Given a smooth oriented manifold M with non-empty boundary, we study the Pontryagin algebra A = H * (Ω) where Ω is the space of loops in M based at a distinguished point of ∂M . Using the ideas of string topology of Chas-Sullivan, we define a linear map { {−, −} } : A ⊗ A → A ⊗ A which is a double bracket in the sense of Van den Bergh satisfying a version of the Jacobi identity. For dim(M ) ≥ 3, the double bracket { {−, −} } induces Gerstenhaber brackets in the representation algebras associated with A. This extends our previous work on the case dim(M ) = 2 where A = H 0 (Ω) is the group algebra of the fundamental group π 1 (M ) and the double bracket { {−, −} } induces the standard Poisson brackets on the moduli spaces of representations of π 1 (M ). Contents Introduction Chapter 1. Algebras, brackets, and bibrackets 1.1. Algebras and brackets 1.2. Bibrackets 1.3. Equivariance 1.4. The associated pairing and the trace Chapter 2. Bibrackets in unital algebras and in categories 2.1. Bibrackets in unital algebras 2.2. Bibrackets in categories 2.3. Bibrackets in Hopf categories 2.4. Hamiltonian reduction of bibrackets Chapter 3. Face homology 3.1. Manifolds with faces and partitions 3.2. Polychains, polycycles, and face homology 3.3. Face homology versus singular homology 3.4. Smooth polychains Chapter 4. Operations on polychains 4.1. Transversality in path spaces 4.2. Intersection of polychains 4.3. The operation Υ 4.4. The operation Υ Chapter 5. The intersection bibracket 5.1. Construction of the intersection bibracket 5.2. The Jacobi identity 5.3. Computations and examples Chapter 6. Properties of the intersection bibracket 6.1. The scalar intersection form 6.2. The reducibility 6.3. The string bracket 6.4. Moment maps and Hamiltonian reduction Bibliography IndexConventions. Throughout the memoir, the letter K denotes a commutative ring which serves as the ground ring of all modules and algebras. Thus, by a module (respectively, an algebra, a linear map) we mean a K-module (respectively, a Kalgebra, a K-linear map). By the singular homology of a topological space we mean singular homology with coefficients in K.Given a smooth oriented manifold M and a smooth orientable submanifold N ⊂ M , an orientation of the normal bundle of N in M determines an orientation of N , and vice versa, via the following rule: a positive frame in the normal bundle of N followed by a positive frame in the tangent bundle of N is a positive frame in the tangent bundle of M . If ∂M = ∅, then the orientation of M induces an orientation of ∂M using the "outward vector first" rule.
CHAPTER 1Algebras, brackets, and bibrackets
Algebras and bracketsWe start by recalling some standard terminology.1.1.1. Graded modules and graded algebras. By a graded module we mean a Z-graded module A = ⊕ p∈Z A p (over K). An element a of A is homogeneous if a ∈ A p for some p; we write then |a| = p and call |a| the degree of a. By definition, the degree of 0 ∈ A is an arbitrary integer. For any d ∈ Z, the d-degreeA graded algebra is a graded module A endowed wi...