We show how to compute electromagnetic polarizabilities of charged hadrons without the use of background fields in lattice QCD.
The low-energy behavior of the Compton scattering amplitude is matched to matrix elements of current-current correlation functions on the lattice. Working in momentum space, formulas for electric polarizability ($\alpha_E$) and magnetic polarizability ($\beta_M$) are derived for both a charged pion and the proton.
Lattice four-point correlation functions are constructed from quark and gluon fields to be used in Monte-Carlo simulations. We also draw attention to the potential of four-point functions as a multi-purpose tool for hadron structure.