arXiv subjects

SangChul Yoon

Publications and source records attributed to SangChul Yoon.

7 recordsLinked to original sources

arXiv2019

From Lagrangian to Hamiltonian formulations of the Palatini action

We work on the Lagrangian and the Hamiltonian formulations of the Palatini action. In the Lagrangian formulation, we find that we need to assume the metric compatibility and the torsion zero or to assume the tetrad compatibility to describe General Relativity. In the Hamiltonian formulation, we obtain the Einstein's equations only with assuming the tetrad compatibility. The Hamiltonian from assuming the metric compatibility and the torsion zero should be used to quantize General Relativity.

gr-qc↗

arXiv2018

Lagrangian formulation of the Palatini action

We work on the Lagrangian formulation of the Palatini action. We find that we must assume the metric compatibility condition for the Palatini action to describe General Relativity, which condition should hold in quantization. We find that we must also assume one of the torsion zero condition or the tetrad compatibility condition. Our results will hold for any action in terms of the tetrad and the internal connection which describes General Relativity.

gr-qc↗

arXiv2017

Lagrangian and Hamiltonian formulations of the Palatini action

We derive the Ashtekar-Barbero variables in Loop Quantum Gravity(LQG) starting from the Palatini action. We find that we need either the torsion-free condition or the compatibility condition for the Palatini action to describe General Relativity.

gr-qc↗

arXiv2008

Anomaly-free representations of the holonomy-flux algebra

We work on the uniqueness, gr-qc/0504147, of representations of the holonomy-flux algebra in loop quantum gravity. We argue that for analytic diffeomorphisms, the flux operators can be only constants as functions on the configuration space in representations with no anomaly, which are zero in the standard representation.

gr-qc↗

arXiv2005

Hawking radiation and Quasinormal modes

The spectrum of Hawking radiation by quantum fields in the curved spacetime is continuous, so the explanation of Hawking radiation using quasinormal modes can be suspected to be impossible. We find that quasinormal modes do not explain the relation between the state observed in a region far away from a black hole and the short distance behavior of the state on the horizon.

gr-qc↗

arXiv2002

Black hole dynamics from thermodynamics in Anti-de Sitter space

We work on the relation between the local thermodynamic instability and the dynamical instability of large black holes in four-dimensional anti-de Sitter space proposed by Gubser and Mitra. We find that all perturbations suppressing the metric fluctuations at linear order become dynamically unstable when black holes lose the local thermodynamic stability. We discuss how dynamical instabilities can be explained by the Second Law of Thermodynamics.

hep-th↗

arXiv2001

From a Thick to a Thin Supergravity Domain Wall

Within D=4 N=1 supergravity theory we obtain an effective theory of the thin wall limit for a flat domain wall configuration, interpolating between isolated supersymmetric extrema of the matter potential. We focus on the Z_2 symmetric flat wall and derive the supersymmetric effective action both in the bulk and on the wall; in the thin wall limit the scalar field, forming the wall, is frozen, and provides the delta function domain wall source, while its fermionic partner decouples due to its large mass. In addition, the interaction between the gravitational supermultiplet and the interaction of the matter multiplet decouples on the wall. While the results are explicitly demonstrated within N=1 D=4 supergravity, we also provide a generalization of the result to D-dimensions.

hep-ph↗