Subcanonical Graded Rings Which Are Not Cohen-Macaulay, with Appendix: A non-Q-Gorenstein Cohen-Macaulay cone X with K_X Q-Cartier

Fabrizio Catanese, Appendix by Jonathan Wahl

The paper answers a question by Jonathan Wahl,giving examples of regular surfaces S (so their canonical ring is a Gorenstein graded ring) having the following properties: 1) their…