We prove a
Giambelli formula for the Peterson Schubert classes in the
-equivariant cohomology
ring of a type
Peterson variety. The proof uses the Monk formula for the equivariant
structure constants for the Peterson Schubert classes derived by Harada and
Tymoczko. In addition, we give proofs of two facts observed by H. Naruse:
firstly, that some constants that appear in the multiplicative structure of the
-equivariant
cohomology of Peterson varieties are Stirling numbers of the second kind, and
secondly, that the Peterson Schubert classes satisfy a stability property in a sense
analogous to the stability of the classical equivariant Schubert classes in the
-equivariant
cohomology of the flag variety.
Department of Pure Mathematics and
Mathematical Statistics
Centre for Mathematical Sciences
University of Cambridge
Wilberforce Road
Cambridge CB30WA
United Kingdom