Hopf actions on filtered regular algebras
  We study finite dimensional Hopf algebra actions on so-called filtered Artin-Schelter regular algebras of dimension n, particularly on those of dimension 2. The first Weyl algebra is an example of such on algebra with n=2, for instance. Results on the Gorenstein condition and on the global dimension of the corresponding fixed subrings are also provided. 
Kenneth Chan, Chelsea Walton, Yanhua Wang and James Zhang
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