On the Quantum Stability of the Time Machine

Abstract

One of the most serious attempts to find a mechanism “protecting causality” was made in a number of papers beginning from [1, 2] where it is argued that vacuum fluctuations prevent the creation of a time machine by making the expectation value of the stress-energy tensor 〈T〉^ren diverge at the Cauchy horizon. In the present talk I show that

• 1. There are spacetimes with causality violated and with 〈T〉^ren, nevertheless, bounded in causal regions.

• 2. There is actually no reason to expect that 〈T〉^ren diverges in the general case.