Holmstrom HKR theorem

Hochschild-Kostant-Rosenberg I think. See also Hochschild cohomology.

http://mathoverflow.net/questions/35777/hochschild-and-cyclic-homology-of-smooth-varieties

http://ncatlab.org/nlab/show/Hochschild-Kostant-Rosenberg+theorem

http://mathoverflow.net/questions/14861/is-there-a-refinement-of-the-hochschild-kostant-rosenberg-theorem-for-cohomology

http://mathoverflow.net/questions/16960/hochschild-kostant-rosenberg-theorem-for-varieties-in-positive-characteristic

Toen: Algebres simplicicales etc, file Toen web prepr rhamloop.pdf. Comparison between functions on derived loop spaces and de Rham theory. Take a smooth k-algebra, k aof char zero. Then (roughly) the de Rham algebra of A and the simplical algebra $S^1 \otimes A$ determine each other (functorial equivalence). Consequence: For a smooth k-scheme $X$, the algebraic de Rham cohomology is identified with $S^1$-equivariant functions on the derived loop space of $X$. Conjecturally this should follow from a more general comparison between functions on the derived loop space and cyclic homology. Also functorial and multiplicative versions of HKR type thms on decompositions of Hochschild cohomology, for any separated k-scheme.

nLab page on HKR theorem