arXiv subjects

Chatchai Promsiri

Publications and source records attributed to Chatchai Promsiri.

11 recordsLinked to original sources

arXiv2026

Extended Thermodynamics and Renyi Entropy Beyond Fixed Central Charge

An outstanding problem in the framework of conformal thermodynamics concerns the interpretation of variations in the central charge $C$. In this paper, we construct a novel central-charge R\'enyi entropy via the Casini-Huerta-Myers (CHM) map by considering thermal CFTs on a hyperbolic cylinder within a fixed charge, field theory volume and central charge potential $(\tilde{Q},\mathcal{V},\mu_C)$ grand canonical ensemble. We demonstrate that the resulting entropy satisfies all four fundamental R\'enyi entropy inequalities throughout the admissible range of $\mu_C$, establishing its consistency as a genuine R\'enyi measure. Physically, this novel measure extends conventional R\'enyi entropy by capturing the degree of entanglement across a statistical ensemble of holographic CFTs with fluctuating degrees of freedom. Furthermore, our conformal thermodynamic analysis of near-extremal configurations reveals that residual entropy arises from the central charge sector rather than thermal excitations. The mass gap that separates the extremal state and the first thermal excitation introduces a characteristic temperature scale $\tilde{T}_*$, which translates via the CHM map into a distinguished characteristic R\'enyi index $n_*$. Crucially, we propose that $n_*$ separates the theory space into two qualitatively distinct statistical regimes: a dominant-theory regime ($n > n_*$) governed by the most probable CFT realizations, and a multi-theory regime ($n < n_*$) where a broader spectrum of fluctuating theories and higher-energy modular excitations becomes increasingly relevant.

hep-th↗

arXiv2025

Optical Signatures of q-deformed solution in Einstein-Maxwell-dilaton Gravity

We consider null geodesics in the background of spherically symmetric object in Einstein-Maxwell-Dilaton (EMD) theory with coupling function $f(\Phi)=e^{-2\lambda \Phi}$. The spherical solution is characteristically described by dilaton coupling $\lambda$, integrated dilaton flux $D$ and magnetic charge $P$. Then, we derive geodesic equations by using the Hamilton-Jacobi approach. The radial photon orbital equation on equatorial plane and effective potential are analyzed. The total deflection angle and trajectories of photon as a function of impact parameter $b$ are plotted with the variation of $\lambda,D$ and $P$. Furthermore, the relation between photon ring's width and the Lyapunov exponent is also explored. In addition, we use the Gralla-Lupsasca-Marrone (GLM) model to model intensity profile of optically thin accretion disk around the object. Hence, we construct optical images of the object surrounded by three distinct emission profiles. Lastly, we investigate the radius of innermost stable circular orbit (ISCO) for timelike geodesics.

gr-qc↗

arXiv2024

Observing Black Hole Phase Transitions in Extended Phase Space and Holographic Thermodynamics Approaches from Optical Features

The phase transitions of charged Anti-de Sitter (AdS) black holes are characterized by studying null geodesics in the vicinity of the critical curve of photon trajectories around black holes as well as their optical appearance as the black hole images. In the present work, the critical parameters including the orbital half-period $\tau$, the angular Lyapunov exponent $\lambda_L$, and the temporal Lyapunov exponent $\gamma_L$ are employed to characterize black hole phase transitions within both the extended phase space and holographic thermodynamics frameworks. Under certain conditions, we observe multi-valued function behaviors of these parameters as functions of bulk pressure and temperature in the respective approaches. We propose that $\tau$, $\lambda_L$, and $\gamma_L$ can serve as order parameters due to their discontinuous changes at first-order phase transitions. To validate this, we provide detailed analytical calculations demonstrating that these optical critical parameters follow scaling behavior near the critical phase transition point. Notably, the critical exponents for these parameters are found to be $1/2$, consistent with those of the van der Waals fluid. Our findings suggest that static and distant observers can study black hole thermodynamics by analyzing the images of regions around the black holes.

gr-qc↗

arXiv2023

Remarks on the light ring images and the optical appearance of hairy black holes in Einstein-Maxwell-dilaton gravity

