Density Matrix Renormalisation Group Approach to the Massive Schwinger Model

TL;DR

This paper applies a density matrix renormalisation group method to the massive Schwinger model, achieving highly accurate continuum limit estimates and confirming theoretical predictions about phase transitions and particle behavior.

Contribution

It introduces a DMRG approach to the lattice Hamiltonian of the massive Schwinger model, significantly improving accuracy over previous methods.

Findings

Confirmed Coleman's half-asymptotic particles at theta=pi

Located the phase transition at finite fermion mass accurately

Demonstrated the transition belongs to the 2D Ising universality class

Abstract

The massive Schwinger model is studied, using a density matrix renormalisation group approach to the staggered lattice Hamiltonian version of the model. Lattice sizes up to 256 sites are calculated, and the estimates in the continuum limit are almost two orders of magnitude more accurate than previous calculations. Coleman's picture of `half-asymptotic' particles at background field theta = pi is confirmed. The predicted phase transition at finite fermion mass (m/g) is accurately located, and demonstrated to belong in the 2D Ising universality class.