Non-analyticity of the $S$-matrix with spontaneously broken Lorentz invariance

Paolo Creminelli, Matteo Delladio, Oliver Janssen +2

We study the $S$-matrix of Goldstones in the renormalizable theory of a $U(1)$ complex scalar at finite charge, i.e. in a state that breaks Lorentz invariance. The theory is weakly…