arXiv subjects

Gopinath Guin

Publications and source records attributed to Gopinath Guin.

6 recordsLinked to original sources

arXiv2026

Quantum corrections to the black hole entropy using the brick wall model

It was suggested by 't Hooft that to avoid the divergence of the free energy or entropy of the probe fields, one has to introduce an infrared (IR) cutoff. This introduction of the IR cutoff, namely, the brick wall model, has been studied for the Schwarzschild black hole and has been shown by 't Hooft that to have the entropy of the order of Bekenstein-Hawking entropy, the cutoff must be of the order of Planck length. In this study, we investigated the brick wall model in the context of a Reissner-Nordstróm, quantum corrected Schwarzschild and quantum corrected Reissner-Nordström black holes. In particular, we have shown that the brick wall model can give logarithmic correction to the black hole entropy in the subleading order. The important aspect of our analysis is that we have not considered the near horizon approximation of the lapse function and get more accurate correction to the entropy. This corrected entropy has an important feature that it is larger than the usual Bekenstein-Hawking entropy which aligns with the result of Barrow entropy.

hep-th↗

arXiv2026

Entanglement Entropy and Complexity of Multicomponent Universe from Holography

Recent studies in \cite{Park:2020jio,Paul:2025gpk} have calculated various holographic information-theoretic quantities of the four-dimensional FLRW universe for different matter-dominated eras using the braneworld model of cosmology. These studies are done for a single matter component, which is a good toy model for understanding the entanglement properties of the universe. However, for a more realistic model, one should consider a scenario where our universe has coexisting matter components like radiation-dark matter or radiation-exotic matter, etc. In this work, we have presented a systematic way to study various holographic information-theoretic quantities, namely, entanglement entropy and complexity, of the FLRW universe in the presence of coexisting matter components. We have shown that the black brane geometry in the presence of $p$-brane gas indeed supports the existence of a universe with two-component matter sources. The second Israel junction condition, along with the Ryu-Takayanagi formula, is used to compute the time-dependent holographic entanglement entropy of the universe with coexisting radiation-dark matter and radiation-exotic matter. The expression of the time-dependent volume complexity is also evaluated in these scenarios. For both universes, these information-theoretic quantities show a clear radiation dependence in the early time and matter and exotic matter dominance in the late time, which is consistent with the thermal history of the universe \cite{WMAP:2010qai,WMAP:2010sfg,Planck:2014loa,Planck:2018vyg}.

hep-th↗

arXiv2026

One-point holographic correlator in the expanding universe

In this article, we have calculated the time-dependent thermal one-point function of massive operators within an expanding universe. We employ the Randall-Sundrum II braneworld model combined with a $p$-brane gas in the bulk, enabling us to represent various matter-dominated cosmological scenarios localised on the brane. Applying the geodesic formula introduced by Grinberg and Maldacena in \cite{Grinberg:2020fdj}, we have calculated the thermal one-point functions of massive operators within the universe. The time-dependent one-point functions for different matter-dominated universes, both single-component and multi-component, are derived from the brane's evolving radial position. The time-dependent positions of the branes have been obtained using the second Israel junction condition. Additionally, we have analyzed the early and late-time behaviors of the thermal one-point function across various matter-dominated universes.

hep-th↗

arXiv2025

Barrow holographic dark energy interacting model in the presence of radiation and matter

We have studied the effect of dynamical radiation in the interacting barrow holographic dark energy model for a non-flat universe. For both open and closed universes, we have obtained the evolution equation for the energy density parameters for dark energy, dark matter and radiation for four different kinds of interaction among the seven possible linear phenomenological interactions. We have then numerically solved those coupled differential equations to show their behaviour with the redshift parameter. Also, the dynamics of the dark energy equation of state parameter with redshift for different interaction models are shown. For all four interaction models, it is also found that for higher values of the Barrow exponent, the dark energy equation of state parameter shows a transition into the phantom region from the quintessence region in the early time, that is, for lower redshift values. We have also found different epochs corresponding to dark energy-dark matter, dark energy-radiation and dark matter-radiation crossings. These crossing points are also consistent with the thermal history of the universe. We have also obtained various observational constraints for different cosmological parameters for our interacting Barrow holographic dark matter model using the Cosmic chronometer, Baryon Acoustic Oscillator and Pantheon+ data sets. The constraint values of the Hubble parameter in our cosmological shows higher values compared to the $Λ$CDM model, therefore indicating towards a possible resolution to the Hubble tension problem.

gr-qc↗

arXiv2025

Renormalization group improved cosmology in the presence of a stiff matter era

In \href{https://link.aps.org/doi/10.1103/PhysRevD.92.103004}{Phys. Rev. D 92 (2015) 103004}, simple analytical solutions of the Friedman equations were obtained for a universe having stiff matter component in the early universe together with a dark matter, and a dark energy component. In this analysis, the universe is considered to be made of a dark fluid which behaves as a stiff matter in the early phase of the universe (when the internal energy dominates). It is also more logical to consider quantum gravitational effects in the early phase of the cosmological evolution. In this analysis, following \href{https://link.aps.org/doi/10.1103/PhysRevD.65.043508}{Phys. Rev. D 65 (2002) 043508}, we consider renormalization group improved modified Friedmann equations where the Newton's gravitational constant (G) and the cosmological constant (Λ) flows with the momentum scale of the universe. It is observed that for a universe undergoing a stiff matter era, radiation era, and matter era, inflation is absent in the early time regime of the universe when the flow of the Newton's gravitational constant and cosmological constant is under consideration. Using the identification of the momentum scale with the scale factor of the universe, we then explore the era $t>t_{\text{Pl}}$ which indicates a primarily matter dominated era with accelerated expansion due to the presence of dark energy. Finally, considering the total equation of state as a combination of linear equation of state along with a polytropic equation of state, we observe that after the Planck-time the universe can undergo an inflationary phase and we find out that the inflation is enhanced by quantum gravitational effects arising due to the consideration of renormalization group approach to quantum gravity

gr-qc↗

arXiv2025

Holographic entanglement entropy and complexity for the cosmological braneworld model

In a recent study \cite{Park:2020jio}, the time-dependent entanglement entropy of the universe undergoing expansion according to various power laws has been analyzed within the framework of the braneworld model. The results of the entanglement entropy in that paper take into account only the effects of a radiation and a matter-dominated universe. In this work, we have computed the time-dependent entanglement entropy and complexity of the FLRW universe in the presence of different matter sources (radiation, matter and some exotic matter). In contrast to the approach in \cite{Park:2020jio}, all the calculations in this paper have been carried out in a perturbative manner in the framework of braneworld model of cosmology. According to this model, our universe is situated on a brane and different matter sources appear on the brane due to the back reaction of different $p$-brane gas configurations in the bulk spacetime. By considering the bulk spacetime as a black brane geometry, we have considered different blackening factors corresponding to radiation, matter, and exotic matter and calculated entanglement entropy and complexity holographically. In the braneworld model, the universe's expansion is described by the brane's time-dependent radial position. This position is determined using the second Israel junction condition for various matter sources. The time evolution of entanglement entropy and complexity is then obtained by substituting this brane position. We have also shown the dependence of entanglement entropy and complexity on the cosmological time for all the different matter-dominated universes in the early and late time eras. Even though the calculations of holographic entanglement entropy and complexity are done perturbatively, the results remain consistent with those of \cite{Park:2020jio}.

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