Scalar mass matrix
= Scalar mass matrix
{title2=$M^2_{ij}=\partial_i\partial_jV$}
The scalar mass matrix is the <Hessian matrix> of the <scalar potential> at a vacuum. Its eigenvalues are the tree-level squared masses; broken symmetry directions are zero eigenvectors before a <Higgs mechanism> or explicit symmetry breaking removes the corresponding massless modes.