Traversable wormholes: the Roman ring

TL;DR

This paper introduces a novel class of geometries called 'Roman rings' of traversable wormholes, which challenge the reliability of semi-classical chronology protection theorems by showing that quantum effects can be minimized near the threshold of chronology violation.

Contribution

It proposes the 'Roman ring' configuration of wormholes, demonstrating that quantum vacuum polarization can be made arbitrarily small, questioning the reliability of semi-classical chronology protection.

Findings

Quantum vacuum polarization can be minimized in Roman rings.

Back-reaction remains small up to the reliability horizon.

Semi-classical gravity may become unreliable before large back-reaction occurs.

Abstract

In this brief report I introduce a yet another class of geometries for which semi-classical chronology protection theorems are of dubious physical reliability. I consider a ``Roman ring'' of traversable wormholes, wherein a number of wormholes are arranged in a ring in such a manner that no subset of wormholes is near to chronology violation, though the combined system can be arbitrarily close to chronology violation. I show that (with enough wormholes in the ring) the gravitational vacuum polarization (the expectation value of the quantum stress-energy tensor) can be made arbitrarily small. In particular the back-reaction can be kept arbitrarily small all the way to the ``reliability horizon''---so that semi-classical quantum gravity becomes unreliable before the gravitational back reaction becomes large.