Periodic trivial extension algebras and fractionally Calabi-Yau algebras
arXiv:2012.11927
Abstract
We study periodicity and twisted periodicity of the trivial extension algebra of a finite-dimensional algebra . Our main results show that (twisted) periodicity of is equivalent to being (twisted) fractionally Calabi-Yau of finite global dimension. We also extend this result to a large class of self-injective orbit algebras. As a significant consequence, these results give a partial answer to the periodicity conjecture of Erdmann-Skowroński, which expects the classes of periodic and twisted periodic algebras to coincide. On the practical side, it allows us to construct a large number of new examples of periodic algebras and fractionally Calabi-Yau algebras. We also establish a connection between periodicity and cluster tilting theory, by showing that twisted periodicity of is equivalent the -representation-finiteness of the -fold trivial extension algebra for some . This answers a question by Darpö and Iyama. As applications of our results, we give answers to some other open questions. We construct periodic symmetric algebras of wild representation type with arbitrary large minimal period, answering a question by Skowroński. We also show that the class of twisted fractionally Calabi-Yau algebras is closed under derived equivalence, answering a question by Herschend and Iyama.
42 pages. V2: New section 7 extending the main results from trivial extensions to orbit algebras. V3: Abstract updated. V4: Added an appendix explaining how QPA can be used to verify the fractional Calabi-Yau properties of algebras. Other minor updates