Fermion Discretization Effects in the Two-Flavor Lattice Schwinger Model: A Study with Matrix Product States

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Hauptverfasser: Schwägerl, Tim, Jansen, Karl, Kühn, Stefan
Format: Preprint
Veröffentlicht: 2025
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author Schwägerl, Tim
Jansen, Karl
Kühn, Stefan
author_facet Schwägerl, Tim
Jansen, Karl
Kühn, Stefan
contents We present a comprehensive tensor network study of staggered, Wilson, and twisted mass fermions in the Hamiltonian formulation, using the massive two-flavor Schwinger model as a benchmark. Particular emphasis is placed on twisted mass fermions, whose properties in this context have not been systematically explored before. We confirm the expected O(a) improvement in the free theory and observe that this improvement persists in the interacting case. By leveraging an electric-field-based method for mass renormalization, we reliably tune to maximal twist and establish the method's applicability in the two-flavor model. Once mass renormalization is included, the pion mass exhibits rapid convergence to the continuum limit. Finite-volume effects are addressed using two complementary approaches: dispersion relation fits and finite-volume scaling. Our results show excellent agreement with semiclassical predictions and reveal a milder volume dependence for twisted mass fermions compared to staggered and Wilson discretizations. In addition, we observe clear isospin-breaking effects, suggesting intriguing parallels with lattice QCD. These findings highlight the advantages of twisted mass fermions for Hamiltonian simulations and motivate their further exploration, particularly in view of future applications to higher-dimensional lattice gauge theories.
format Preprint
id arxiv_https___arxiv_org_abs_2509_02329
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Fermion Discretization Effects in the Two-Flavor Lattice Schwinger Model: A Study with Matrix Product States
Schwägerl, Tim
Jansen, Karl
Kühn, Stefan
High Energy Physics - Lattice
We present a comprehensive tensor network study of staggered, Wilson, and twisted mass fermions in the Hamiltonian formulation, using the massive two-flavor Schwinger model as a benchmark. Particular emphasis is placed on twisted mass fermions, whose properties in this context have not been systematically explored before. We confirm the expected O(a) improvement in the free theory and observe that this improvement persists in the interacting case. By leveraging an electric-field-based method for mass renormalization, we reliably tune to maximal twist and establish the method's applicability in the two-flavor model. Once mass renormalization is included, the pion mass exhibits rapid convergence to the continuum limit. Finite-volume effects are addressed using two complementary approaches: dispersion relation fits and finite-volume scaling. Our results show excellent agreement with semiclassical predictions and reveal a milder volume dependence for twisted mass fermions compared to staggered and Wilson discretizations. In addition, we observe clear isospin-breaking effects, suggesting intriguing parallels with lattice QCD. These findings highlight the advantages of twisted mass fermions for Hamiltonian simulations and motivate their further exploration, particularly in view of future applications to higher-dimensional lattice gauge theories.
title Fermion Discretization Effects in the Two-Flavor Lattice Schwinger Model: A Study with Matrix Product States
topic High Energy Physics - Lattice
url https://arxiv.org/abs/2509.02329