nonnegative 2 x 2-matrix-valued Hamiltonian (H). I n the literature dealing with the operator
theory of such equations, it is often required in addition that the Hamiltonian H is trace-
normed, ie, satisfies tr (x)≡ 1. Ho wever, in many examples this property does not hold. The
general idea is that one can reduce to the trace-normed case by applying a suitable change
of scale (reparametrization). In this paper we justify this idea and work out the notion of …