NT Seminar - Tyler Gorda, The Ohio State University

Speaker: Tyler Gorda, The Ohio State University

Title: Phase-quenched QCD: A new approach to determine the thermodynamics of deconfined matter to high accuracy

Abstract: The pressure of strongly interacting matter governs the thermodynamics of systems ultimately composed of quarks and gluons. At high temperatures and low net baryon densities, the pressure can be computed directly from the QCD partition function using Monte Carlo lattice methods and compared with experimental determinations. At low temperatures and high densities, however, these techniques fail due to the sign problem, requiring alternative approaches to determine the pressure for phenomena relevant to heavy‑ion collisions at lower center of mass energies and neutron‑star mergers.

In this talk, I present a new method for determining the pressure at high temperatures and/or net baryon densities using simulations of phase‑quenched lattice QCD. This theory is free of the sign problem and provides a strict upper bound on the true QCD pressure at the same quark chemical potentials. Crucially, in the regime where the strong coupling αs is small, phase‑quenched QCD differs from full QCD only at O(αs^3). Using a state‑of‑the‑art diagrammatic technique called hot and dense Loop-Tree Duality, this leading‑order difference can already be computed, enabling a determination of the QCD pressure across a broad region of the phase diagram with an error of O(αs^4), while incorporating nonperturbative pure‑glue contributions from the lattice.