Rudolf Haag's legacy of Local Quantum Physics and reminiscences about a cherished teacher and friend

TL;DR

This paper reflects on Rudolf Haag's influential ideas in Local Quantum Physics, highlighting his contributions to scattering theory, modular operator theory, and the development of string-local fields for higher spin gauge theories.

Contribution

It reviews Haag's foundational work and introduces ongoing research on string-local fields and a new renormalization approach within Local Quantum Physics.

Findings

Insights into Haag's impact on quantum causal localization

Introduction of string-local fields for higher spin theories

Progress towards a reformulation of gauge theory

Abstract

After some personal recollectioms about Rudolf Haag and his thoughts which led him to "Local Quantum Physics", the present work recalls his ideas about scattering theory, the relation between local observables and localized fields and his contributions to the physical aspects of modular operator theory which paved the way for an intrisic understanding of quantum causal localization in which fields "coordinatize" the local algebras. The paper ends with the presentation of string-local fields whose construction and use in a new renormalization theory for higher spin fields is part of an ongoing reformulation of gauge theory in the conceptual setting of Haag's LQP.