Article
Astronomy & Astrophysics
Ahmad Sheykhi
Summary: Barrow argued that quantum-gravitational effects may introduce fractal features on the black hole horizon and discussed the impact of Barrow entropy on cosmological equations, revealing modified Friedmann equations as well as examining the validity of the generalized second law of thermodynamics for the Universe enclosed by the apparent horizon.
Article
Astronomy & Astrophysics
Luis M. Sanchez, Hernando Quevedo
Summary: In this study, we investigate the relationship between gravity and thermodynamics in dynamic systems by considering the apparent horizon of the FLRW spacetime as a thermodynamic system. We derive the fundamental equation in the entropy representation and explore the consequences of satisfying classical laws of thermodynamics. Our investigation focuses on FLRW spacetimes with and without a cosmological constant. We find that the interpretation of the apparent horizon as an isolated thermodynamic system is only possible under certain conditions, as the analogy does not hold for all parameter values and the entire evolution of the horizon. However, we demonstrate that the generalized second law of thermodynamics remains valid.
Article
Astronomy & Astrophysics
Eirini Sourtzinou, Charis Anastopoulos
Summary: This paper investigates the thermodynamics of a small body near a black hole horizon using a first-principles analysis. The study focuses on a quantum ideal gas confined in a small box above the Schwarzschild horizon. The authors analyze the system in terms of free quantum fields and identify thermodynamic properties through the microcanonical distribution. They find that the effective dimension of the system changes as it approaches the horizon, and that the pressure is highly anisotropic. Additionally, they show that the approximation of quantum fields on a fixed background breaks down at microscopic distances from the horizon, requiring the inclusion of backreaction effects.
Article
Astronomy & Astrophysics
Kimet Jusufi, Ahmad Sheykhi
Summary: This article employs Verlinde's entropic force scenario and takes into account the zero-point length correction to the gravitational potential to extract the modified Friedmann equations. By considering the modified gravitational potential, logarithmic corrections to the entropy expression are found, leading to the derivation of the modified Friedman equations. Interestingly, the corrected Friedmann equations bear resemblance to the Friedmann equations in the braneworld scenario. Furthermore, a potential connection to the GUP principle is discussed, which could have implications on the Hubble tension. The evolution of the scale factor under the effect of zero-point length is also explored. Finally, considering the minimal length to be of the Planck order, the critical density and bouncing behavior of the universe with a critical density and minimal scale factor on the order of the Planck length are obtained.
Article
Astronomy & Astrophysics
Gopal Yadav, Nitin Joshi
Summary: In this study, the researchers analyzed the information paradox and its resolution in Schwarzschild de-Sitter black hole spacetime using the island proposal. They found that the black hole island is located inside the black hole event horizon, contrary to the universal result for eternal black holes, and the cosmological island is also located inside the cosmological event horizon. Moreover, they studied the effect of temperature on Page curves and observed that low-temperature black hole/de-Sitter patch exhibits Page curves at later times, while high-temperature black hole/de-Sitter patch shows the opposite behavior.
Article
Astronomy & Astrophysics
Sourav Bhattacharya, Nitin Joshi
Summary: Investigated the degradation of quantum entanglement in the Schwarzschild-de Sitter black hole spacetime, finding that entanglement or correlation degrades with increasing Hawking temperatures, but does not degrade and even increases when considering both horizons combined.
Article
Astronomy & Astrophysics
Shin'ichi Nojiri, Sergei D. Odintsov, Tanmoy Paul
Summary: In this study, the Bekenstein-Hawking entropy is modified and a new entropy function is developed to derive the usual FLRW equations for matter fluids with different equation of state parameters. The research finds that by using a general entropy based on the Bekenstein-Hawking entropy, the Friedmann equations of the apparent horizon cosmology can be modified, leading to interesting cosmological consequences.
