Quantum, Gravity, and Geometry

TL;DR

This paper proposes a purely metric quantum gravity theory where matter quantum effects influence spacetime geometry, leading to the avoidance of initial singularities in black holes and the universe.

Contribution

It introduces a new purely metric quantum gravity framework that accounts for matter quantum effects without scalar fields, and explores its implications for black holes and cosmology.

Findings

Initial singularity can be avoided in black holes and the universe.

Quantum effects determine the conformal degree of freedom of spacetime.

The theory provides a consistent description of quantum gravity as a metric theory.

Abstract

Recently, it is shown that, the quantum effects of matter are well described by the conformal degree of freedom of the space-time metric. On the other hand, it is a wellknown fact that according to Einstein's gravity theory, gravity and geometry are interconnected. In the new quantum gravity theory, matter quantum effects completely determine the conformal degree of freedom of the space-time metric, while the causal structure of the space-time is determined by the gravitational effects of the matter, as well as the quantum effects through back reaction effects. This idea, previousely, is realized in the framework of scalar-tensor theories. In this work, it is shown that quantum gravity theory can also be realized as a purely metric theory. Such a theory is developed, its consequences and its properties are investigated. The theory is applied, then, to black holes and the radiation-dominated universe. It is shown that the initial singularity can be avoided.