In this paper we prove parts of a conjecture of Herzog giving lower bounds on the rank of the free modules appearing in the linear strand of a graded k-th syzygy module over the polynomial ring. If in addition the module is Z n-graded we show that the conjecture holds in full generality. Furthermore, we give lower and upper bounds for the graded Betti numbers of graded ideals with a linear reso...

Let R = k[x 1 ,. .. , xn] and let I be the ideal of n + 1 generically chosen forms of degrees d 1 ≤ · · · ≤ d n+1. We give the precise graded Betti numbers of R/I in the following cases: • n = 3; • n = 4 and 5 i=1 d i is even; • n = 4, 5 i=1 d i is odd and d 2 + d 3 + d 4 < d 1 + d 5 + 4; • n is even and all generators have the same degree, a, which is even; • (n+1 i=1 d i) − n is even and d 2 ...

We consider the following open questions. Fix a Hilbert function h, that occurs for a reduced zero-dimensional subscheme of P. Among all subschemes, X, with Hilbert function h, what are the possible Hilbert functions and graded Betti numbers for the first infinitesimal neighborhood, Z, of X (i.e. the double point scheme supported on X)? Is there a minimum (h) and maximum (h) such function? The ...

Let S be a polynomial ring in n variables over a field K of characteristic 0. A numerical characterization of all possible extremal Betti numbers of any graded submodule of a finitely generated graded free S-module is given. 2010 Mathematics Subject Classification: 13B25, 13D02, 16W50.

Let I(G) be the edge ideal associated to a simple graph G. We study the graded Betti numbers that appear in the linear strand of the minimal free resolution of I(G).

Let I(G) be the edge ideal associated to a simple graph G. We study the graded Betti numbers that appear in the linear strand of the minimal free resolution of I(G).

We define the reduced horseshoe resolution and the notion of conjoined pairs of ideals in order to study the minimal graded free resolution of a class of p-Borel ideals and recover Pardue’s regularity formula for them. It will follow from our technique that the graded betti numbers of these ideals do not depend on the characteristic of the base field k.

We show the secant variety of a linearly normal smooth curve of degree at least 2g + 3 is arithmetically Cohen-Macaulay, and we use this information to study the graded Betti numbers of the secant variety.