Solution
= Solution
If $\mu^2,\lambda^2>0$, the unique ground state is $\boldsymbol\phi_0=0$. The full $O(1)\times O(2)$ symmetry remains unbroken and every mode is gapped.
= Solution
If $\mu^2,\lambda^2>0$, the unique ground state is $\boldsymbol\phi_0=0$. The full $O(1)\times O(2)$ symmetry remains unbroken and every mode is gapped.