Séminaire Lotharingien de Combinatoire, 78B.67 (2017), 12 pp.

Voula Collins

A Puzzle Formula for H*T x Cx(T*Pn)

Abstract. We will begin with the work of Davesh Maulik and Andrei Okounkov where they define a "stable basis" for the T-equivariant cohomology ring H*T x Cx(T*Grk(Cn)), of the cotangent bundle to a Grassmannian. Just as we can compute the product structure of the the cohomology ring of a Grassmannian using Schubert classes as a basis, it is natural to attempt to do the same for the cotangent bundle to a Grassmannian using these Maulik-Okounkov classes as a basis. In this paper I compute the structure constants of both the regular and equivariant cohomology rings of the cotangent bundle to projective space, using Maulik-Okounkov classes as a basis. First I do so directly in Theorem 3.1, and then I put forth a conjectural positive formula, which uses a variant of Knutson-Tao puzzles, in Conjecture 4.2. The proof of the puzzle formula relies on an explicit rational function identity that I have checked through dimension 9.

Received: November 14, 2016. Accepted: February 17, 2017. Final version: April 1, 2017.

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