Model independent sum rules for B-> pi K decays

We provide a set of sum rules relating CP-averaged branching ratios and CP-asymmetries of the $B \to \pi K$ modes. They prove to be useful as a mechanism to `test' experimental data given our expectations of the size of isospin breaking. A set of observables emerges providing a simpler interpretation of data in terms of isospin breaking. Moreover, the derivation is done in a completely model independent way, i.e., they can accommodate also New Physics contributions.