Speaker
Description
We study the 2-d $U(1)$ gauge Higgs model with 2 flavors on the lattice. We simulate at topological angle $\theta=\pi$ and overcome the sign problem with a worldline representation of the theory. Using a novel definition of the theta-term, in terms of a Villain-type action, gives rise to a lattice discretization of the topological charge as an integer and thus, exactly implements the charge conjugation symmetry at $\theta=\pi$.
We introduce a new coupling $g$ in the 2-flavor quartic self interaction that allows us to deform the full $SU(2)$ flavor symmetry to $\mathbb{Z}_2 \times U(1)$. We study the phase diagram of this system as a function of $g$ and the mass parameter and determine the critical lines as well as the order of the phase transitions using finite size scaling.
