Sunly Khimphun - Academia.edu (original) (raw)

Papers by Sunly Khimphun

Cornell University - arXiv, Oct 13, 2022

We investigate the regularized four-dimensional Einstein-Gauss-Bonnet (4D EGB) gravity with a non... more We investigate the regularized four-dimensional Einstein-Gauss-Bonnet (4D EGB) gravity with a non-minimal scalar coupling function, which is an extension of the regularized 4D EGB theory. By introducing non-minimal coupling to the Gauss-Bonnet term, we demonstrate the additional contribution to the dynamical equations which is otherwise absent in the dimensionally-regularized theory. Furthermore, we analyze the stability of the system by using the dynamical system approach based on fixed points. Then, we consider the time evolution to investigate the history of the universe and constraint with observational data to obtain the cosmological parameters of the model.

Physical Review D, 2016

In this paper, we investigate various types of Fubini instantons in the Dilatonic Einstein-Gauss-... more In this paper, we investigate various types of Fubini instantons in the Dilatonic Einstein-Gauss-Bonnet theory of gravitation which describes the decay of the vacuum state at a hilltop potential through tunneling without barrier. It is shown that the vacuum states are modified by the non-minimally coupled higher-curvature term. Accordingly, we present the new solutions which describe the tunneling from new vacuum states in anti-de Sitter and de Sitter backgrounds. The decay probabilities of the vacuum states are also influenced. We thus show that the semiclassical exponents can be decreased for specific parameter ranges, thereby increasing tunneling probability.

Journal of High Energy Physics

Four-dimensional cosmological models are studied on a boundary of a five-dimensional Anti-de Sitt... more Four-dimensional cosmological models are studied on a boundary of a five-dimensional Anti-de Sitter (AdS5) black hole with AdS Reissner-Nordström and scalar charged Reissner-Nordström black hole solutions, where we call the former a “Hairless” black hole and the latter a “Hairy” black hole. To obtain the Friedmann-Robertson-Walker (FRW) spacetime metric on the boundary of the AdS5 black hole, we employ Eddington-Finkelstein (EF) coordinates to the bulk geometry. We then derive modified Friedmann equations on a boundary of the AdS5 black hole via AdS/CFT correspondence and discuss its cosmological implications. The late-time acceleration of the universe is investigated in our models. The contributions coming from the bulk side is treated as dark energy source, and we perform MCMC analyses using observational data. Compared to the ΛCDM model, our models contain additional free parameters; therefore, to make a fair comparison, we use the Akaike information criterion (AIC) and the Bayes...

We construct SL(2, R) invariant in anisotropic medium, with a dual anisotropic charged black hole... more We construct SL(2, R) invariant in anisotropic medium, with a dual anisotropic charged black hole geometry in massive gravity. We show how to obtain SL(2, R) elements in terms of new degrees of freedom for Electromagnetic configuration, and construct the general expressions for conductivity with SL(2, R) invariant. The holographic conductivities can be calculated using horizon data in an external magnetic field, and we show the numerical results using the linear response theory. ∗e-mail : kpslourk@sogang.ac.kr †e-mail : bhl@sogang.ac.kr ‡e-mail : chanyong.park@apctp.org §e-mail : yunlong.zhang@apctp.org 1 ar X iv :1 70 5. 00 86 2v 1 [ he pth ] 2 M ay 2 01 7

EPJ Web of Conferences

There are many dark energy models having been investigated with constraint from observational dat... more There are many dark energy models having been investigated with constraint from observational data. The best dark energy candidate is ΛCDM model. In this work, our model has extended to include AdS/CFT correspondent, where the AdS black hole boundary exhibit the FLRW metric foliated with four-dimensional gravity theory, can lead to a modified Friedmann Equation contains extra parameter coming from 5D AdS (hairy) black hole, where such extension to ACDM can be considered. We obtained modified Friedmann equation from both 5D hairless and scalar hair black hole. The effect from extra dimension in hairless black hole solutions can be observed in the form of radiation. Also, it is interesting to see a non-trivial term emerges in scalar hair solution case. However in this study, we only consider Hairless black hole case for data constraint by using a join analysis of Supernovae, CMB and H0 measurement to obtain $ \chi _{\min }^2 $ . As a result, we compare this particular case with ACDM us...