Article
Physics, Particles & Fields
Bhramar Chatterjee, Narayan Banerjee
Summary: In this study, we examine radiation from cosmological apparent horizon in the FLRW model using a double-null coordinate setting. Due to the dynamic nature of spacetime, a Kodama vector is used as the dynamical time instead of a timelike Killing vector. By constructing the positive frequency modes of the Kodama vector across the horizon, we determine the temperature associated with the horizon based on the conditional probability of a signal reaching the central observer during crossing.
EUROPEAN PHYSICAL JOURNAL C
(2021)
Article
Physics, Particles & Fields
G. Lambiase, G. G. Luciano, A. Sheykhi
Summary: In this study, a new cosmological scenario is proposed based on Kaniadakis entropy and modified Friedmann equations. The research finds that the Kaniadakis parameter is constrained by observational limits and the correction term has a non-trivial effect on the growth of perturbations in the early stages of the Universe.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Astronomy & Astrophysics
Yong Xiao
Summary: This paper investigates the effects of higher curvature terms on black hole thermodynamics in modified theories of gravity. The corrections to the thermodynamics of the Schwarzschild black hole at the first order level are easily obtained without solving the modified black hole metric. The authors examine specific examples and discover some nonperturbative exact results by generalizing the first-order analysis.
Article
Multidisciplinary Sciences
Benoit Mahault, Evelyn Tang, Ramin Golestanian
Summary: Topology and stochastic thermodynamics are combined to formulate a fluctuation theorem for heat dissipation in vortex force fields, which is found to be topologically protected. The study demonstrates that entropy production in strongly fluctuating systems is quantized and controlled by a topological invariant, even when the probability distributions are non-Gaussian functions.
NATURE COMMUNICATIONS
(2022)
Article
Astronomy & Astrophysics
Prabir Rudra, Behnam Pourhassan
Summary: This study investigates the thermodynamic properties of the universe in the background of the generalized energy-momentum-squared gravity. By deriving the energy density of matter and performing thermodynamic analysis on two different models using the cosmic apparent horizon, it is found that stability analysis significantly constrains the parameter space of the models.
PHYSICS OF THE DARK UNIVERSE
(2021)
Article
Astronomy & Astrophysics
Everton M. C. Abreu, Jorge Ananias Neto
Summary: This work investigates the effects of three nongaussian entropies, namely, the modified Renyi entropy (MRE), the Sharma-Mittal entropy (SME), and the dual Kaniadakis entropy (DKE), on the violation of the generalized second law (GSL) of thermodynamics. It is found that the GSL may be violated when considering these extended entropies, and the parameters of these entropies need to be constrained to small values to obey the GSL. The study also reveals that for MRE, SME, and DKE, the GSL is not obeyed for small redshift values in the Lambda CDM cosmology.
Article
Physics, Nuclear
Abdul Jawad, Sidra Saleem, Saba Qummer
Summary: This study examines an extra driving term for the flat universe using Sharma Mittal entropy and Padmanabhan's holographic equipartition law, resulting in the generation of additional acceleration in the acceleration equation. By investigating various cosmological parameters through graphical methods, the study finds consistent results with current observational data and validates the generalized second law of thermodynamics in both models.
INTERNATIONAL JOURNAL OF MODERN PHYSICS A
(2021)
Article
Physics, Particles & Fields
Salvatore Capozziello, Mir Faizal, Mir Hameeda, Behnam Pourhassan, Vincenzo Salzano
Summary: Research investigates the effects of nonstandard corrections to Newtonian gravity on cosmological structure formation, focusing on how a logarithmic correction induced from nonlocal gravity modifies the clustering properties of galaxies and clusters of galaxies. Observations suggest a characteristic scale where such a logarithmic correction might be present at galactic scales, but statistical inferences at larger scales are much weaker and further investigations using a variety of cosmological and astrophysical probes are needed for fully reliable evidence.
EUROPEAN PHYSICAL JOURNAL C
(2021)
