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
Physics, Particles & Fields
Nobuyoshi Komatsu
Summary: This study examines the connection between effective energy and thermostatistical quantities on a cosmological horizon, and finds that the derived free energy on the horizon is equivalent to the effective energy calculated from the Friedmann equation. The consistency between the two is interpreted as a holographic-like connection. The study also suggests that Padmanabhan's holographic equipartition law should lead to such a connection.
EUROPEAN PHYSICAL JOURNAL C
(2023)
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
Physics, Particles & Fields
A. I. Keskin, K. Kurt
Summary: In this study, the high-energy era of the universe is investigated using the constant-roll condition and a modified Friedmann equation based on a non-additive Tsallis entropic proposal. The constant-roll parameter is determined within the framework of observational data. Graphical analysis is performed on the non-additive Tsallis parameter for a wide range of power-term chaotic potentials, similar to phi(n), which includes some string-chaotic potential models. The analysis reveals that values of n in the range 0.5 < n < 1.2 point to a dynamical form of dark energy (quintessence) in the early universe, indicating their potential inclusion in string-chaotic potential models. The non-additive Tsallis parameter supports this by exhibiting negative values in the constant-roll field.
EUROPEAN PHYSICAL JOURNAL C
(2023)
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
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
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.
Review
Behavioral Sciences
T. W. Ross, A. Easton
Summary: This article explores the relationship between hippocampal cellular activity and event segmentation, as well as how we recall ongoing events. Through a interdisciplinary approach, it provides a new perspective and hypotheses for future research.
NEUROSCIENCE AND BIOBEHAVIORAL REVIEWS
(2022)
Article
Astronomy & Astrophysics
M. Muhsinath, V. T. Hassan Basari, Titus K. Mathew
Summary: The expansion law proposed by Padmanabhan suggests that the evolution of the horizon volume is determined by the difference between the degrees of freedom on the horizon and in the bulk. In this study, we modified the expansion law using the Kodama-Hayward temperature, which is the dynamical temperature of the horizon, and extended it to various gravity theories. Unlike the conventional approach, we expressed the horizon degrees of freedom in terms of surface energy and represented the modified expansion law in terms of cosmic components. The modified expansion law can be expressed as if the temperature of the dynamical horizon is T = H/2 pi.
GENERAL RELATIVITY AND GRAVITATION
(2023)
Article
Automation & Control Systems
Noboru Sakamoto
Summary: The paper addresses the existence problem of infinite horizon optimal control for exponentially stabilizable or stable systems. It identifies classes of nonlinear control systems for which infinite horizon optimal controls exist based on stability, stabilizability, detectability, and growth conditions. The result also applies to estimate the existence region of stable manifolds in the associated Hamiltonian systems. The findings have applications in analyzing the turnpike property in nonlinear finite horizon optimal control problems using a geometric approach.
Article
Astronomy & Astrophysics
Lorenzo Sebastiani
Summary: We investigate the thermodynamics of the apparent horizon in (non-flat) FLRW spacetime in different theories of modified gravity and in the presence of a perfect fluid. We focus on theories that have second order differential field equations on the FLRW background. Our findings suggest that it is possible to express the entropy solely in terms of the radius of the apparent horizon, which allows for the reconstruction of the gravitational lagrangian consistent with the first law.
PHYSICS OF THE DARK UNIVERSE
(2023)
Article
Computer Science, Theory & Methods
Junsheng Qiao
Summary: Recently, the concept of quasi-overlap functions on bounded lattices was introduced and studied by Paiva et al. This paper extends this research to bounded partially ordered sets and focuses on the constructions of quasi-overlap functions and their generalized forms. The truth values set of quasi-overlap functions is generalized from bounded lattices to bounded partially ordered sets. The constructions are based on Galois s-connections and various homomorphisms. The extensions preserve some basic properties of known quasi-overlap functions on different ordered sets.
FUZZY SETS AND SYSTEMS
(2022)
Article
Astronomy & Astrophysics
Eric J. Baxter, Blake D. Sherwin
Summary: This study discusses how to measure the Hubble constant using the CMB lensing power spectrum without relying on the sound horizon scale. It shows the potential for constraining H-0 using different methods, and suggests that improving constraints beyond a certain error level with CMB lensing alone may be challenging in the future.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Physics, Multidisciplinary
M. Z. Bhatti, Z. Yousaf, A. Rehman
Summary: In this manuscript, the validity of the horizon first law in the context of f(R,G)$f(R, \mathcal{G})$ gravity is evaluated. It is proposed that the energy and entropy of a black hole must be consistent with their respective integration values. The positivity of energy and entropy is shown to impose additional restrictions on the domain of f(R,G)$f(R, \mathcal{G})$ gravity.
FORTSCHRITTE DER PHYSIK-PROGRESS OF PHYSICS
(2023)
