# ag网站亚游登录,ag亚集团官方网站

Southwest Jiaotong University School of Mathematics

### 信息与计算科学系

ag网站亚游登录  >  学术科研  >  信息与计算科学系  >  正文

# 学术报告：Convex polytopes and minimum ranks of nonnegative sign pattern matrices

ag网站亚游登录：   作者：许仁誉     日期：2019-06-24 22:51:17   点击数：

A sign pattern matrix (resp., nonnegative sign pattern matrix) is a matrix whose entries are from the set {+, -, 0}. The minimum rank (resp., rational minimum rank) of a sign pattern matrix A is the minimum of the ranks of the matrices (resp., rational matrices) whose entries have signs equal to the corresponding entries of A. Using a correspondence between sign patterns with minimum rank $r\geq 2$ and point-hyperplane configurations in R^{r-1} and Steinitz's theorem on the rational realizability of 3-polytopes, it is shown that for every nonnegative sign pattern of minimum rank at most 4, the minimum rank and the rational minimum rank are equal. But there are nonnegative sign patterns with minimum rank 5 whose rational minimum rank is greater than 5. It is established that every d- polytope determines a nonnegative sign pattern with minimum rank d+1 that has a (d+1)\times (d+1) triangular submatrix with all diagonal entries positive. It is also shown that there are at most \min { 3m, 3n } zero entries in any condensed nonnegative m \times n sign pattern of minimum rank 3. Some bounds on the entries of some integer matrices achieving the minimum ranks of nonnegative sign patterns with minimum rank 3 or 4 are established