Combining general relativity and quantum theory: points of conflict and contact

TL;DR

This paper discusses the fundamental conflicts and potential contact points between general relativity and quantum theory, focusing on spacetime microstructure, quantum cosmology, spacetime thermodynamics, and the cosmological constant problem.

Contribution

It reviews key issues and explores four specific themes where general relativity and quantum theory intersect, highlighting areas of contact and ongoing challenges.

Findings

Insights into the role of Planck length in spacetime microstructure

Discussion of quantum effects in cosmology and universe origin

Analysis of thermodynamics and entropy in spacetimes with horizons

Abstract

The issues related to bringing together the principles of general relativity and quantum theory are discussed. After briefly summarising the points of conflict between the two formalisms I focus on four specific themes in which some contact has been established in the past between GR and quantum field theory: (i) The role of planck length in the microstructure of spacetime (ii) The role of quantum effects in cosmology and origin of the universe (iii) The thermodynamics of spacetimes with horizons and especially the concept of entropy related to spacetime geometry (iv) The problem of the cosmological constant.