Fluctuation-induced Nambu–Goldstone bosons in a Higgs–Josephson model

We present a new mechanism of fluctuation-induced Nambu–Goldstone bosons in a scalar field theory of Higgs–Josephson systems. We consider a simple scalar field model with $U{{(1)}^{n}}$ rotational symmetry. When there is an interaction which violates the rotational symmetry, the Nambu–Goldstone bosons become massive and massless bosons are concealed. We present a model where the massive boson becomes a massless boson as a result of the perturbative fluctuation. In our model the ${{{\bf Z}}_{2}}$ -symmetry associated with the chirality is also broken. The transition occurs as a first-order transition at the critical point. The ground state at absolute zero will flow into the state with more massless bosons due to fluctuation effects at finite temperature.