Isaac Hailperin : May 15, 2008

Eigenvalue spectrum of twisted mass lattice QCD.

Abstract

The eigenvalue spectrum of the twisted mass lattice QCD Dirac operator is investigated. As this is a large matrix, it is important to use an efficient eigensolver here. We compare the performance of the Lanczos and the Jacobi-Davidson algorithms. The low-lying eigenvalues for various ensembles of gauge configurations are computed. We use the twisted mass formulation of lattice QCD, which has the advantage of introducing lattice artifacts only of order a2, at the expense of tuning only on parameter. We observe the O(a2) dependence in the eigenvalue spectrum. Investigating finite volume effects, it turns out that the largest lattices that we use are sufficient to approximate the infinite volume limit.