Raymond and instantons: some recollections and the use of ADHM

TL;DR

This paper reflects on the historical development of instantons, discusses the ADHM method for constructing calorons in thermal QCD, and presents simplified results on vacuum response and screening effects.

Contribution

It provides a historical perspective on instantons, details the use of the ADHM method for calorons, and introduces simplified formulas for vacuum response in thermal QCD.

Findings

Simplified expressions for one-loop vacuum response to caloron parameters

Insights into screening properties in thermal QCD

Historical recollections of instanton research in the 1970s

Abstract

After the discovery of the BRST identities in 1974 Raymond spent some two years mostly on instantons. In those years we had a small group at the Centre Physique Th\'eorique in Marseille discussing the physics and mathematics of instantons. The upshot of our discussions can be found in a set of lectures given by Raymond in Erice in 1977 and a year later in a Physics Reports volume. I present some recollections of that period; mostly how we were influenced by the twistor approach. I discuss the Atiyah-Drinfeld-Hitchin-Manin (ADHM) method to obtain instantons ("calorons") in thermal QCD following earlier work. The building blocks are a prepotential and a gauge invariant propagator. Then I will give surprisingly simple results in terms of these building blocks for the one loop vacuum response to a change in caloron parameters and some physical consequences for the effective action, in particular screening properties.