansion of the universe is also unlikely to occur if the SN-Ia measurement results are interpreted using the CTH. The cosmological constant Ʌ can then be omitted (Ʌ=0) and consequently no "dark energy" is needed. In addition, the CTH also provides interesting results on the topics: Initial conditions for hypotheses, stability of the expanding, flat universe (Ω=1), cosmic energy balance (is there negative energy ?), theory of earth expansion, unification of natural forces, Mach's principle. Should the CTH receive broad experimental confirmation, the GR could be extended to the "Universal Relativity Theory" (UR).

A holographic big bang?

2015 ◽  
Vol 24 (12) ◽  
pp. 1544029
Author(s):  
N. Afshordi ◽  
R. B. Mann ◽  
R. Pourhasan
Keyword(s):  
Cosmological Model ◽  
Big Bang ◽  
Initial Singularity ◽  
Scale Invariant ◽  
The Big Bang ◽  
The Universe ◽  
Important Test

We present a cosmological model in which the Universe emerges out of the collapse of a five-dimensional (5D) star as a spherical three-brane. The initial singularity of the big bang becomes hidden behind a causal horizon. Near scale-invariant primordial curvature perturbations can be induced on the brane via a thermal atmosphere that is in equilibrium with the brane, circumventing the need for a separate inflationary process and providing an important test of the model.

scholarly journals THE BIG BANG AS A PHASE TRANSITION

2005 ◽  
Vol 20 (10) ◽  
pp. 2037-2045 ◽  
Author(s):  
TOMÁŠ LIKO ◽  
PAUL S. WESSON
Keyword(s):  
Phase Transition ◽  
Cosmological Model ◽  
Big Bang ◽  
The Big Bang ◽  
The Universe

We study a five-dimensional cosmological model, which suggests that the universe began as a discontinuity in a scalar (Higgs-type) field, or alternatively as a conventional four-dimensional phase transition.

scholarly journals An Idea about Negative Cosmic Time in the Big Bang-Big Rip Cosmological Model

2021 ◽  
Author(s):  
Mohamed Abdalla Bakry ◽  
Ali Eid ◽  
A. Alkaoud
Keyword(s):  
Cosmological Model ◽  
Cosmic Time ◽  
Spherical Shape ◽  
Big Bang ◽  
Big Rip ◽  
The Moment ◽  
In The Beginning ◽  
The Big Bang ◽  
Negative Time ◽  
The Universe

In this article, we assume that the beginning of the universe was before the Big Bang. In the beginning, all matter in the universe was combined in an infinitesimal spherical shape. This sphere was compressed to an incomprehensible value for a period, and then exploded and expanded time and space. We are referring to the negative time before the Big Bang. The evolution of the universe before the Big Bang, passing through the moment of the explosion to the end of the universe at the Big Rip, has been studied. In this article, we try to answer the questions; did the universe exist before the Big Bang? What is the origin of the universe and how did it arise? What are the stages of the evolution of the universe until the moment of the Big Rip? What is the length of time for the stages of this development?

scholarly journals Thermodynamics of the $$R_{\mathrm{h}}=ct$$ Universe: a simplification of cosmic entropy

2021 ◽  
Vol 81 (3) ◽  
Author(s):  
Fulvio Melia
Keyword(s):  
Standard Model ◽  
Second Law Of Thermodynamics ◽  
Big Bang ◽  
Second Law ◽  
Arrow Of Time ◽  
Physical Conditions ◽  
The Standard Model ◽  
The Big Bang ◽  
Low Entropy ◽  
The Universe

AbstractIn the standard model of cosmology, the Universe began its expansion with an anomalously low entropy, which then grew dramatically to much larger values consistent with the physical conditions at decoupling, roughly 380,000 years after the Big Bang. There does not appear to be a viable explanation for this ‘unnatural’ history, other than via the generalized second law of thermodynamics (GSL), in which the entropy of the bulk, $$S_\mathrm{bulk}$$ S bulk , is combined with the entropy of the apparent (or gravitational) horizon, $$S_{\mathrm{h}}$$ S h . This is not completely satisfactory either, however, since this approach seems to require an inexplicable equilibrium between the bulk and horizon temperatures. In this paper, we explore the thermodynamics of an alternative cosmology known as the $$R_{\mathrm{h}}=ct$$ R h = c t universe, which has thus far been highly successful in resolving many other problems or inconsistencies in $$\varLambda $$ Λ CDM. We find that $$S_{\mathrm{bulk}}$$ S bulk is constant in this model, eliminating the so-called initial entropy problem simply and elegantly. The GSL may still be relevant, however, principally in selecting the arrow of time, given that $$S_{\mathrm{h}}\propto t^2$$ S h ∝ t 2 in this model.

A view of the universe before the big bang

2006 ◽  
Vol 190 ◽  
pp. 15-15
Author(s):  
D CASTELVECCHI
Keyword(s):  
Big Bang ◽  
The Big Bang ◽  
The Universe
Sign in / Sign up

Export Citation Format

Share Document