Hochschild–Kostant–Rosenberg Theorem

An isomorphism identifying the Hochschild homology of a smooth commutative algebra with its algebraic differential forms: for a smooth commutative k-algebra A (under the usual hypotheses, e.g.

A theorem identifying the Hochschild homology HH_*(A) of a smooth commutative algebra A (or smooth algebraic variety) with the algebra of differential forms Ω^*_A, via the Hochschild–Kostant–Rosenberg (HKR) map, thereby linking homological algebra to differential geometry in the smooth commutative setting.