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University of Cambridge > Talks.cam > Isaac Newton Institute Seminar Series > A lower bound of a sub-quotient of the Lie algebra associated to Grothendieck-Teichmller group

## A lower bound of a sub-quotient of the Lie algebra associated to Grothendieck-Teichmller groupAdd to your list(s) Download to your calendar using vCal - Enriquez, B (University of Strasbourg)
- Thursday 18 April 2013, 16:00-18:00
- Seminar Room 2, Newton Institute Gatehouse.
If you have a question about this talk, please contact Mustapha Amrani. Grothendieck-Teichmller Groups, Deformation and Operads We show that the filtration given by the central descending series of the commutator of the free Lie algebra on two generators x,y induces by a filtration of the graded Lie algebra grt_1 associated to the Grothendieck-Teichmller group. The degree 0 part of the associated graded space has already been computed (by the collaborator of the author). We get here a lower bound for the degree 1 part; more precisely, this graded space splits into a sum of homogeneous components, on which we get a filtration and we give a lower bound for the dimensions of each sub-quotient. The proof uses the construction of a vector space included in certain Lie sub-algebras of extensions between abelian Lie algebras, and reduces the problem to a question of commutative algebras, which is treated with invariant theory and results of Ihara, Takao, and Schneps on the quadratic relations between elements of the degree 1 part associated to grt_1 for the depth filtration (corresponding to the y-degree). As a corollary, we give another proof of a statement of Ecalle describing the sub-space of the degree 2 part of the same graded space. This talk is part of the Isaac Newton Institute Seminar Series series. ## This talk is included in these lists:- All CMS events
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