Renormalization group irreversible functions in more than two dimensions

TL;DR

This paper compares two irreversibility theorems for the renormalization group in higher dimensions, clarifies their conditions, and discusses their universality and applicability limitations.

Contribution

It establishes the validity conditions of the Forte-Latorre theorem, compares it with the entropic theorem, and analyzes their universality and dimensional constraints.

Findings

The Forte-Latorre theorem's irreversibility function is non-universal.

The entropic theorem's irreversibility is universal.

The integral of the stress-tensor trace correlator is finite only in dimensions less than four.

Abstract

There are two general irreversibility theorems for the renormalization group in more than two dimensions: the first one is of entropic nature, while the second one, by Forte and Latorre, relies on the properties of the stress-tensor trace, and has been recently questioned by Osborn and Shore. We start by establishing under what assumptions this second theorem can still be valid. Then it is compared with the entropic theorem and shown to be essentially equivalent. However, since the irreversible function of the (corrected) Forte-Latorre theorem is non universal (whereas the relative entropy of the other theorem is universal), it needs the additional step of renormalization. On the other hand, the irreversibility theorem is only guaranteed to be unambiguous if the integral of the stress-tensor trace correlator is finite, which happens for free theories only in dimension smaller than four.