# The 35th International Symposium on Lattice Field Theory

18-24 June 2017
Palacio de Congresos
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Andalucía III

# Variance Reduction via Cluster Decomposition and nEDM with theta Term

## Speakers

• Prof. Keh-Fei LIU

## Content

It is a common problem in In lattice QCD calculations of hadron masses with annihilation channel that the signal falls off in time separation while the noise remains constant. In addition, the disconnected insertion calculation in the three-point function and the calculation of the neutron electric dipole moment (nEDM) with the $\theta$ terms suffer from a noise due to the $\sqrt{V}$ fluctuation. We show that these problems have the same origin and the $\sqrt{V}$ problem can be resolved by utilizing the cluster decomposition principle. We demonstrate this by considering the calculation of glueball mass, the strangeness content in the nucleon, and the CP violation angle in the nucleon due to the $\theta$ term and found that for lattices with a physical sizes of 4.5 - 5.5 fm, the errors of these quantities can be reduced a factor of 3 to 4. We also report calculation of the nEDM from the $\theta$ term with overlap valence on the $24^3 \times 64$ DWF configurations.