Speaker: Saga Säppi

Title: QCD at finite density with high-order perturbation theory

Abstract: With significant recent advances in both observations of quiescent neutron stars as well as LIGO and its friends kicking off the advent of gravitational wave astronomy, understanding the physics of neutron stars has become increasingly important. From the point of view of particle physics, this means understanding the physics of Quantum Chromodynamics at finite baryon density. As lattice simulations fail in the relevant regime due to a sign problem, perturbative QCD is one of the only first-principles methods of studying matter at extremely high densities.

I will start by setting up the formalism of thermal field theories, including a discussion on the Hard Thermal Loop effective theories for treating the low-energy degrees of freedom. Using it, I will go over recent advances in computing the equation of state to next-to-next-to-next-to-leading order by means of an improved understanding of HTLs, and finish by discussing a recent computation of the bulk viscosity of deconfined quark matter.

This talk will be in hybrid mode via zoom, please contact the seminar organisers to obtain the password.

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