Fermion bag approach to Hamiltonian lattice field theories in continuous time

TL;DR

This paper introduces a fermion bag approach for Hamiltonian lattice field theories in continuous time, enabling efficient quantum Monte Carlo simulations and accurate critical exponent calculations in the 3d Ising Gross-Neveu class.

Contribution

The paper develops a continuous time fermion bag method and a quantum Monte Carlo algorithm for Hamiltonian lattice models, providing a new tool for studying critical phenomena.

Findings

Calculated critical exponents η=0.54(6) and ν=0.88(2) for the 3d Ising Gross-Neveu class.

Demonstrated the feasibility of simulating up to 10,000 sites with current supercomputers.

Proposed that the temperature parameter helps identify fermion bags in continuous time models.

Abstract

We extend the idea of fermion bags to Hamiltonian lattice field theories in the continuous time formulation. Using a class of models we argue that the temperature is a parameter that splits the fermion dynamics into small spatial regions that can be used to identify fermion bags. Using this idea we construct a continuous time quantum Monte Carlo algorithm and compute critical exponents in the 3d Ising Gross-Neveu universality class using a single flavor of massless Hamiltonian staggered fermions. We find $\eta$=0.54(6) and $\nu$=0.88(2) using lattices up to N=2304 sites. We argue that even sizes up to N=10,000 sites should be accessible with supercomputers available today.