Quantum evolution in spacetime foam

TL;DR

This paper reviews how quantum fluctuations at the Planck scale create a foamlike spacetime structure that affects low-energy quantum fields, potentially observable through coherence loss and energy shifts.

Contribution

It introduces a model of spacetime foam with nontrivial topology affecting low-energy physics via a quantum bath and master equation approach.

Findings

Spacetime foam can cause loss of quantum coherence.

Quantum fields experience mode-dependent energy shifts.

Low-energy effective evolution can be modeled by a quantum bath.

Abstract

In this work, I review some aspects concerning the evolution of quantum low-energy fields in a foamlike spacetime, with involved topology at the Planck scale but with a smooth metric structure at large length scales, as follows. Quantum gravitational fluctuations may induce a minimum length thus introducing an additional source of uncertainty in physics. The existence of this resolution limit casts doubts on the metric structure of spacetime at the Planck scale and opens a doorway to nontrivial topologies, which may dominate Planck scale physics. This foamlike structure of spacetime may show up in low-energy physics through loss of quantum coherence and mode-dependent energy shifts, for instance, which might be observable. Spacetime foam introduces nonlocal interactions that can be modeled by a quantum bath, and low-energy fields evolve according to a master equation that displays such effects. Similar laws are also obtained for quantum mechanical systems evolving according to good real clocks, although the underlying Hamiltonian structure in this case establishes serious differences among both scenarios. Contents.--- Quantum fluctuations of the gravitational field; Spacetime foam; Loss of quantum coherence; Quantum bath; Low-energy effective evolution; Real clocks; Conclusions.