The strong couplings of massive Yang-Mills theory

Understand

We study the massive Yang-Mills theory in which the mass term is added by hand.

• The standard perturbative approach suggests that the massless limit of this theory is not smooth.
• We confirm that this issue is related to the existence of additional degrees of freedom, which are absent in the massless theory.
• Nevertheless, we show that the longitudinal modes become strongly coupled at the Vainshtein scale, which coincides with the scale of the unitarity violation.