I-spin, U-spin, and penguin dominance in B→KKK

Isospin and U-spin symmetries are useful approximations for studying penguin dominance in B meson decays to three kaons, B→KKK. We point out certain subtleties in treating these decays in these approximations. Resulting uncertainties are discussed in determining the CP content of the final state in B→K+K−KS, and in relating the CP asymmetry in this process to the value of sin2β.