English

Hochschild (co)homology dimension

Rings and Algebras 2007-05-23 v1 Representation Theory

Abstract

In 1989 Happel conjectured that for a finite-dimensional algebra AA over an algebraically closed field kk, \glA<\gl A< \infty if and only if \hchA<\hch A < \infty. Recently Buchweitz-Green-Madsen-Solberg gave a counterexample to Happel's conjecture. They found a family of pathological algebra AqA_q for which \glAq=\gl A_q = \infty but \hchAq=2\hch A_q=2. These algebras are pathological in many aspects, however their Hochschild homology behaviors are not pathological any more, indeed one has \hhAq==\glAq\hh A_q = \infty=\gl A_q. This suggests to pose a seemingly more reasonable conjecture by replacing Hochschild cohomology dimension in Happel's conjecture with Hochschild homology dimension: \glA<\gl A < \infty if and only if \hhA<\hh A < \infty if and only if \hhA=0\hh A = 0. The conjecture holds for commutative algebras and monomial algebras. In case AA is a truncated quiver algebras these conditions are equivalent to the quiver of AA has no oriented cycles. Moreover, an algorithm for computing the Hochschild homology of any monomial algebra is provided. Thus the cyclic homology of any monomial algebra can be read off in case the underlying field is characteristic 0.

Keywords

Cite

@article{arxiv.math/0408402,
  title  = {Hochschild (co)homology dimension},
  author = {Yang Han},
  journal= {arXiv preprint arXiv:math/0408402},
  year   = {2007}
}

Comments

11 pages

R2 v1 2026-07-22T17:09:12.336Z