Searcharxiv⌕ Search

arXiv subjects

Young-Jai Park

Publications and source records attributed to Young-Jai Park.

At least 19 recordsLinked to original sources

Statistical Entropy Based on the Generalized-Uncertainty-Principle-Induced Effective Metric

We investigate the statistical entropy of black holes within the framework of the generalized uncertainty principle (GUP) by employing effective metrics that incorporate leading-order and all-orders quantum gravitational corrections. We construct three distinct effective metrics induced by the GUP, which are derived from GUP-corrected temperature, entropy, and all-orders GUP corrections, and analyze their impact on black hole entropy using 't Hooft's brick wall method. Our results show that, despite the differences in the effective metrics and the corresponding ultraviolet cutoffs, the statistical entropy consistently satisfies the Bekenstein-Hawking area law when expressed in terms of an invariant (coordinate-independent) distance near the horizon. Furthermore, we demonstrate that the GUP naturally regularizes the ultraviolet divergence in the density of states, eliminating the need for artificial cutoffs and yielding finite entropy even when counting quantum states only in the vicinity of the event horizon. These findings highlight the universality and robustness of the area law under GUP modifications and provide new insights into the interplay between quantum gravity effects and black hole thermodynamics.

gr-qc↗

Tidal effects based on GUP-induced effective metric

In this paper, we study tidal forces in the Schwarzschild black hole whose metric includes explicitly a generalized uncertainty principle (GUP) effect. We also investigate interesting features of the geodesic equations and tidal effects dependent on the GUP parameter $α$ related to a minimum length. Then, by solving geodesic deviation equations explicitly with appropriate boundary conditions, we show that $α$ in the effective metric affects both the radial and angular components of the geodesic equation, particularly near the singularities.

gr-qc↗

GEMS embeddings of Hayward regular black holes in massless and massive gravities

After finding a solution for the Hayward regular black hole (HRBH) in massive gravity, we embed the (3+1)-dimensional HRBHs both in massless and in massive gravities into (5+2)- and (6+3)-dimensional Minkowski spacetimes, respectively. Here, massive gravity denotes that a graviton acquires a mass holographically by broken momentum conservation in the HRBH. The original HRBH has no holographically added gravitons, which we call massless. Making use of newly found embedding coordinates, we obtain desired Unruh temperatures and compare them with the Hawking and local fiducial temperatures, showing that the Unruh effect for a uniformly accelerated observer in a higher dimensional flat spacetime is equal to the Hawking effect for a fiducial observer in a black hole spacetime. We also obtain freely falling temperatures of the HRBHs in massless and massive gravities seen by freely falling observers, which remain finite even at the event horizons while becoming the Hawking temperatures in asymptotic infinity.

gr-qc↗

GUP corrected entropy of the Schwarzschild black hole in holographic massive gravity

We obtain the statistical entropy of a scalar field on the Schwarzschild black hole in holographic massive gravity by considering corrections on the density of quantum states to all orders in the Planck length from a generalized uncertainty principle (GUP). As a result, we find not only the generalized Bekenstein-Hawking entropy depending on holographically massive gravitons without any artificial cutoff, but also new additional correction terms, which are proportional to surface gravity. Moreover, we also observe that all order GUP corrected entropy is improved to have smaller GUP parameter $λ$ than the previous results.

gr-qc↗

GEMS embeddings of Schwarzschild and RN black holes in Painlevé-Gullstrand spacetimes

Making use of the higher dimensional global embedding Minkowski spacetime (GEMS), we embed (3+1)-dimensional Schwarzschild and Reissner-Nordström (RN) black holes written by the Painlevé-Gullstrand (PG) spacetimes, which have off-diagonal components in metrics, into (5+1)- and (5+2)-dimensional flat ones, respectively. As a result, we have shown the equivalence of the GEMS embeddings of the spacetimes with the diagonal and off-diagonal terms in metrics. Moreover, with the aid of their geodesic equations satisfying various boundary conditions in the flat embedded spacetimes, we directly obtain freely falling temperatures. We also show that freely falling temperatures in the PG spacetimes are well-defined beyond the event horizons, while they are equivalent to the Hawking temperatures, which are obtained in the original curved ones in the ranges between the horizon and the infinity. These will be helpful to study GEMS embeddings of more realistic Kerr, or rotating BTZ black holes.

gr-qc↗

Tidal effects in Schwarzschild black hole in holographic massive gravity

We investigate tidal effects produced in the spacetime of Schwarzschild black hole in holographic massive gravity, which has two additional mass parameters due to massive gravitons. As a result, we have obtained that massive gravitons affect the angular component of the tidal force, while the radial component has the same form with the one in massless gravity. On the other hand, by solving the geodesic deviation equations, we have found that radial components of two nearby geodesics keep tightening while falling into the black hole and after passing the event horizons get abruptly infinitely stretched due to massive gravitons. However, angular components of two nearby geodesics get stretched firstly, reach a peak and then get compressed while falling into the black hole. Moreover, we have also shown that the angular components are more easily deformed near the departure position as the mass of a black hole is smaller for a fixed graviton mass.

gr-qc↗

Local free-fall temperatures of charged BTZ black holes in massive gravity

We obtain a (3+3)-dimensional global flat embedding of the generalized (2+1) charged Bañados-Teitelboim-Zanelli black holes in massive gravity. We also study the local free-fall temperatures for freely falling observers starting from rest and investigate the effect of the charge and graviton mass in free-fall temperatures.

