Photon-photon scattering: a tutorial

Understand

Long-established results for the low-energy photon-photon scattering, gamma gamma --> gamma gamma, have recently been questioned.

• We analyze that claim and demonstrate that it is inconsistent with experience.
• We demonstrate that the mistake originates from an erroneous manipulation of divergent integrals and discuss the connection with another recent claim about the Higgs decay into two photons.
• We show a simple way of correctly computing the low-energy gamma gamma scattering.