Logarithmic Corrections in Quantum Impurity Problems

TL;DR

This paper investigates how a bulk marginal operator influences boundary critical phenomena in 2D quantum systems, specifically analyzing an S=1/2 antiferromagnetic Heisenberg chain, revealing logarithmic corrections relevant to experiments.

Contribution

It provides an exact solution for boundary critical phenomena in a 2D quantum model considering a bulk marginal operator, introducing a novel operator product expansion with three operators.

Findings

Logarithmic corrections in finite size calculations

Logarithmic corrections in NMR experiments

New operator product expansion involving three operators

Abstract

The effect of a BULK marginal operator on BOUNDARY critical phenomena in two space-time dimensions is considered. The particular case of an open S=1/2 antiferromagnetic Heisenberg chain, corresponding to a Wess-Zumino-Witten non-linear sigma model, is solved. In this case, the needed renormalization group coefficient is associated with a novel operator product expansion in which THREE operators approach the same point. Resulting logarithmic corrections occurring in finite size calculations and nuclear magnetic resonance experiments are discussed.