Theta vacuum effects on the chiral condensation and the eta^prime meson correlators in the two-flavor massive QED_2 on the lattice

TL;DR

This study investigates how the theta vacuum influences chiral condensates and eta' meson correlators in the two-flavor massive Schwinger model, revealing non-zero pseudoscalar condensation and long-range eta' correlations.

Contribution

The paper introduces a new method to analyze topological effects in the Schwinger model, demonstrating the impact of theta vacuum on meson correlators and condensates.

Findings

Pseudoscalar condensation is non-zero in non-zero theta vacuum.

Long-range correlation of eta' meson exists due to topological effects.

Cancellation of correlations at theta=0 involves higher topological sectors.

Abstract

We study the scalar and pseudoscalar condensations and the eta^prime meson correlators of the two-flavor massive Schwinger model in the non-zero theta vacuum. Exploiting our new method which was developed to investigate topological effects in the previous work, we find that the pseudoscalar condensation is non-zero and there exists a long-range correlation of the eta^prime meson. This phenomenon is well described by the clustering property. We also find that even in theta=0 case the cancellation of the long-range correlation is nontrivial and requires accurate contributions from higher topological sectors. Our results imply that the fluctuation of the ``disconnected'' diagram originates from the pseudoscalar condensation in each topological sector.