The determinantal ideals of extended Hankel matrices

Abstract

In this paper, we use the tools of Gröbner bases and combinatorial secant varieties to study the determinantal ideals $I_t$ of the extended Hankel matrices. Denote by $c$-chain a sequence $a_1,\dot{.}.,a_k$ with $a_i+c<a_{i+1}$ for all $i=1,\dot{.}.,k-1$. Using the results of $c$-chain, we solve the membership problem for the symbolic powers $I_t^{(s)}$ and we compute the primary decomposition of the product $I_{t_1}\dot{.}.I_{t_k}$ of the determinantal ideals. Passing through the initial ideals and algebras we prove that the product $I_{t_1}\dot{.}.I_{t_k}$ has a linear resolution and the multi-homogeneous Rees algebra $\Rees(I_{t_1},\...,I_{t_k})$ is defined by a Gröbner basis of quadrics.