arXiv subjects

Hwajin Eom

Publications and source records attributed to Hwajin Eom.

5 recordsLinked to original sources

arXiv2026

D-instanton Effects on the Holographic Weyl Semimetals

We investigate the effects of D-instantons on a holographic Weyl semimetal in a top-down approach. We find that the presence of D-instantons induces a novel phase transition from a Weyl semimetal to a gapped phase, providing a new mechanism for gap formation in strongly coupled systems. By analyzing the free energy of probe D7-brane embeddings, we construct the phase diagram in terms of the fermion mass, instanton density, and temperature, measured in units of the Weyl parameter. We show that, in addition to the conventional mass-driven transition associated with band inversion, the instanton density gives rise to a qualitatively different transition whose mechanism cannot be understood within the standard Dirac picture. We compute nonlinear electric conductivities from the regularity condition at the black hole horizon and demonstrate that the two types of transitions exhibit distinct transport behavior. In particular, the instanton-induced transition leads to a gapped phase with properties that differ from the conventional insulating phase. We also discuss possible interpretations of this phase in the boundary theory and comment on its relation to nonperturbative effects in strongly interacting systems.

hep-th↗

arXiv2022

Analytic approach to the formation of a three-dimensional black string from a dust cloud

In three-dimensional low-energy string theory, we study the formation of a black string from a dust cloud. We analytically obtain two distinct classes of exact solutions with arbitrary functions responsible for mass distributions of the dust cloud. The first and second kinds of solutions may describe collapsing dusts but the first kind is only for inhomogeneous dust distribution while the second kind has a homogeneous limit. The finite collapse time and the Israel junction conditions tell us that the first kind solution describes a desired collapsing phenomenon, whereas the scale factor in the inner spacetime for the second kind turns out to be trivial. In the first kind solution, specific collapsing models can be realized by choosing an appropriate inhomogeneous dust distribution consistent with the Israel junction conditions. Consequently, the inhomogeneous dust cloud eventually collapses to the black string although the homogeneous dust cloud does not guarantee the formation of the black string in our setting. The space-like curvature singularities occur at the finite collapse time and they can be cloaked by the horizon of the black string.

gr-qc↗

arXiv2022

Hawking-Page phase transition of the Schwarzschild AdS black hole with the effective Tolman temperature

A sufficiently large Schwarzschild AdS black hole with the Hawking temperature has a positive heat capacity and undergoes the Hawking-Page phase transition. Even though an arbitrary isothermal surface of a cavity is introduced, the essential features about the stability and phase transition of the Schwarzschild AdS black hole remain the same. In this paper, we study the stability and the Hawking-Page phase transition of the Schwarzschild AdS black hole by employing an alternative local temperature satisfying the Hartle-Hawking vacuum condition which states that the ingoing and outgoing fluxes vanish at the horizon so that the local temperature is naturally zero there. The different definition of the local temperature based on the stress tensor approach provides different types of stability and phase transition. For a AdS curvature radius below a critical one, the medium-sized black hole is found to be stable and the other small and large black holes turn out to be unstable regardless of the AdS curvature radius. Furthermore, we encounter various critical temperatures. The first one is for the Hawking-Page phase transition between the medium-sized black hole and thermal AdS, and the second one is for a phase transition between the large black hole and thermal AdS; however, the latter one is not essential because the large black hole and thermal AdS eventually collapse to the medium-sized black hole. Interestingly, we find an additional critical temperature related to the zeroth-order phase transition between the medium-sized black hole and thermal AdS. Consequently, the medium-sized black hole undergoes both the Hawking-Page phase transition and the zeroth-order phase transition.

gr-qc↗

arXiv2022

On thermal radiation of de Sitter space in the semiclassical Jackiw-Teitelboim model

In general, the Gibbons-Hawking temperature based on the Euclidean functional approach shows that de Sitter space in the Bunch-Davies vacuum is globally thermal. In the exactly soluble semiclassical Jackiw-Teitelboim model, we investigate thermal property of de Sitter space by taking into account the quantum back reaction of the geometry. The proper temperature of de Sitter space in the Bunch-Davies vacuum is found to vanish. In case of a certain quantum state breaking the de Sitter symmetry, de Sitter space can be made thermally exited; however, in this case the dilaton singularity cannot be avoided. Consequently, in the Jackiw-Teitelboim model the proper temperature of de Sitter space in the Bunch-Davies vacuum turns out to be zero and the Bunch-Davies vacuum is found to be the only physical vacuum without any naked singularities.

gr-qc↗

arXiv2021

Quantum radiation of a collapsing shell in three-dimensional AdS spacetime revisited

In three-dimensional AdS space, we consider the gravitational collapse of dust shell and then investigate the quantum radiation from the collapsing shell by employing the functional Schrödinger formalism. In the formation of the BTZ black hole, the interior geometry of the shell can be chosen as either the massless black hole or the global AdS space. In the incipient black hole limit, we obtain the wave function exactly from the time-dependent Schrödinger equation for a massless scalar field. Then, we show that the occupation number of excited states can be written by analytic expressions, and the radiation temperature is in agreement with the Hawking temperature, irrespective of the specific choice of the interior geometries.

gr-qc↗