Mesons upon low-lying Dirac mode exclusion

TL;DR

This study investigates the effects of removing low-lying Dirac eigenmodes on meson properties in lattice QCD, revealing symmetry restorations and degeneracies among meson states.

Contribution

It demonstrates that excluding low-lying Dirac modes leads to symmetry restoration and degeneracy among mesons, providing insights into the underlying QCD dynamics.

Findings

Disconnected contributions vanish after mode subtraction

All J=0 correlators become identical, indicating symmetry restoration

J=1 states become degenerate, showing SU(4) symmetry

Abstract

We study the isoscalar and isovector $J=0,1$ mesons with the overlap operator within two flavour lattice QCD. After subtraction of the lowest-lying Dirac eigenmodes from the valence quark propagator all disconnected contributions vanish and all possible point-to-point $J=0$ correlators become identical, signaling a simultaneous restoration of both $SU(2)_L \times SU(2)_R$ and $U(1)_A$ symmetries. The ground states of the $\pi,\sigma,a_0,\eta$ mesons do not survive this truncation. All possible $J=1$ states have a very clean exponential decay and become degenerate, demonstrating a $SU(4)$ symmetry of a dynamical QCD-like string.