Individual eigenvalue distributions for chGSE-chGUE crossover and determination of low-energy constants in two-color QCD+QED

TL;DR

This paper analyzes the distributions of low-lying eigenvalues in random matrix models interpolating between chGSE and chGUE, applying these results to determine low-energy constants in two-color QCD+QED through lattice simulations.

Contribution

It introduces a method to compute eigenvalue distributions using Fredholm Pfaffians and applies this to extract physical constants from lattice gauge theory data.

Findings

Eigenvalue distributions are accurately modeled by the interpolating ensembles.

Precise determination of the pseudo-scalar decay constant F from lattice data.

The U(1) coupling dependence of related physical quantities is characterized.

Abstract

We compute statistical distributions of individual low-lying eigenvalues of random matrix ensembles interpolating chiral Gaussian symplectic and unitary ensembles. To this aim we use the Nystrom-type discretization of Fredholm Pfaffians and resolvents of the dynamical Bessel kernel containing a single crossover parameter \rho. The \rho-dependent distributions of the four smallest eigenvalues are then used to fit the Dirac spectra of modulated SU(2) lattice gauge theory, in which the reality of the staggered SU(2) Dirac operator is weakly violated either by the U(1) gauge field or by a constant background flux. Combined use of individual eigenvalue distributions is effective in reducing statistical errors in \rho; its linear dependence on the imaginary chemical potential \mu_I enables precise determination of the pseudo-scalar decay constant F of the SU(2) gauge theory from a small lattice. The U(1)-coupling dependence of an equivalent of F^2 \mu_I^2 in the SU(2) x U(1) theory is also obtained.