gr-qc↗

Stability issues of black hole in non-local gravity

We discuss stability issues of Schwarzschild black hole in non-local gravity. It is shown that the stability analysis of black hole for the unitary and renormalizable non-local gravity with $γ_2=-2γ_0$ cannot be performed in the Lichnerowicz operator approach. On the other hand, for the unitary and non-renormalizable case with $γ_2=0$, the black hole is stable against the metric perturbations. For non-unitary and renormalizable local gravity with $γ_2=-2γ_0={\rm const}$ (fourth-order gravity), the small black holes are unstable against the metric perturbations. This implies that what makes the problem difficult in stability analysis of black hole is the simultaneous requirement of unitarity and renormalizability around the Minkowski spacetime.

gr-qc↗

Generalized uncertainty principles and black hole temperatures in rainbow gravity

In this paper, we have obtained modified black hole temperatures in rainbow gravity by employing both the modified dispersion relation (MDR) and the three different types of generalized uncertainty principles (GUPs) including the extended uncertainty principle (EUP). We also investigate their thermodynamic stabilities of the modified Schwarzschild black hole according to the different GUPs.

physics.gen-ph↗

The origin of regular Newtonian potential in infinite derivative gravity

It turns out that the infinite derivative gravity (IDG) is ghost-free and renormalizable when one chooses the exponential of an entire function. For this IDG case, the corresponding Newtonian potential generated from the delta function is non-singular at the origin. However, we will explicitly show that the source generating this non-singular potential is given not by the delta-function due to the point-like source of mass, but by the Gaussian mass distribution. This explains clearly why the IDG with the exponential of an entire function yields the finite potential at the origin.

gr-qc↗

Preheating in the nonminimal derivative coupling to gravity

We revisit the reheating mechanism after the end of inflation in the non-minimal derivative coupling (NDC) to gravity with quadratic potential. This is because the inflaton of the NDC should describe the slow-roll inflation as well as the preheating stage after the end of inflation. We point out that the non-periodic inflaton solution implies the absence of parametric resonance, compared to the periodic oscillating inflaton for the canonical coupling (CC) to gravity. Furthermore, it is demonstrated that narrow and broad parametric resonances do not appear after the end of inflation in the NDC model by solving the differential equation numerically for the quantum field, which differs from the case of the the CC model obtained by solving Mathieu equation.

gr-qc↗

Thermodynamic stability of modified Schwarzschild-AdS black hole in rainbow gravity

In this paper, we have extended the previous study of the thermodynamics and phase transition of the Schwarzschild black hole in the rainbow gravity to the Schwarzschild-AdS black hole where metric depends on the energy of a probe. Making use of the Heisenberg uncertainty principle and the modified dispersion relation, we have obtained the modified local Hawking temperature and thermodynamic quantities in an isothermal cavity. Moreover, we carry out the analysis of constant temperature slices of a black hole. As a result, we have shown that there also exists another Hawking-Page-like phase transition in which case a locally stable small black hole tunnels into a globally stable large black hole as well as the standard Hawking-Page phase transition from a hot flat space to a black hole.

gr-qc↗

Einstein-singleton theory and its power spectra in de Sitter inflation

We study the Einstein-singleton theory during de Sitter inflation since it provides a way of degenerate fourth-order scalar theory. We obtain an exact solution expressed in terms of the exponential-integral function by solving the degenerate fourth-order scalar equation in de Sitter spacetime. Furthermore, we find that its power spectrum blows negatively up in the superhorizon limit, while it is negatively scale-invariant in the subhorizon limit. This suggests that the Einstein-singleton theory contains the ghost-instability and thus, it is not suitable for developing a slow-roll inflation model.

gr-qc↗

Local free-fall Temperature of modified Schwarzschild black hole in rainbow spacetime

We obtain a (5+1)-dimensional global flat embedding of modified Schwarzschild black hole in rainbow gravity. We show that local free-fall temperature in rainbow gravity, which depends on different energy $ω$ of a test particle, is finite at the event horizon for a freely falling observer, while local temperature is divergent at the event horizon for a fiducial observer. Moreover, these temperatures in rainbow gravity satisfy similar relations to those of the Schwarzschild black hole except overall factor $g(ω)$, which plays a key role of rainbow functions in this embedding approach.

gr-qc↗

Scale-invariant power spectra from a Weyl-invariant scalar-tensor theory

We obtain scale-invariant scalar and tensor power spectra from a Weyl-invariant scalar-tensor theory in de Sitter spacetime. This implies that the Weyl-invariance guarantees to implement the scale-invariance of power spectrum in de Sitter spacetime. We establish a deep connection between the Weyl-invariance of the action and scale-invariance of power spectrum in de Sitter spacetime.

gr-qc↗

Local free-fall Temperature of GMGHS Black Holes

We obtain a (5+1)-dimensional global flat embedding of the Gibbons-Maeda-Garfinkle-Horowitz-Strominger spacetime in Einstein frame, and a (5+2)-dimensional global flat embedding in string frame. We show that the local free-fall temperatures for freely falling observers in each frames are finite at the event horizons, while the local temperatures for fiducial observers are divergent. We also observe that the local free-fall temperatures differ between the two frames.

gr-qc↗

BRST quantization of a sixth-order derivative scalar field theory

We study a sixth order derivative scalar field model in Minkowski spacetime as a toy model of higher-derivative critical gravity theories. This model is consistently quantized when using the Becchi-Rouet-Stora-Tyutin (BRST) quantization scheme even though it does not show gauge symmetry manifestly. Imposing a BRST quartet generated by two scalars and ghosts, there remains a non-trivial subspace with positive norm. This might be interpreted as a Minkowskian dual version of the unitary truncation in the logarithmic conformal field theory.

hep-th↗