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Quantum Monte Carlo (QMC) methods, when applicable, offer dependable ways to extract the nonperturbative physics of strongly-correlated many-body systems. However, there are some formidable bottlenecks to the applicability of these methods such as the sign problem and algorithmic update inefficiencies. Using the t-V model Hamiltonian, I demonstrate how the fermion bag approach--originally developed in the context of Lagrangian lattice field theories--led to the first sign problem solution for this model. I then show how using fermion bag ideas to develop a new efficient QMC algorithm to study the t-V model allowed us to compute critical exponents for the chiral Ising universality class (involving one flavor of four-component Dirac fermions) that seem to be more reliable than those from previous QMC calculations. Finally, I discuss how the fermion bag approach offers certain advantages to the study of other models involving Dirac fermions and also extends to fermion-spin interactions and Z_2 gauge theories.

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Emilie Huffman, Uni Wuerzburg
Seminar Room 0.03, ETP
Contact: Michael Scherer