# Lower bound of the spectrum of a Schrodinger operator on a bounded domain

I am trying to look for references on estimate of the lower bound of the spectrum of a Schrodinger operator $-\Delta + V$ on a bounded domain in three-dimensional space. For simplicity, we can take the domain to be a ball or torus, and the potential $V$ to be cylindrically radial, i.e. $V = V(r)$, where $r$ is as in the cylindrical coordinates.

Any suggestion is welcome - Thanks in advance!