How important is $i\epsilon$ in QFT?

TL;DR

This paper explores the role of the $i\,\epsilon$ term in quantum field theory, proposing it can be equated with the dimensional regularization parameter to clarify infrared divergence issues.

Contribution

It introduces a novel interpretation of $i\epsilon$ as the dimensional regularization parameter, simplifying the understanding of infrared divergences in QFT.

Findings

Identifies $i\epsilon$ with the dimensional regularization parameter $4-d$.

Clarifies the role of $i\epsilon$ in the optical theorem.

Simplifies the treatment of infrared divergences.

Abstract

We discuss the role of $i\epsilon$ in quantum field theories and suggest that it can be identified with the dimensional regularization parameter $i\epsilon=4-d$ thus clarifying and simplifying issues related to the infrared divergences without altering any of the present knowledge in QFT. We further present the relevance of this assumption for the optical theorem.