arXiv subjects
Publications and source records attributed to Andrew H. Hoefel.
We describe the graded characters and Hilbert functions of certain graded artinian Gorenstein quotients of the polynomial ring which are also representations of the symmetric group. Specifically, we look at those algebras whose socles are trivial representations and whose principal apolar submodules are generated by the sum of the orbit of a power of a linear form.
We investigate symbolic and regular powers of monomial ideals. For a square-free monomial ideal $I$ in $k[x_0, \ldots, x_n]$ we show $I^{t(m+e-1)-e+r)}$ is a subset of $M^{(t-1)(e-1)+r-1}(I^{(m)})^t$ for all positive integers $m$, $t$ and $r$, where $e$ is the big-height of $I$ and $M = (x_0, \ldots, x_n)$. This captures two conjectures ($r=1$ and $r=e$): one of Harbourne-Huneke and one of Bocci-Cooper-Harbourne. We also introduce the symbolic polyhedron of a monomial ideal and use this to explore symbolic powers of non-square-free monomial ideals.
Let $G$ be a graph with chordal complement and $I(G)$ its edge ideal. From work of Herzog, Hibi, and Zheng, it is known that $I(G)$ has linear quotients and all of its powers have linear resolutions. For edge ideals $I(G)$ arising from graphs which do not have chordal complements, exact conditions on their powers possessing linear resolutions or linear quotients are harder to find. We provide here an explicit linear quotients ordering for all powers of the edge ideal of the antipath and a linear quotients ordering on the second power of $I(A_n)^2$ of the edge ideal of the anticycle $A_n$. This linear quotients ordering on $I(A_n)$ recovers a prior result of Nevo that $I(A_n)^2$ has a linear resolution.
We classify the squarefree ideals which are Gotzmann in a polynomial ring.
Let P = k[x_1, ..., x_n] be the polynomial ring in n variables. A homogeneous ideal I of P generated in degree d is called Gotzmann if it has the smallest possible Hilbert function out of all homogeneous ideals with the same dimension in degree d. The edge ideal of a simple graph G on vertices x_1, ..., x_n is the quadratic square-free monomial ideal generated by all x_i x_j where {x_i,x_j} is an edge of G. The only edge ideals that are Gotzmann are those edge ideals corresponding to star graphs.