WKB expansion for systems of Schrödinger operators with crossing eigenvalues
Let M be a compact, connected C∞ manifold with a C∞ Riemannian metric or let M=Rn with Euclidean metric. Let g denote the metric. On M consider the 2×2 system of Schrödinger operators[TeX:] \[P=-h^{2}\Delta +V+h^{2}\mathcal{W},\qquadV=\left(\begin{array}[cc]v_{1}&0\\0&v_{2}\end{array}\right)\]where v1,v2∈C∞(M) are non-negative, and W is a C∞, first order formally selfadjoint differential o
