On Time-Reversal Equivariant Hermitian Operator Valued Maps from a 2D-Torus Phase Space

Abstract

In this paper we classify maps from a torus phase space $X$ to $\mathcal{H}_n^*$, the space of $n \times n$, non-singular hermitian operators up to equivariant homotopy. The equivariance is with respect to a time-reversal involution on $X$ and an involution on $\mathcal{H}_n^*$ defining a certain symmetry class. Furthermore we study certain controlled degenerations of such maps and describe how one can implement jumps from one homotopy class to another while allowing only "small" degenerations.