This paper is concerned with the problem of Boolean approximation in the following sense: given a Boolean function class and an arbitrary Boolean function, what is the function’s best proxy in the class? Specifically, what is its strongest logical consequence (or envelope) in the class of affine Boolean functions. We prove various properties of affine Boolean functions and their representation ...

Confirming a conjecture of Mark Shimozono, we identify polynomial representatives for the Schubert classes of the affine Grassmannian as the k-Schur functions in homology and affine Schur functions in cohomology. Our results rely on Kostant and Kumar’s nilHecke ring, work of Peterson on the homology of based loops on a compact group, and earlier work of ours on non-commutative k-Schur functions.

Little [Adv. Math. 174 (2003), 236–253] developed a combinatorial algorithm to study the Schur-positivity of Stanley symmetric functions and the Lascoux–Schützenberger tree. We generalize this algorithm to affine Stanley symmetric functions, which were introduced recently in [T. Lam: “Affine Stanley symmetric functions,” Amer. J. Math., to appear].

We study t-analogs of string functions for integrable highest weight representations of the affine Kac-Moody algebra A (1) 1 . We obtain closed form formulas for certain t-string functions of levels 2 and 4. As corollaries, we obtain explicit identities for the corresponding affine Hall-Littlewood functions, as well as higher-level generalizations of Cherednik’s Macdonald and Macdonald-Mehta co...

We proved affine planes corresponding to quadratic planar functions over Fpn are semifield planes, and we determined affine planes corresponding to planar functions f(x) = x10 − αx6 − α2x2 by Ding and Yuan. Moreover we calculated explicit shapes of planar functions from the square mappings of almost all known finite commutative semifields.

This paper explores the existence of affine invariant descent directions for unconstrained minimization. While there may exist several affine invariant descent directions for smooth functions f at a given point, it is shown that for quadratic functions there exists exactly one invariant descent direction in the strictly convex case and generally none in the nondegenerate indefinite case. These ...