A NONSYMMETRIC VERSION OF OKOUNKOV’S BC-TYPE INTERPOLATION MACDONALD POLYNOMIALS

Nonsymmetric interpolation Laurent polynomials in n variables are introduced, with the interpolation points depending on q and on a n-tuple of parameters τ = (τ1, …, τn). When τi = stn − 1, Okounkov’s 3-parameter BCn-type interpolation Macdonald polynomials are recovered from the nonsymmetric interpolation Laurent polynomials through Hecke algebra symmetrisation with respect to a type Cn Hecke algebra action. In the Appendix we give some conjectures about extra vanishing, based on Mathematica computations in rank two.