“…The (small) equivariant quantum K-theory ring QK T (X) of Givental [Giv00] is a common generalization of the main cohomology theories considered in Schubert calculus, including K-theory, equivariant cohomology, and quantum cohomology. Equivariant quantum Ktheory is the most general theory for which the associated Schubert structure constants have positivity properties that are either known [Gra01,Mih06b,Bri02,AGM11,AC15] or conjectured [LM06,LP07,BM11]. In this paper, we prove a Chevalley formula that combinatorially determines the ring QK T (X) when X is a cominuscule variety, that is, a Grassmann variety Gr(m, n) of type A, a Lagrangian Grassmannian LG(n, 2n), a maximal orthogonal Grassmannian OG(n, 2n), a quadric hypersurface Q n , or one of two exceptional varieties called the Cayley plane E 6 /P 6 and the Freudenthal variety E 7 /P 7 .…”