# Open-Boundary Conditions in the Deconfined Phase

## TL;DR

This paper investigates open-boundary conditions at high temperatures to measure boundary effects, screening masses, and topological susceptibility in lattice gauge theories, revealing temperature-dependent boundary zone sizes and challenges due to topological freezing.

## Contribution

It introduces the use of open-boundary conditions at high temperatures to study boundary effects and topological susceptibility, providing new measurements and insights into temperature-dependent phenomena.

## Key findings

- Boundary effects are larger at T=1.5T_c than at T=0, smaller at T=2.7T_c.
- Scalar and pseudo-scalar screening masses are measured, showing a mass gap at T=1.5T_c but not at T=2.7T_c.
- Topological susceptibility estimates are consistent with literature at T=1.5T_c but limited at T=2.7T_c due to topological freezing.

## Abstract

In this work, we consider open-boundary conditions at high temperatures, as they can potentially be of help to measure the topological susceptibility. In particular, we measure the extent of the boundary effects at $T=1.5T_c$ and $T=2.7T_c$. In the first case, it is larger than at $T=0$ while we find it to be smaller in the second case. The length of this "boundary zone" is controlled by the screening masses. We use this fact to measure the scalar and pseudo-scalar screening masses at these two temperatures. We observe a mass gap at $T=1.5T_c$ but not at $T=2.7T_c$. Finally, we use our pseudo-scalar channel analysis to estimate the topological susceptibility. The results at $T=1.5T_c$ are in good agreement with the literature. At $T=2.7T_c$, they appear to suffer from topological freezing, impeding us from providing a precise determination of the topological susceptibility. It still provides us with a lower bound, which is already in mild tension with some of the existing results.