Abstract

We give an overview of different characterisations of L∞-structures in terms of symmetric brackets and (co)differentials on the symmetric (co)algebra. We then do the same for their representations (up to homotopy) and approach L∞-algebra cohomology using the commutator bracket on the space of coderivations of the symmetric coalgebra. This leads to abelian extensions of L∞-algebras by 2-cocycles.

Highlights

  • L∞-algebras were first introduced in [1] and [2] and are a generalisation of graded Lie algebras in which a system of antisymmetric n-ary brackets satisfies a generalised Jacobi identity

  • The first part of this article serves as a self-contained introduction to L∞-algebras, in which we discuss different characterisations of L∞-algebras and their representations, closely following [3]

  • The L∞-algebra cohomology with values in the adjoint representation was introduced in [4] using a Lie bracket on the space of cochains

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Summary

Introduction

L∞-algebras ( called strongly homotopy Lie algebras) were first introduced in [1] and [2] and are a generalisation of graded Lie algebras in which a system of antisymmetric n-ary brackets satisfies a generalised Jacobi identity. The first part of this article serves as a self-contained introduction to L∞-algebras, in which we discuss different characterisations of L∞-algebras and their representations (up to homotopy), closely following [3]. The L∞-algebra cohomology with values in the adjoint representation was introduced in [4] using a Lie bracket on the space of cochains We extend this approach to arbitrary representations, which leads to a characterisation of certain L∞-algebras as abelian extensions of L∞-algebras by 2-cocycles. This generalises a theorem from [5] that characterises certain L∞-algebras in terms of Lie algebra cohomology. This article is largely based on my same-titled Bachelor’s thesis, which I wrote under the supervision of Chenchang Zhu at the University of Gottingen in 2018

Mathematical background
Graded vector spaces
Reinhold
Graded algebras
Graded coalgebras
Coaugmented coalgebras
Comodules and coderivations
Dual spaces
Symmetric brackets and codifferentials
Characterisation via Lie algebra cohomology
Weak homomorphisms
Representations as coderivations
A dead-end
Abelian and central extensions
Semidirect sums
Full Text
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