The behaviors of null geodesics in the spherical symmetric black holes in Einstein-Maxwell-dilaton (EMD) theory with coupling function $f(\Phi)=e^{-2\alpha \Phi}$ are meticulously analyzed. We investigate the effects of coupling constant $\alpha$ on the effective potential of photon trajectories within three ranges, namely $0<\alpha <1$, $\alpha =1$ and $\alpha >1$. We find that the thicknesses of lensing and photon rings are smaller at larger $\alpha$ and fixed electric charge in the unit of mass $q$, whereas they are larger at fixed $\alpha$ and larger $q$. This behavior can be described by using the angular Lyapunov exponent $\gamma$ in the vicinity of the critical curve. Remarkably, the behaviors of photon trajectories are found to be more interesting when $\alpha>1$. Namely, the radius of the black hole shadow $R_\text{s}$ becomes to be smaller than the photon sphere radius $r_\text{ph}$ when $\alpha > 1$ and $q>q^*$. Moreover, $R_\text{s}$ goes to zero as $q$ saturates the extremal limit, beyond which the photon orbit becomes absent. Furthermore, we construct the optical appearance of black holes surrounded by optically and geometrically thin accretion disk with three cases of Gralla-Lupsasca-Marrone (GLM) emission profile. Our results indicate that the observed flux originating from the lensing and photon rings exhibits suppression as $\alpha$ increases, while it undergoes amplification with the increasing parameter $q$.

gr-qc↗

arXiv2023

Scalarization of planar anti de Sitter charged black holes in Einstein-Maxwell-Scalar theory

We construct scalarized planar charged black holes in Einstein-Maxwell-scalar (EMS) theory with the presence of a negative cosmological constant. Domains of existence of black hole solutions are given in term of nonminimally coupling constant $\alpha$. Perturbative stability of a scalarized black hole is investigated by calculating its quasinormal modes. Thermodynamic properties of the scalarized planar solution are also discussed. We observe no evidence of instability of the scalarized black holes. Moreover, we find that scalarized planar charged AdS black holes are thermodynamically preferred over scalar-free solutions in grand canonical and canonical ensembles. The transition between scalar-free solutions and scalarized solutions is found to be the thermal second order phase transition. The transition of these solutions shares some similar features with conductor-superconductor phase transition.

gr-qc↗

arXiv2022

Thermodynamics of Black Holes with R\'enyi Entropy from Classical Gravity

The nonextensive nature of black holes is one of the most intriguing discoveries. In fact, the black hole entropy is a nonextensive quantity that scales by its surface area at the event horizon. In our work, we extend the thermodynamic phase space of black holes by treating the nonextensive parameter of the R\'enyi entropy as the thermodynamic variable. Using Euler's theorem for a homogeneous function of the black holes' mass, the compatible Smarr formula and the first law of black hole thermodynamics can be obtained. It is also demonstrated that, by keeping the same form of the black hole mass, the R\'enyi temperature is straightforwardly defined as proposed in the literature. Since many different types of black holes can indeed be successfully treated with such a procedure, our consideration is fairly general. It is worthwhile to argue that the black hole thermodynamics in R\'enyi statistics is rooted from the relation among geometric quantities in the same way as the standard approach corresponding to the Gibbs-Boltzmann statistics. Even though our results are based on classical gravity, they may pave the way to derive the R\'enyi temperature using the notion of quantum field in curved spacetime.

gr-qc↗

arXiv2022

Emergent Phase, Thermodynamic Geometry and Criticality of Charged Black Holes from R\'enyi Statistics

Recently, a novel emergent phase can occur from thermodynamic consideration of the asymptotically flat Reissner-Nordstr\"om black hole (RN-AF) using R\'enyi statistics. We present an analysis of the thermodynamical and mechanical stabilities of the RN-AF in both the Gibbs-Boltzmann (GB) and the alternative R\'enyi statistics when charge $q$ and electrostatic potential $\phi$ are treated as pressure and volume, respectively. Interestingly, the emergent phase of the RN-AF can be both thermodynamically and mechanically stable in some range of parameters in the framework of R\'enyi thermodynamics. With the construction of the Maxwell equal area law in $q-\phi$ plane, the coexistence line between the near-extremal black hole phase and the emergent phase can be found in some values of charge which can be associated as the vapor pressure at which the liquid and gas phases coexist. In the aspect of thermodynamic geometry, the microscopic interaction between the black hole microstructures can be repulsive in the R\'enyi description. This implies that a novel correlation between the microstates of a self-gravitating system could be emerged via the nonextensive nature of long-range interaction systems. Finally, we also investigate the critical phenomena of the RN-AF in R\'enyi statistics compared to that of the van der Waals (vdW) fluid and find that the critical exponents of the relevant physical quantities of both systems are identical. This implies that both systems are in the same universality class of the phase transition.

