Boris Svistunov (University of Massachusetts, Amherst) 

Diagrammatic Monte Carlo for Fermionic and Fermionized Systems

Under certain (controlled) conditions, Feynman diagrammatic series for fermionic systems features the phenomenon of sign blessing: The series converges despite factorial growth of the number of diagrams with diagram order. Diagrammatic Monte Carlo technique allows us to sample millions of Feynman diagrams. With the universal fermionization trick, we can fermionize essentially any (bosonic, spin, mixed, etc.) lattice system. The combination of fermionization and diagrammatic Monte Carlo yields a universal first-principle approach to strongly correlated lattice systems, provided the sign blessing is a generic fermionic phenomenon. We will present results for resonant fermions, fermionized spins-1/2 on triangular lattice, and repulsive Hubbard model.