Recent results on the running coupling in QCD with two massless flavours

TL;DR

This paper presents updated lattice QCD results on the running coupling using the Schrödinger functional scheme, confirming previous findings and addressing algorithmic challenges like metastable states.

Contribution

It provides new lattice simulation data for the step scaling function in two-flavor QCD and introduces a modified sampling method to handle metastable states.

Findings

Results confirm earlier lattice data on the running coupling.

A modified sampling method improves estimation of metastable states.

Simulations on larger lattices enhance the accuracy of the step scaling function.

Abstract

We report on the latest results on the running coupling of two flavour QCD in the Schr\"odinger functional scheme. Results for the step scaling function are obtained from simulations on lattices $L/a=8$ and $L/a=16$ which confirm the first results from lattices $L/a=4,5,6$ presented one year ago by the ALPHA collaboration. We also discuss some algorithmic aspects, in particular concerning the occurrence of metastable states. A modified sampling, in order to estimate the proper weight of these states in the path integral, is proposed and tested.