Landau singularity and the instability of vacuum state in QED

TL;DR

This paper investigates the foundational issues of Landau singularity and vacuum instability in QED, analyzing their implications for the theory's consistency and the stability of its perturbative vacuum state.

Contribution

It provides a detailed analysis of the Landau singularity and the instability of the QED vacuum, addressing longstanding theoretical problems in quantum electrodynamics.

Findings

Landau singularity indicates a pole in the effective coupling at high energy.

Perturbative vacuum in QED may be unstable due to these singularities.

The paper discusses the implications for the consistency of QED as a fundamental theory.

Abstract

Quantum Eletrodynamics (QED) is considered as the most successful of all physical theories. It can predict numerical values of physical quantities to a spectacular degree of accuracy. However, from the very early days it has been known that, in QED, there are two important problems which are linked with the very foundation of the theory. In 1952, Dyson put forward strong argumnts to suggest that the perturbation seires in quantum electrodynamics can not be convergent. Just three years latter, in 1955, Landau argued that the effective running coupling constant in QED has a pole (Landau singularity) albeit at some very high energy scale. This paper addresses, in details, the question of stability of perturbative vacuum state of QED in the light of these two well known problems. Landau has been a cult-like figure for many of us who studied theoretical physics in the former Soviet Union. As an undergraduate student in the department of theoretical physics of People's Friendship University, Moscow, in 1970's, I grew up hearing colourful stories about the legendary persona of Lev Davidovich from my teachers some of whom had known him at personal level. It is a great honour for me to contribute this article to the Landau centenary volume of "Eletronics Journal of Theoretical Physics".