arXiv subjects

Hassan Basari V. T.

Publications and source records attributed to Hassan Basari V. T..

7 recordsLinked to original sources

arXiv2024

Unified formalism for the emergence of space in non-equilibrium description

Previous studies indicate that the expansion law in emergence of space can be derived from the first law f thermodynamics. It has been proposed a unified formulation for the expansion law applicable to a general set of gravity theories in equilibrium description. In that formulation, which is based on the first law of thermodynamics, the non-equilibrium terms are ignored. Additionally, the structure of surface degrees of freedom in that formulation deviates from the standard notion, where $N_{sur} \ne 4S$ in general theories of gravity. This motivates us to develop a new unified formulation for the expansion law by incorporating non-equilibrium terms into the first law of thermodynamics. In this work, we formulate a unified expansion law in a non-equilibrium context, utilizing the first law of thermodynamics along with the definition of an effective Misner-Sharp energy. Compared to previous generalizations of the expansion law, our formulation reconciles the basic definition of surface degrees of freedom $N_{sur} = 4S$ for a general set of gravity theories. The unified expansion law in non-equilibrium not only highlights the direct relationship between the rate of areal volume and the difference in degrees of freedom between the surface and bulk $(N_{sur}-N_{bulk})$, but also reveals an inverse correlation with the density of surface degrees of freedom. We also demonstrate that the unified expansion law is instrumental in deriving the expansion law for a general set of gravity theories, including those with higher-order curvature corrections such as $f(R)$ theories of gravity, which require a non-equilibrium description.

gr-qc↗

arXiv2023

Unified formalism for the emergence of space from the first law of thermodynamics

We derive a unified expansion law for our universe from the first law of thermodynamics on the apparent horizon, where entropic evolution depicts the emergence of cosmic space. The derivation advances a general form for degrees of freedom on the surface and bulk, which provides a natural generalization for the expansion law proposed by Padmanabhan. The general expression for the surface degrees of freedom differs from the natural expectation, $ N_{sur }= 4S $ in the emergent gravity paradigm for general theories of gravity. The derivation also provides justification for the selection of Gibbons-Hawking temperature in the original expansion law and for the use of areal volume in the non-flat FRW universe. Since the unified expansion law exclusively depends on the form of entropy, the method is applicable to obtain the expansion law in any gravity theory without any additional ad hoc assumptions. From the general expansion law, we have obtained the expansion law corresponding to different theories of gravity like (n+1) Einstein, Gauss-Bonnet, Lovelock, and Horava-Lifshitz. We also obtained the expansion law for non-extensive entropy like Tsallis entropy from the unified expansion law.

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arXiv2022

Emergence of cosmic space in Tsallis modified gravity from equilibrium and non-equilibrium thermodynamic perspective

In this paper, we obtain the law of emergence with Tsallis entropy from the thermodynamic laws. We first derive the law of emergence from the equilibrium description of the unified first law and Clausius relation. However, it has been shown that considering Tsallis entropy as the horizon entropy, the Clausius relation $δQ=T dS$ does not hold due to non-equilibrium thermodynamics and is replaced by the entropy-balance relation $dS=\frac{δQ}{T}+d_{i}S$, where $d_iS$ is the additional entropy produced due to the irreversible thermodynamic process. Hence, we derive the law of emergence from the non-equilibrium description of thermodynamic laws. The comparison between the law of emergence in both cases shows that the law of emergence from the non-equilibrium approach describes the expansion of the universe in terms of the areal volume, unlike the effective volume in the equilibrium case. We have further shown that the law of emergence also satisfies the condition of the maximization of entropy for a de Sitter universe; thus, the entropy of the universe evolves to a bounded value in the asymptotic future.

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arXiv2022

Modified expansion law with Kodama-Hayward temperature for the horizon

The expansion law proposed by Padmanabhan suggests that the evolution of the volume of the horizon is due to the difference between the degrees of freedom on the horizon and the degrees of freedom in the bulk enclosed by the horizon. In formulating this law, Padmanabhan used the temperature, $T=H/2π$, for a dynamical expansion. In this work, we modified the expansion law using Kodama-Hayward temperature, the dynamical temperature, for the horizon, first in (3+1) Einstein's gravity and extended it to higher order gravity theories such as (n+1) Einstein gravity, Gauss-Bonnet gravity, and more general Lovelock gravity. Contrary to the conventional approach, we expressed degrees of freedom of the horizon in terms of the surface energy of the horizon. Also, we have expressed modified expansion law in terms of cosmic components. It then turns out that it is possible to express the modified expansion law in a form as if $T=H/2π$ is the temperature of the dynamical horizon.

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arXiv2022

Emergence of space and expansion of universe

According to the principle of emergence, the expansion of the universe can be explained as the emergence of space with the progress of cosmic time. We have analytically solved the equation of emergence proposed by Padmanabhan by assuming the Komar energy density $ρ+3P$ as a function of the Hubble parameter. The resulting model describes the evolution of the universe, which proceeds towards a final de Sitter state. Model parameters have been extracted using the cosmological observational data. Further, the horizon entropy evolution of the model has been studied. The model predicts a universe having a transition from a prior decelerated epoch to a late accelerated epoch and reasonably predicts the cosmological constant.

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arXiv2022

Emergence of cosmic space and its connection with thermodynamic principles

The recent research on the connection between gravity and thermodynamics suggests that gravity could be an emergent phenomenon. Following this, Padmanabhan proposed a novel idea that the expansion of the universe can be interpreted as equivalent to the emergence of space with the progress of cosmic time. In this approach, the expansion of the universe is described by what is known as the law of emergence, which states that the expansion of the universe is driven by the difference between the number of bulk and surface degrees of freedom in a region bounded by the Hubble radius. This principle correctly reproduces the standard evolution of a Friedmann universe. We establish the connection of the law of emergence, which is conceptually different from the conventional paradigm to describe cosmology, with other well-established results in thermodynamics. It has been shown that the law of emergence can be derived from the unified first law of thermodynamics, which can then be considered as the backbone of the law. However, the law of emergence is rich in structure than implied by the First law thermodynamics alone. It further explains the evolution of the universe towards a state of maximum horizon entropy. Following this, it can be considered that the first law of thermodynamics, along with the additional constraints imposed by the maximisation of the horizon entropy, can together lead to the law of emergence. In the present article, we first make a brief review of Padmanabhan's proposal and then studies its connection with the thermodynamics of the horizon in the context of Einstein's, Gauss-Bonnet, and more general Lovelock gravity theories.

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arXiv2021

Emergence of space from non-equilibrium thermodynamics in f(R) gravity

It has shown that the accelerated expansion of the FRW Universe can be explained as the quest towards the holographic equipartition ($N_{sur} = N_{bulk}$), satisfies the expansion law $\frac{dV}{dt} = l_{P}^{2} \left( N_{sur} - εN_{bulk} \right)$, from which one can derive the Friedmann equation of the FRW Universe in Einstein gravity \cite{paddy2012jun}. We introduce a generic derivation of the expansion law from the generalized first law of thermodynamics $-dE=TdS$ and $dE=TdS + WdV$. The generic derivation provides an expression for $N_{sur}$ in terms of entropy $S$ and the expansion law consistent with gravity theories having different entropy $S$, like Gauss-Bonnet and more general Lovelock gravity. We extended the same idea to the non-equilibrium situation and obtained the expansion law in f(R) gravity as a specific case. For this, we used the first law of thermodynamics in non-equilibrium description having the extra entropy production term $Td_{i}S.$

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