In the present paper we study the limit of zero mass in nonabelian gauge
theories both with Higgs mechanism and in the nonlinear realization of the
gauge group (Stueckelberg mass). We argue that in the first case the
longitudinal modes undergo a metamorphosis process to the Goldstone scalar
modes, while in the second we guess a decoupling process associated to a phase
transformation. The two scenarios yield strikingly different behaviors at high
energy, mainly ascribed to the presence of a massless Higgs doublet among the
physical modes in the case of Higgs mechanism (i.e. not only the Higgs boson).
The aim of this work is to show that the problem of unitarity at high energy in
nonabelian gauge theory with no Higgs boson can open new perspectives in
quantum field theory.Comment: Article, 31 pages. Typos removed and Ref. 7, 32 added. Revised
argument in sections 4,9,10, results unchange
