Speaker
Description
In this talk a complete unitarity framework for quantum field theories whose massive scalar excitations propagate at different sound speeds will be presented. Starting from first principles we derive the exact partial-wave unitarity condition for «two-to-two» scattering with arbitrary masses and velocity hierarchies, recovering the standard and massless limits as special cases. Applying the formalism to a renormalizable two-field model, the optical theorem at one loop is verified and next we obtain compact, velocity-dependent perturbative unitarity bounds. Then the one-loop Coleman-Weinberg potential is derived in the background-field method, tracking how a small splitting between sound speeds reshapes the renormalization-group flow. Finally, it will be shown that all of quartic β-functions are rescaled in such a way that an accidental fixed line emerges.
