arXiv subjects

Sojeong Cheong

Publications and source records attributed to Sojeong Cheong.

5 recordsLinked to original sources

arXiv2026

Investigation of the black-hole quantum atmosphere from the effective proper temperature

Hawking radiation may be regarded as originating at the event horizon; however, its spatial origin can instead be distributed over a finite region outside the horizon. In this paper, using an effective proper temperature, we investigate the quantum atmosphere within a tractable model based on the two-dimensional radial sector of $D$-dimensional Schwarzschild black holes. In the Hartle--Hawking state, the proper temperature is derived from the first law of thermodynamics in the presence of the conformal anomaly associated with Hawking radiation. In the Unruh state, we decompose the proper temperature into two chiral temperatures, $T_{\rm L}$ and $T_{\rm R}$, associated with the ingoing and outgoing fluxes, respectively. Demonstrating $T_{\rm R}$ as the effective proper temperature characterizing the outgoing Hawking flux with the proper temperature in the Hartle-Hawking state, we define the atmospheric radius effectively as the radial position at which the effective proper temperature attains its maximum. We then numerically compute the atmospheric radius of the quantum atmosphere for various spacetime dimensions and show that it decreases monotonically as the number of spacetime dimensions increases. In the large-dimensional limit, we find that the atmospheric radius remains separated from the horizon by a finite radial factor, indicating that the quantum atmosphere can persist as an extended exterior region in any dimension.

hep-th↗

arXiv2026

Extended symmetry of the Maxwell theory with a gauge coupling constant as a conserved charge

It has been proposed that any coupling constant in a covariant action can be treated as a conserved charge by promoting the coupling constant to auxiliary fields, typically realized by a scalar field paired with a higher-form gauge field. However, the procedure may break local symmetries, which can be explicitly shown in a simpler setting such as Maxwell theory. The Hamiltonian analysis of Maxwell theory with the auxiliary fields reveals that some of the constraints are second-class. Applying the BFT formalism, we restore the broken local symmetries and obtain a fully symmetric action defined on an extended configuration space. Despite the restoration of the local symmetries, no additional conserved charges are associated with the recovered symmetries. Consequently, the original theory turns out to be the gauge-fixed version of the extended theory.

hep-th↗

arXiv2025

Strong gravitational lensing effects of black holes with quantum hair

According to the no-hair theorem, stationary black holes are uniquely characterized by their mass, charge, and angular momentum. In this paper, we explore quantum hair by deriving the quantum-corrected black hole metric within the Barvinsky-Vilkovisky formalism. The quantum-corrected metric is obtained perturbatively around flat spacetime without assuming either the commutativity between the nonlocal operator and covariant derivatives or the nonlocal Gauss-Bonnet theorem, both of which are adopted in previous studies. Using this metric, we evaluate the deflection angle in the strong-field limit and compute the associated strong gravitational lensing observables, such as the angular separation and the relative magnification. Our results show that as the quantum hair, determined by the number of virtual massless quantum fields in the nonlocal effective action, increases, the photon sphere radius, the strong deflection angle, and the relative magnification all increase, whereas the angular separation decreases. As a result, we demonstrate that the quantum hair affects not only the black hole geometry but also its strong gravitational lensing effects.

gr-qc↗

arXiv2025

Einstein ring of dust shells with quantum hair

The information about the internal structure of a compact object is classically inaccessible to external observers. In this paper, we investigate how quantum corrections to gravitational fields can reveal the internal structure of compact objects composed of dust shells. Using an effective field theory approach to incorporate quantum corrections up to second order in curvature, we derive a quantum-corrected metric for $N$ uniformly spaced shells with equal surface mass density and then examine how these corrections manifest in the deflection angle for gravitational lensing. In particular, we mainly investigate quantum-corrected astrophysical observables such as the Einstein ring and image magnification. Compared to the classical scenario, the deflection angle and the corresponding Einstein angle differ by a term that depends explicitly on the number of dust shells, which play the role of quantum hair. Specifically, the quantum correction to them diminishes as $N$ increases, yet a finite deviation from the classical result remains even in the continuum limit $N\to\infty$. Consequently, our results show that the internal structures of compact objects with identical mass and radius can be distinguished by quantum hair through their lensing observables.

gr-qc↗

arXiv2024

Quantum geodesics reflecting the internal structure of stars composed of shells

In general relativity, an external observer cannot distinguish distinct internal structures between two spherically symmetric stars that have the same total mass $M$. However, when quantum corrections are taken into account, the external metrics of the stars will receive quantum corrections depending on their internal structures. In this paper, we obtain the quantum-corrected metrics at linear order in curvature for two spherically symmetric shells characterized by different internal structures: one with an empty interior and the other with $N$ internal shells. The dependence on the internal structures in the corrected metrics tells us that geodesics on these backgrounds would be deformed according to the internal structures. We conduct numerical computations to find out the angle of geodesic precession and show that the presence of internal structures amplifies the precession angle reflecting the discrepancy between the radial and orbital periods within the geodesic orbit. The amount of the precession angle increases monotonically as the number of internal shells increases and it eventually converges to a certain value for $N \to \infty$.

gr-qc↗