# Decorrelating the topology in full QCD

## TL;DR

This paper examines the challenges of decorrelating topological charge in full QCD simulations using hybrid Monte Carlo and explores simulated tempering as a potential solution.

## Contribution

It highlights the limitations of hybrid Monte Carlo in updating topological structures and investigates simulated tempering to improve decorrelation.

## Key findings

- Hybrid Monte Carlo struggles with topological charge decorrelation.
- Simulated tempering can potentially accelerate topological decorrelation.
- The issue persists regardless of fermion type or number.

## Abstract

We investigate the performance of the hybrid Monte Carlo algorithm in updating non-trivial global topological structures. We find that the hybrid Monte Carlo algorithm has serious problems decorrelating the global topological charge. This represents a warning which must be seriously considered when simulating full QCD, regardless of the number and type of fermions, with this or any similar algorithm. Simulated tempering is examined as a means of accelerating the decorrelation.