Entropy production due to spacetime fluctuations

TL;DR

This paper investigates how quantum spacetime fluctuations induce entropy production in a non-relativistic quantum system interacting with gravitational waves, using a fluctuation relation derived from the consistent histories approach.

Contribution

It introduces a fluctuation relation for a quantum system coupled to spacetime fluctuations, highlighting the inevitable entropy production due to quantum gravitational effects in the weak field limit.

Findings

Entropy is produced due to spacetime quantum fluctuations.

A fluctuation relation is formulated for the quantum system.

Quantum gravitational effects lead to thermodynamic irreversibility.

Abstract

Understanding the quantum nature of the gravitational field is undoubtedly one of the greatest challenges in theoretical physics. Despite significant progress, a complete and consistent theory remains elusive. However, in the weak field approximation -- where curvature effects are small -- we can explore some expected properties of such a theory. Particularly relevant to this study is the quantum nature of gravitational waves, which are represented as small perturbations in flat spacetime. In this framework, a quantum description of these perturbations, as a quantum field, is feasible, leading to the emergence of the graviton. Here we consider a non-relativistic quantum system interacting with such a field. We employ the consistent histories approach to quantum mechanics, which allows us to frame classical questions in a quantum context, to define a fluctuation relation for this system. As a result, thermodynamic entropy must be produced in the system due to its unavoidable interaction with the quantum fluctuations of spacetime.