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    • CommentRowNumber1.
    • CommentAuthorUrs
    • CommentTimeFeb 23rd 2017
    • (edited Feb 23rd 2017)

    I gave Jones’ theorem (long requested at Hochschild homology) a quick statement and references. Copied this also to the entries free loop space, cyclic loop space and cyclic homology and Sullivan models of free loop spaces:

    Let XX be a simply connected topological space.

    The ordinary cohomology H H^\bullet of its free loop space is the Hochschild homology HH HH_\bullet of its singular chains C (X)C^\bullet(X):

    H (X)HH (C (X)). H^\bullet(\mathcal{L}X) \simeq HH_\bullet( C^\bullet(X) ) \,.

    Moreover the S 1S^1-equivariant cohomology of the loop space, hence the ordinary cohomology of the cyclic loop space X/ hS 1\mathcal{L}X/^h S^1 is the cyclic homology HC HC_\bullet of the singular chains:

    H (X/ hS 1)HC (C (X)) H^\bullet(\mathcal{L}X/^h S^1) \simeq HC_\bullet( C^\bullet(X) )

    (Loday 11)

    If the coefficients are rational, and XX is of finite type then this may be computed by the Sullivan model for free loop spaces, see there the section on Relation to Hochschild homology.

    In the special case that the topological space XX carries the structure of a smooth manifold, then the singular cochains on XX are equivalent to the dgc-algebra of differential forms (the de Rham algebra) and hence in this case the statement becomes that

    H (X)HH (Ω (X)). H^\bullet(\mathcal{L}X) \simeq HH_\bullet( \Omega^\bullet(X) ) \,. H (X/ hS 1)HC (Ω (X)). H^\bullet(\mathcal{L}X/^h S^1) \simeq HC_\bullet( \Omega^\bullet(X) ) \,.

    This is known as Jones’ theorem (Jones 87)

    An infinity-category theoretic proof of this fact is indicated at Hochschild cohomology – Jones’ theorem.

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