Fully Self-Consistent Semiclassical Gravity

TL;DR

This paper introduces a fully self-consistent and empirically viable semiclassical gravity model where quantum matter fields evolve through objective collapse dynamics, coupling to classical gravity.

Contribution

It proposes the first self-consistent semiclassical gravity framework with quantum matter evolving via objective collapse, addressing previous self-consistency and empirical viability issues.

Findings

Framework successfully couples quantum matter to classical gravity.

Concrete example demonstrates model's feasibility.

Explores potential empirical consequences of the model.

Abstract

A theory of quantum gravity consists of a gravitational framework which, unlike general relativity, takes into account the quantum character of matter. In spite of impressive advances, no fully satisfactory, self-consistent and empirically viable theory with those characteristics has ever been constructed. A successful semiclassical gravity model, in which the classical Einstein tensor couples to the expectation value of the energy-momentum tensor of quantum matter fields, would, at the very least, constitute a useful stepping stone towards quantum gravity. However, not only no empirically viable semiclassical theory has ever been proposed, but the self-consistency of semiclassical gravity itself has been called into question repeatedly over the years. Here, we put forward a fully self-consistent, empirically viable semiclassical gravity framework, in which the expectation value of the energy-momentum tensor of a quantum field, evolving via a relativistic objective collapse dynamics, couples to a fully classical Einstein tensor. We present the general framework, a concrete example, and briefly explore possible empirical consequences of our model.