Bulk viscosity in kaon condensed matter

We investigate the effect of K{sup -} condensed matter on bulk viscosity and r-mode instability in neutron stars. The bulk viscosity coefficient due to the nonleptonic process n p+K{sup -} is studied here. In this connection, equations of state are constructed within the framework of relativistic field theoretical models where nucleon-nucleon and kaon-nucleon interactions are mediated by the exchange of scalar and vector mesons. We find that the bulk viscosity coefficient due to the nonleptonic weak process in the condensate is suppressed by several orders of magnitude. Consequently, kaon bulk viscosity may not damp the r-mode instability in neutron stars.