Internal rotation symmetry of two real scalar fields
= Internal rotation symmetry of two real scalar fields
= Scalar doublet rotation symmetry
{synonym}
For two free <real scalar fields>, the internal rotation $\delta\phi_1=\theta\phi_2$, $\delta\phi_2=-\theta\phi_1$ is a symmetry precisely when their squared masses agree. Its <Noether current> is $j^\mu=\phi_2\partial^\mu\phi_1-\phi_1\partial^\mu\phi_2$. Without mass degeneracy, $\partial_\mu j^\mu=(m_2^2-m_1^2)\phi_1\phi_2$.