#### Volume 3, issue 2 (2003)

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On a theorem of Kontsevich

### James Conant and Karen Vogtmann

Algebraic & Geometric Topology 3 (2003) 1167–1224
 arXiv: math.QA/0208169
##### Abstract

In [‘Formal (non)commutative symplectic geometry’, The Gelfand Mathematical Seminars (1990–1992) 173–187, and ‘Feynman diagrams and low-dimensional topology’, First European Congress of Mathematics, Vol. II Paris (1992) 97–121] M Kontsevich introduced graph homology as a tool to compute the homology of three infinite dimensional Lie algebras, associated to the three operads ‘commutative,’ ‘associative’ and ‘Lie.’ We generalize his theorem to all cyclic operads, in the process giving a more careful treatment of the construction than in Kontsevich’s original papers. We also give a more explicit treatment of the isomorphisms of graph homologies with the homology of moduli space and $Out\left({F}_{r}\right)$ outlined by Kontsevich. In [‘Infinitesimal operations on chain complexes of graphs’, Mathematische Annalen, 327 (2003) 545–573] we defined a Lie bracket and cobracket on the commutative graph complex, which was extended in [James Conant, ‘Fusion and fission in graph complexes’, Pac. J. 209 (2003), 219–230] to the case of all cyclic operads. These operations form a Lie bi-algebra on a natural subcomplex. We show that in the associative and Lie cases the subcomplex on which the bi-algebra structure exists carries all of the homology, and we explain why the subcomplex in the commutative case does not.

##### Keywords
cyclic operads, graph complexes, moduli space, outer space
##### Mathematical Subject Classification 2000
Primary: 18D50
Secondary: 57M27, 32D15, 17B65
##### Publication
Received: 5 February 2003
Revised: 1 December 2003
Accepted: 11 December 2003
Published: 12 December 2003
##### Authors
 James Conant Department of Mathematics University of Tennessee Knoxville TN 37996 USA Karen Vogtmann Department of Mathematics Cornell University Ithaca, NY 14853-4201 USA