Multipion states in lattice QCD and the charged-pion condensate

Abstract

The ground-state energies of systems containing up to 12 pi(+)'s in a spatial volume V similar to(2.5 fm)(3) are computed in dynamical, mixed-action lattice QCD at a lattice spacing of similar to 0.125 fm for four different values of the light-quark masses. Clean signals are seen for each ground-state, allowing for a precise extraction of both the pi(+)pi(+) scattering length and pi(+)pi(+)pi(+) interaction from a correlated analysis of systems containing different numbers of pi(+)'s. This extraction of the pi(+)pi(+) scattering length is consistent with that from the pi(+)pi(+) system alone. The large number of systems studied here significantly strengthens the arguments presented in our earlier work and unambiguously demonstrates the presence of a low energy pi(+)pi(+)pi(+) interaction. The equation of state of a pi(+) gas is investigated using our numerical results and the density dependence of the isospin chemical potential for these systems agrees well with the theoretical expectations of leading order chiral perturbation theory. The chemical potential is found to receive a substantial contribution from the pi(+)pi(+)pi(+) interaction at the lighter pion masses. An important technical aspect of this work is the demonstration of the necessity of performing propagator contractions in greater than double precision to extract the correct results.

Department

Physics

Publication Date

7-18-2008

Journal Title

Physical Review D

Publisher

AMERICAN PHYSICAL SOCIETY

Digital Object Identifier (DOI)

10.1103/PhysRevD.78.014507

Document Type

Article

Rights

© 2008 The American Physical Society

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