We describe the structure of monoid natural-valued monotone functions on an arbitrary poset. For this we provide a presentation, characterization prime elements, and description its convex hull. also study associated ring, proving that it is normal, thus Cohen-Macaulay. determine Cohen-Macaulay type, characterize Gorenstein property, Gröbner basis defining ideal. Then apply these results to qua...

Let k be an algebraically closed field of characteristic zero, S = k[X0, X1, X2, X3, X4] and P = Proj(S). By a curve we always mean a closed one-dimensional subscheme of P which is locally Cohen-Macaulay and equidimensional. The main purpose of this paper is to show that arithmetically Cohen-Macaulay curves C ⊂ P lying on a “general” arithmetically Cohen-Macaulay surface X ⊂ P with degree matri...

‎in this paper‎, ‎we give some necessary conditions for an $r$-partite graph such that the edge ring of the graph is cohen-macaulay‎. ‎it is proved that if there exists a cover of an $r$-partite cohen-macaulay graph by disjoint cliques of size $r$‎, ‎then such a cover is unique‎.

The aim of this paper is to investigate properties of the local cohomology of rings of mixed characteristic that are analogous to Segre products of rings de ned over a eld. The main question is whether the local cohomology can be almost killed in a nite extension (we de ne what this means below). There are two reasons for considering this type of ring. First, there are special properties of the...

We examine some recent work of Phillip Griffith on étale covers and fibered products from the point of view of tight closure theory. While it is known that cyclic covers of Gorenstein rings with rational singularities are Cohen-Macaulay, we show this is not true in general in the absence of the Gorenstein hypothesis. Specifically, we show that the canonical cover of a Q-Gorenstein ring with rat...

We study in detail locally Cohen-Macaulay curves in P 3 which are contained in a double plane 2H , thus completing the classification of curves lying on surfaces of degree two. We describe the irreducible components of the Hilbert schemes Hd,g(2H) of locally Cohen-Macaulay curves in 2H of degree d and arithmetic genus g, and we show that Hd,g(2H) is connected. We also discuss the Rao module of ...