Recent advances in perturbative QCD at high density

TL;DR

The work addresses how to obtain reliable microphysical input for neutron-star matter at high density using perturbative QCD. It centers on extending the Loop Tree Duality approach to thermal settings to render high-loop calculations tractable as convergent multidimensional integrals, enabling a complete N3LO pressure for cold, dense QM. It also discusses bulk viscosity calculations up to N2LO and the role of electroweak rates and pairing in shaping transport properties. These advances sharpen model-independent inferences of the neutron-star matter equation of state and open avenues for finite-temperature extensions and Beyond-the-Standard-Model tests in high-density QCD.

Abstract

In these conference proceedings, we discuss recent progress in high-order perturbative studies of the thermodynamic and transport properties of dense quark matter. Special emphasis is placed on the introduction of a promising new computational tool, thermal Loop Tree Duality, which enables pushing the existing weak-coupling calculations to higher perturbative orders.

Figures (2)

• Figure 1: Left: the NLO, N2LO and N3LO pressures of cold and dense QM Gorda:2023mkk, with the one unknown coefficient $c_0$ set to a value suggested by Bayesian arguments. Right: the model-independent pressure of cold beta-equilibrated NS matter as a function of baryon chemical potential Annala:2023cwx, with the high-density pQCD constraint visible as the violet band on the right (see original paper for details).
• Figure 2: The non-leptonic contributions to the LO, NLO, and N2LO bulk viscosity of unpaired QM, taken from the recent CruzRojas:2024etx.