We study dynamical condensation process in a holographic superconductor model with anisotropy. Th... more We study dynamical condensation process in a holographic superconductor model with anisotropy. The time-dependent numerical solution is constructed for the Einstein-Maxwell-dilaton theory with complex scalar in asymptotic AdS spacetime. The introduction of dilaton field generates the anisotropy in boundary spatial directions. In analogy of isotropic case, we have two black hole solutions below certain critical temperature T c , the anisotropic charged black hole with and without scalar hair, corresponding respectively to the supercooled normal phase and superconducting phase in the boundary theory. The instability of the supercooled anisotropic black hole will drive a small perturbation of the scalar field to rise exponentially, until the final stable hairy black hole configuration is reached. Via AdS/CFT correspondence, we extract time evolution of the condensate operator and anisotropic pressure of the boundary system. Both of them experience exponential growth and subsequent saturation, but with different relaxation time scales. Scalar quasinormal modes on anisotropic charged black holes are computed and shown to control the exponential growth of the condensate operator. We also present the final temperature and anisotropic pressure as functions of initial temperature and background anisotropy.

Journal of High Energy Physics

We investigate a massive gravity theory involving the SL(2, R) symmetry and anisotropy. Due to th... more We investigate a massive gravity theory involving the SL(2, R) symmetry and anisotropy. Due to the SL(2, R) invariance of the equations of motion, the complex conductivity of this model transforms covariantly under the SL(2, R) transformation and the ratio of DC conductivities in different spatial directions is preserved even after the SL(2, R) transformation. We further investigate AC and Hall conductivities by utilizing the Kubo formula. There exists a Drude-like peak in the region with a small anisotropy, while such a Drude peak disappears when anisotropy becomes large. We also show that the complex conductivity can have a cyclotron frequency pole even beyond the hydrodynamic limit.

Physics of the Dark Universe

Journal of High Energy Physics

We realize the weak momentum relaxation in Rindler fluid, which lives on the time-like cutoff sur... more We realize the weak momentum relaxation in Rindler fluid, which lives on the time-like cutoff surface in an accelerating frame of flat spacetime. The translational invariance is broken by massless scalar fields with weak strength. Both of the Ward identity and the momentum relaxation rate of Rindler fluid are obtained, with higher order correction in terms of the strength of momentum relaxation. The Rindler fluid with momentum relaxation could also be approached through the near horizon limit of cutoff AdS fluid with momentum relaxation, which lives on a finite time-like cutoff surface in Anti-de Sitter(AdS) spacetime, and further could be connected with the holographic conformal fluid living on AdS boundary at infinity. Thus, in the holographic Wilson renormalization group flow of the fluid/gravity correspondence with momentum relaxation, the Rindler fluid can be considered as the Infrared Radiation(IR) fixed point, and the holographic conformal fluid plays the role of the ultraviolet(UV) fixed point.

Physical Review D

In order to imitate anisotropic medium of a condensed matter system, we take into account an Eins... more In order to imitate anisotropic medium of a condensed matter system, we take into account an Einstein-Maxwell-dilaton-axion model as a dual gravity theory where the anisotropy is caused by different momentum relaxations. This gravity model allows an anisotropic charged black hole solution. On this background, we investigate how the linear responses of vector modes like electric, thermoelectric, and thermal conductivities rely on the anisotropy. We find that the electric conductivity in low frequency limit shows a Drude peak and that in the intermediate frequency regime it reveals the power law behavior. Especially, when the anisotropy increases the exponent of the power law becomes smaller. In addition, we find that there exist a critical value for the anisotropy at which the DC conductivity reaches to its maximum value.

