W-algebras Associated to Truncated Current Lie Algebras

Authors: He, Xiao
Advisor: Lau, Michael
Abstract: Given a finite-dimensional semi-simple Lie algebra g and a non-zero nilpotent element e 2 g, one can construct various W-algebras associated to (g; e). Among them, the affine W-algebra is a vertex algebra which can be realized through semi-infinite cohomology, and the finite W-algebra is the Zhu algebra of the affineW-algebra. In the constructions ofW-algebras, a non-degenerate invariant bilinear form and a good Z-grading of g play essential roles. Truncated current Lie algebras associated to g are quotients of the current Lie algebra g C[t]. One can show that non-degenerate invariant bilinear forms exist on truncated current Lie algebras and a good Z-grading of g induces good Z-gradings of truncated current Lie algebras. The constructions of W-algebras can thus be adapted to the setting of truncated current Lie algebras. The main results of this thesis are as follows. First, we introduce finite and affine W-algebras associated to truncated current Lie algebras and generalize some properties of W-algebras associated to semi-simple Lie algebras. Second, we develop an adjusted version of semi-infinite cohomology, which helps us to define affine W-algebras associated to general nilpotent elements in a uniform way. Finally, we consider vertex operator algebras in general, and show that their higher level Zhu algebras are all isomorphic to subquotients of their universal enveloping algebras.
Document Type: Thèse de doctorat
Issue Date: 2018
Open Access Date: 9 July 2018
Permalink: http://hdl.handle.net/20.500.11794/30327
Grantor: Université Laval
Collection:Thèses et mémoires

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