Typical ranks for 3-tensors, nonsingular bilinear maps and determinantal ideals

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• 作者：Toshio Sumi^a ; ^{sumi@artsci.kyushu-u.ac.jp" class="auth_mail" title="E-mail the corresponding author} ; Mitsuhiro Miyazaki^b ; ^{g53448@kyokyo-u.ac.jp" class="auth_mail" title="E-mail the corresponding author} ; Toshio Sakata^c ; ^{sakatastat@gmail.com" class="auth_mail" title="E-mail the corresponding author}
• 关键词：15A69 ; 13C40 ; 14M12 ; 14P10
• 刊名：Journal of Algebra
• 出版年：2017
• 出版时间：1 February 2017
• 年：2017
• 卷：471
• 期：Complete
• 页码：409-453
• 全文大小：701 K

文摘

Let 88" title="Click to view the MathML source">m,n≥3$m,n\ge 3$, e695f77a7f939780026741465" title="Click to view the MathML source">(m−1)(n−1)+2≤p≤mn$(m-1)(n-1)+2\le p\le mn$, and u=mn−p$u=mn-p$. The set R^u×n×m${\mathbb{R}}^{u\times n\times m}$ of all real tensors with size a27cf985" title="Click to view the MathML source">u×n×m$u\times n\times m$ is one to one corresponding to the set of bilinear maps a135fb0" title="Click to view the MathML source">R^m×Rⁿ→R^u${\mathbb{R}}^m\times {\mathbb{R}}^n\to {\mathbb{R}}^u$. We show that R^m×n×p${\mathbb{R}}^{m\times n\times p}$ has plural typical ranks p   and p+1$p+1$ if and only if there exists a nonsingular bilinear map a135fb0" title="Click to view the MathML source">R^m×Rⁿ→R^u${\mathbb{R}}^m\times {\mathbb{R}}^n\to {\mathbb{R}}^u$. We show that there is a dense open subset a13e438fac" title="Click to view the MathML source">O$\mathcal{O}$ of R^u×n×m${\mathbb{R}}^{u\times n\times m}$ such that for any 82d6a8d34" title="Click to view the MathML source">Y∈O$Y\in \mathcal{O}$, the ideal of maximal minors of a matrix defined by Y   in a certain way is a prime ideal and the real radical of that is the irrelevant maximal ideal if that is not a real prime ideal. Further, we show that there is a dense open subset T$\mathcal{T}$ of 884ca4e48167" title="Click to view the MathML source">R^n×p×m${\mathbb{R}}^{n\times p\times m}$ and continuous surjective open maps 826f14262b" title="Click to view the MathML source">ν:O→R^u×p$\nu :\mathcal{O}\to {\mathbb{R}}^{u\times p}$ and a116d748ca7bdb" title="Click to view the MathML source">σ:T→R^u×p$\sigma :\mathcal{T}\to {\mathbb{R}}^{u\times p}$, where 98a44" title="Click to view the MathML source">R^u×p${\mathbb{R}}^{u\times p}$ is the set of u×p$u\times p$ matrices with entries in a1b766c83" title="Click to view the MathML source">R$\mathbb{R}$, such that if a256103e587b25ca5" title="Click to view the MathML source">ν(Y)=σ(T)$\nu (Y)=\sigma (T)$, then e66c7d9980604628dcb00ee46b2">$\mathrm{rank}T=p$ if and only if the ideal of maximal minors of the matrix defined by Y is a real prime ideal.