Cornell University - arXiv, Oct 13, 2022

We investigate the regularized four-dimensional Einstein-Gauss-Bonnet (4D EGB) gravity with a non... more We investigate the regularized four-dimensional Einstein-Gauss-Bonnet (4D EGB) gravity with a non-minimal scalar coupling function, which is an extension of the regularized 4D EGB theory. By introducing non-minimal coupling to the Gauss-Bonnet term, we demonstrate the additional contribution to the dynamical equations which is otherwise absent in the dimensionally-regularized theory. Furthermore, we analyze the stability of the system by using the dynamical system approach based on fixed points. Then, we consider the time evolution to investigate the history of the universe and constraint with observational data to obtain the cosmological parameters of the model.

Physical Review D, 2016

In this paper, we investigate various types of Fubini instantons in the Dilatonic Einstein-Gauss-... more In this paper, we investigate various types of Fubini instantons in the Dilatonic Einstein-Gauss-Bonnet theory of gravitation which describes the decay of the vacuum state at a hilltop potential through tunneling without barrier. It is shown that the vacuum states are modified by the non-minimally coupled higher-curvature term. Accordingly, we present the new solutions which describe the tunneling from new vacuum states in anti-de Sitter and de Sitter backgrounds. The decay probabilities of the vacuum states are also influenced. We thus show that the semiclassical exponents can be decreased for specific parameter ranges, thereby increasing tunneling probability.

Journal of High Energy Physics

Four-dimensional cosmological models are studied on a boundary of a five-dimensional Anti-de Sitt... more Four-dimensional cosmological models are studied on a boundary of a five-dimensional Anti-de Sitter (AdS5) black hole with AdS Reissner-Nordström and scalar charged Reissner-Nordström black hole solutions, where we call the former a “Hairless” black hole and the latter a “Hairy” black hole. To obtain the Friedmann-Robertson-Walker (FRW) spacetime metric on the boundary of the AdS5 black hole, we employ Eddington-Finkelstein (EF) coordinates to the bulk geometry. We then derive modified Friedmann equations on a boundary of the AdS5 black hole via AdS/CFT correspondence and discuss its cosmological implications. The late-time acceleration of the universe is investigated in our models. The contributions coming from the bulk side is treated as dark energy source, and we perform MCMC analyses using observational data. Compared to the ΛCDM model, our models contain additional free parameters; therefore, to make a fair comparison, we use the Akaike information criterion (AIC) and the Bayes...

We construct SL(2, R) invariant in anisotropic medium, with a dual anisotropic charged black hole... more We construct SL(2, R) invariant in anisotropic medium, with a dual anisotropic charged black hole geometry in massive gravity. We show how to obtain SL(2, R) elements in terms of new degrees of freedom for Electromagnetic configuration, and construct the general expressions for conductivity with SL(2, R) invariant. The holographic conductivities can be calculated using horizon data in an external magnetic field, and we show the numerical results using the linear response theory. ∗e-mail : kpslourk@sogang.ac.kr †e-mail : bhl@sogang.ac.kr ‡e-mail : chanyong.park@apctp.org §e-mail : yunlong.zhang@apctp.org 1 ar X iv :1 70 5. 00 86 2v 1 [ he pth ] 2 M ay 2 01 7

EPJ Web of Conferences

There are many dark energy models having been investigated with constraint from observational dat... more There are many dark energy models having been investigated with constraint from observational data. The best dark energy candidate is ΛCDM model. In this work, our model has extended to include AdS/CFT correspondent, where the AdS black hole boundary exhibit the FLRW metric foliated with four-dimensional gravity theory, can lead to a modified Friedmann Equation contains extra parameter coming from 5D AdS (hairy) black hole, where such extension to ACDM can be considered. We obtained modified Friedmann equation from both 5D hairless and scalar hair black hole. The effect from extra dimension in hairless black hole solutions can be observed in the form of radiation. Also, it is interesting to see a non-trivial term emerges in scalar hair solution case. However in this study, we only consider Hairless black hole case for data constraint by using a join analysis of Supernovae, CMB and H0 measurement to obtain $ \chi _{\min }^2 $ . As a result, we compare this particular case with ACDM us...

