Volume 11, issue 2 (2011)

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Differential operators and the wheels power series

Andrew Kricker

Algebraic & Geometric Topology 11 (2011) 1107–1162
Abstract

An earlier work of the author’s showed that it was possible to adapt the Alekseev–Meinrenken Chern–Weil proof of the Duflo isomorphism to obtain a completely combinatorial proof of the wheeling isomorphism. That work depended on a certain combinatorial identity, which said that a particular composition of elementary combinatorial operations arising from the proof was precisely the wheeling operation. The identity can be summarized as follows: The wheeling operation is just a graded averaging map in a space enlarging the space of Jacobi diagrams. The purpose of this paper is to present a detailed and self-contained proof of this identity. The proof broadly follows similar calculations in the Alekseev–Meinrenken theory, though the details here are somewhat different, as the algebraic manipulations in the original are replaced with arguments concerning the enumerative combinatorics of formal power series of graphs with graded legs.

Keywords
Lie algebra, Jacobi diagram, wheeling isomorphism, combinatorics
Mathematical Subject Classification 2000
Primary: 17B99, 57M25
Secondary: 05E99