Unstable Systems in Relativistic Quantum Field Theory

TL;DR

This paper defines unstable particle states using stable asymptotic states and addresses longstanding issues related to the decay amplitude's behavior over short and long times.

Contribution

It introduces a general framework for describing unstable particles in relativistic quantum field theory using stable asymptotic states.

Findings

Resolved problems with short-time decay behavior.

Provided a new definition for unstable particle states.

Analyzed large-time decay amplitude behavior.

Abstract

We show how the state of an unstable particle can be defined in terms of stable asymptotic states. This general definition is used to discuss and to solve some old problems connected with the short-time and large-time behaviour of the non-decay amplitude.