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A combinatorial formula for the character of the diagonal coinvariants

J. Haglund, M. Haiman, N. Loehr, J. B. Remmel, and A. Ulyanov

Source: Duke Math. J. Volume 126, Number 2 (2005), 195-232.

Abstract

Let Rn be the ring of coinvariants for the diagonal action of the symmetric group Sn. It is known that the character of Rn as a doubly graded Sn-module can be expressed using the Frobenius characteristic map as $\nabla e_{n}$, where en is the nth elementary symmetric function and $\nabla $ is an operator from the theory of Macdonald polynomials. We conjecture a combinatorial formula for $\nabla e_{n}$ and prove that it has many desirable properties that support our conjecture. In particular, we prove that our formula is a symmetric function (which is not obvious) and that it is Schur positive. These results make use of the theory of ribbon tableau generating functions of Lascoux, Leclerc, and Thibon. We also show that a variety of earlier conjectures and theorems on $\nabla e_{n}$ are special cases of our conjecture.

Finally, we extend our conjectures on $\nabla e_{n}$ and several of the results supporting them to higher powers $\nabla^{m}e_{n}$.

Primary Subjects: 05E10
Secondary Subjects: 05A30, 20C30

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Permanent link to this document: http://projecteuclid.org/euclid.dmj/1106332719
Digital Object Identifier: doi:10.1215/S0012-7094-04-12621-1
Mathematical Reviews number (MathSciNet): MR2115257
Zentralblatt MATH identifier: 1069.05077

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