  Stable Grothendieck polynomials can be viewed as a K-theory analog of Schur
polynomials. We extend stable Grothendieck polynomials to a two-parameter
version, which we call canonical stable Grothendieck functions. These functions
have the same structure constants (with scaling) as stable Grothendieck
polynomials, and (composing with parameter switching) are self-dual under the
standard involutive ring automorphism. We study various properties of these
functions, including combinatorial formulas, Schur expansions, Jacobi-Trudi
type identities, and associated Fomin-Greene operators.
