Kaons on the lattice

I review recent lattice results in kaon physics, particularly in the determination of Vus and the BK parameter of K0-K̄0 mixing. I use lattice data to argue for the need of developing SU(2)L×SU(2)R chiral perturbation theory for kaon physics and discuss some recent progress in achieving this. In particular it is shown that for K`3 decays at q2 = 0 (where q is the momentum transfer between the kaon and the pion), the chiral logarithms can be calculated in spite of the fact that the external pion carries half the energy of the kaon (in the kaon’s rest frame), because these logarithms arise from soft internal loops. Future prospects, including applications to K → ππ decays are discussed. The need to define and exploit renormalization schemes which can simultaneously be implemented numerically in lattice simulations and used in higher-order perturbative calculations is explained.