Centre vortices in thermal lattice QCD with dynamical fermions

Evidence for a second finite-temperature transition in Quantum Chromodynamics (QCD) is re- vealed through the study of centre vortex geometry and its temperature-dependent evolution. Using the anisotropic dynamical ensembles from the Fastsum collaboration, we conduct a detailed anal- ysis at several temperatures above and below the established chiral transition. Visualisations of the centre vortex structure in temporal and spatial lattice slices demonstrate that vortex percola- tion persists through the chiral transition and ceases at approximately twice the chiral transition temperature, $𝑇_𝑐$ . This indicates that confinement is maintained up to $𝑇 ≈ 2𝑇_𝑐$ , suggesting a second transition associated with deconfinement. The loss of percolation, quantified by vortex cluster extent, provides a clear signal for this transition. Statistical analysis of vortex density and cluster extent is presented which reveals consistent evidence of two transitions in QCD: the chiral transi- tion at $𝑇_𝑐$ and the deconfinement transition at $𝑇_𝑑 ≈ 2𝑇_𝑐$ . By analysing these, and other quantities, we obtain a precise determination of the deconfinement temperature, $𝑇_𝑑$ = 321(6) MeV.