Disproving Hibi's Conjecture with CoCoA or Projective Curves with bad Hilbert Functions

Abstract

In this paper we show how to combine different techniques from Commutative Algebra and a systematic use of a Computer Algebra System (in our case mainly CoCoA) in order to explicitly construct Cohen-Macaulay domains, which are standard $k$-algebras and whose Hilbert function is ``bad". In particular we disprove a well-known conjecture by Hibi.