On the Discrete Version of the Schwarzschild Problem

Vladimir Khatsymovsky

doi:10.3390/universe6100185

Abstract

We consider a Schwarzschild type solution in the discrete Regge calculus formulation of general relativity quantized within the path integral approach. Earlier, we found a mechanism of a loose fixation of the background scale of Regge lengths. This elementary length scale is defined by the Planck scale and some free parameter of such a quantum extension of the theory. Besides, Regge action was reduced to an expansion over metric variations between the tetrahedra and, in the main approximation, is a finite-difference form of the Hilbert–Einstein action. Using for the Schwarzschild problem a priori general non-spherically symmetrical ansatz, we get finite-difference equations for its discrete version. This defines a solution which at large distances is close to the continuum Schwarzschild geometry, and the metric and effective curvature at the center are cut off at the elementary length scale. Slow rotation can also be taken into account (Lense–Thirring-like metric). Thus, we get a general approach to the classical background in the quantum framework in zero order: it is an optimal starting point for the perturbative expansion of the theory, finite-difference equations are classical, and the elementary length scale has quantum origin. Singularities, if any, are resolved.

Highlights

The task of studying the object indicated by the title of the article is a special case of an attempt to describe a system with extreme and even singular gravitational fields
We get a general approach to the classical background in the quantum framework in zero order: it is an optimal starting point for the perturbative expansion of the theory, finite-difference equations are classical, and the elementary length scale has quantum origin
A distinctive feature of gravity as a geometry consists in the presence of a simple ansatz of geometry, which is described by a discrete set of variables

Summary

Introduction

The task of studying the object indicated by the title of the article is a special case of an attempt to describe a system with extreme and even singular gravitational fields Such a description, as is generally accepted, requires the involvement of quantum gravity and, in turn, can be considered in the broader context of studying quantum effects in the framework of a specific quantum-gravitational approach. From the formal viewpoint, general relativity (GR) is a non-renormalizable field theory, and divergences originate from the continuum nature of space-time. This leads us to expect the efficiency of discrete approaches [1].

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