Composite massless vector boson

Abstract

In a nonperturbative gauge-invariant formulation of grand unified theories all low-energy vector states need to be composite with respect to the high-scale gauge group, including the photon. We investigate this by using lattice methods to spectroscopically analyze the vector channel in a toy grand unified theory: an SU(2) adjoint Higgs model. Our results indeed support the existence of a massless composite vector particle.