Title: Euler characteristics of cominuscule quantum K-theory,
Abstract: We prove an identity relating the product of two opposite Schubert varieties
in the (equivariant) quantum K-theory ring of a cominuscule flag variety to the
minimal degree of a rational curve connecting the Schubert varieties. We deduce
that the sum of the structure constants associated to any product of Schubert
classes is equal to one. Equivalently, the sheaf Euler characteristic map
extends to a ring homomorphism defined on the quantum K-theory ring.