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**UNC-CH Physics and Astronomy Colloquium**

Gökce Basar, University of Illinois, Chicago

**“Going with the flow: making the path integral more complex”**

The theory of strong interactions (Quantum Chromo Dynamics, or QCD), which describes how the constituents of protons and neutrons (quarks and gluons) interact, has been around for more than 40 years. However, the calculation of the properties of nuclear matter in various phases from QCD remains an unsolved problem. These phases include quark gluon plasma, the phase that filled the universe microseconds after it was formed, and dense nuclear matter, which exists in the cores of compact stars. The reason these calculations remain elusive is an infamous obstacle called the ‘sign problem.’ In this talk, I explore a new way of tackling the sign problem that involves generalizing the Feynman path integral to complex fields. I discuss both conceptual and computational aspects of this new approach, and give examples of interacting quantum field theories where it successfully solves the sign problem, with the goal of eventually using it to solve QCD.