The Neutron Electric Dipole Moment in the Instanton Vacuum: Quenched Versus Unquenched Simulations

Abstract

We investigate the role played by the fermionic determinant in the evaluation of the CP-violating neutron electric dipole moment (EDM) adopting the Instanton Liquid Model. Significant differences between quenched and unquenched calculations are found. In the case of unquenched simulations the neutron EDM decreases linearly with the quark mass and is expected to vanish in the chiral limit. On the contrary, within the quenched approximation, the neutron EDM increases as the quark mass decreases and is expected to diverge as (1/m)**Nf in the chiral limit. We argue that such a qualitatively different behavior is a parameter-free, semi-classical prediction and occurs because the neutron EDM is sensitive to the topological structure of the vacuum. The present analysis suggests that quenched and unquenched lattice QCD simulations of the neutron EDM as well as of other observables governed by topology might show up important differences in the quark mass dependence, for mq < Lambda(QCD).

arXiv comment8 pages, 3 figures, 2 tables

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Cited by in corpus (11)

• Theta dependence of SU(N) gauge theories in the presence of a topological term
• Calculation of the neutron electric dipole moment with two dynamical flavors of domain wall fermions
• Neutron electric dipole moment with external electric field method in lattice QCD
• Neutron electric dipole moment using $N_f=2+1+1$ twisted mass fermions
• Neutron electric dipole moment using lattice QCD simulations at the physical point
• Chiral perturbation theory in a theta vacuum
• Neutron electric dipole moment from lattice QCD
• Strong CP breaking and quark-antiquark repulsion in QCD, at finite theta
• Computing the Effective Hamiltonian of Low-Energy Vacuum Gauge Fields
• The topological susceptibility from grand canonical simulations in the interacting instanton liquid model: zero temperature calibrations and numerical framework
• Nucleon matrix element of Weinberg's CP-odd gluon operator from the instanton vacuum