Sign Optimization and Quantum Field Theories: Lessons from QCD-like models

Monte Carlo methods using the lattice formulation provide the only known procedure for calculating the predictions of Quantum Chromodynamics (QCD) in the low energy, strongly coupled regime. In the presence of a fermion chemical potential or for systems evolving in time the QCD action becomes complex and these methods break down. While QCD has existed as a theory for half a century, and lattice field theory calculations including the effect of fermions for decades, this sign problem has so far prevented calculation of the phase structure of strongly interacting matter. Recently a new approach, involving complexifying the domain of integration and deforming the path integrals, has been suggested as a way to ameliorate the sign problem. In the sign optimization method a family of complexified integration domains, parameterized by their real parts, is introduced, and an optimal member of this family is selected using gradient descent. This thesis applies sign optimization to 0+1D QCD and Heavy Dense QCD, two models that, while more tractable than QCD, give some insight into how the general thimble method may be applied to the full theory.

Topic: Joseph Marincel doctoral defense

Time: Aug 14, 2023 11:00 AM Eastern Time (US and Canada)

Zoom link: https://unc.zoom.us/j/5670252938