hep-th↗

arXiv2021

Solid/Liquid Phase Transition and Heat Engine in Asymptotically Flat Schwarzschild Black Hole via the R\'enyi Extended Phase Space Approach

Recently, it has been found that, with the R\'enyi statistics, the asymptotically flat Schwarzschild black hole can be in thermal equilibrium with infinite heat reservior at a fixed temperature when its event horizon radius is larger than the characteristic length scale $L_\lambda=1/\sqrt{\pi \lambda}$, where $\lambda$ is the nonextensivity parameter. In the R\'enyi extended phase space with the $PdV$ work term, an off-shell free energy in the canonical ensemble with the thermodynamic volume as an order parameter is considered to identify a first-order Hawking-Page (HP) phase transition as a solid/liquid phase transition. It has the latent heat of fusion from solid (corresponding to thermal radiation) to liquid (corresponding to black hole) in the form of $\sim 1/\sqrt{\lambda}$; this is evident of the absence of the HP phase transition in the case of asymptotically flat Schwarzschild black hole from the GB statistics ($\lambda=0$). Moreover, we investigate the generalized second law of black hole thermodynamics (GSL) in R\'enyi statistics by considering the black hole as a working substance in heat engine. Interestingly, an efficiency $\eta$ of the black hole in a Carnot cycle takes the form $\eta_c=1-T_\text{C}/T_\text{H}$. This confirms the validity of the GSL in the R\'enyi extended phase space.

hep-th↗

arXiv2020

Thermodynamics and Van der Waals Phase Transition of Charged Black Holes in Flat Space via Rényi Statistics

The phase structure and critical phenomena of the 3+1 dimensional charged black holes in asymptotically flat spacetime are investigated in terms of thermodynamic properties within the Rényi statistics. With this approach as the non-extensive parameter above zero, we find that the charged black hole can be in thermodynamic equilibrium with surrounding thermal radiation, and have a Hawking-Page phase transition in the same way in the case of AdS charged black hole. This gives more evidence supporting the proposal that there exists an equivalence between the black hole thermodynamics in asymptotically flat spacetime via Rényi statistics and that in asymptotically AdS spacetime via Gibbs-Boltzmann statistics, proposed by Czinner et al. However, the present work also provides another aspect of supporting evidence through exploring the extended phase space within the Rényi statistics. Working on a modified version of Smarr formula, the thermodynamic pressure $P$ and volume $v$ of a charged black hole are found to be related to the non-extensive parameter. The resulting $P-v$ diagram indicates that the thermodynamics of charged black holes in asymptotically flat spacetime via Rényi statistics has the Van der Waals phase structure, equivalent to that in asymptotically AdS spacetime via Gibbs-Boltzmann statistics.

hep-th↗

arXiv2020

Thermodynamics and Phase Transition of Spherically Symmetric Black Hole in de Sitter Space from Rényi Statistics

Schwarzschild black holes in a de Sitter background were studied in terms of their thermodynamics based on the Rényi statistics. This led to thermodynamically stable black hole configurations for some certain range of black hole radii; namely within this range the corresponding black holes have positive heat capacity. Moreover, for a certain background temperature there can exist at most three configurations of black hole; one among which is thermodynamically stable. These configurations were investigated in terms of their free energies, resulting in the moderate-sized stable black hole configuration being the most preferred configuration. Furthermore, a specific condition on the Rényi non-extensive parameter is required if a given hot spacetime were to evolve thermally into the moderate-sized stable black hole.

gr-qc↗

arXiv2015

The Mixed Phase of Charged AdS Black holes

We study the mixed phase of charged AdS black hole and radiation when the total energy is fixed below the threshold to produce a stable charged black hole branch. The coexistence conditions for the charged AdS black hole and radiation are derived for the generic case when radiation particles carry charge. The phase diagram of the mixed phase is demonstrated for both fixed potential and charge ensemble. In the dual gauge picture, they correspond to the mixed phase of quark-gluon plasma~(QGP) and hadron gas in the fixed chemical potential and density ensemble respectively. In the nuclei and heavy ion collisions at intermediate energies, the mixed phase of exotic QGP and hadron gas could be produced. The mixed phase will condensate and evaporate into the hadron gas as the fireball expands.

hep-th↗