We study dynamical condensation process in a holographic superconductor model with anisotropy. Th... more We study dynamical condensation process in a holographic superconductor model with anisotropy. The time-dependent numerical solution is constructed for the Einstein-Maxwell-dilaton theory with complex scalar in asymptotic AdS spacetime. The introduction of dilaton field generates the anisotropy in boundary spatial directions. In analogy of isotropic case, we have two black hole solutions below certain critical temperature T c , the anisotropic charged black hole with and without scalar hair, corresponding respectively to the supercooled normal phase and superconducting phase in the boundary theory. The instability of the supercooled anisotropic black hole will drive a small perturbation of the scalar field to rise exponentially, until the final stable hairy black hole configuration is reached. Via AdS/CFT correspondence, we extract time evolution of the condensate operator and anisotropic pressure of the boundary system. Both of them experience exponential growth and subsequent saturation, but with different relaxation time scales. Scalar quasinormal modes on anisotropic charged black holes are computed and shown to control the exponential growth of the condensate operator. We also present the final temperature and anisotropic pressure as functions of initial temperature and background anisotropy.

Journal of High Energy Physics

We investigate a massive gravity theory involving the SL(2, R) symmetry and anisotropy. Due to th... more We investigate a massive gravity theory involving the SL(2, R) symmetry and anisotropy. Due to the SL(2, R) invariance of the equations of motion, the complex conductivity of this model transforms covariantly under the SL(2, R) transformation and the ratio of DC conductivities in different spatial directions is preserved even after the SL(2, R) transformation. We further investigate AC and Hall conductivities by utilizing the Kubo formula. There exists a Drude-like peak in the region with a small anisotropy, while such a Drude peak disappears when anisotropy becomes large. We also show that the complex conductivity can have a cyclotron frequency pole even beyond the hydrodynamic limit.

Physics of the Dark Universe

Journal of High Energy Physics

We realize the weak momentum relaxation in Rindler fluid, which lives on the time-like cutoff sur... more We realize the weak momentum relaxation in Rindler fluid, which lives on the time-like cutoff surface in an accelerating frame of flat spacetime. The translational invariance is broken by massless scalar fields with weak strength. Both of the Ward identity and the momentum relaxation rate of Rindler fluid are obtained, with higher order correction in terms of the strength of momentum relaxation. The Rindler fluid with momentum relaxation could also be approached through the near horizon limit of cutoff AdS fluid with momentum relaxation, which lives on a finite time-like cutoff surface in Anti-de Sitter(AdS) spacetime, and further could be connected with the holographic conformal fluid living on AdS boundary at infinity. Thus, in the holographic Wilson renormalization group flow of the fluid/gravity correspondence with momentum relaxation, the Rindler fluid can be considered as the Infrared Radiation(IR) fixed point, and the holographic conformal fluid plays the role of the ultraviolet(UV) fixed point.

Physical Review D

In order to imitate anisotropic medium of a condensed matter system, we take into account an Eins... more In order to imitate anisotropic medium of a condensed matter system, we take into account an Einstein-Maxwell-dilaton-axion model as a dual gravity theory where the anisotropy is caused by different momentum relaxations. This gravity model allows an anisotropic charged black hole solution. On this background, we investigate how the linear responses of vector modes like electric, thermoelectric, and thermal conductivities rely on the anisotropy. We find that the electric conductivity in low frequency limit shows a Drude peak and that in the intermediate frequency regime it reveals the power law behavior. Especially, when the anisotropy increases the exponent of the power law becomes smaller. In addition, we find that there exist a critical value for the anisotropy at which the DC conductivity reaches to its maximum value.