KAON ZERO-POINT FLUCTUATIONS IN NEUTRON-STAR MATTER

We investigate the contribution of zero-point motion, arising from flu ctuations in kaon modes, to the ground state properties of neutron sta r matter containing a Bose condensate of kaons. The zero-point energy is derived via the thermodynamic partition function, by integrating ou t fluctuations for an arbitrary value of the condensate field. It is s hown that the vacuum counterterms of the chiral Lagrangian ensure the cancellation of divergences dependent on mu, the charge chemical poten tial, which may be regarded as an external vector potential. The total grand potential, consisting of the tree-level potential, the zero-poi nt contribution, and the counterterm potential, is extremized to yield a locally charge neutral, beta-equilibrated and minimum energy ground state. In some regions of parameter space we encounter the well-known problem of a complex effective potential. Where the potential is real and solutions can be obtained, the contributions from fluctuations ar e found to be small in comparison with tree-level contributions.