The monic rank

Arthur Bik, Jan Draisma, Alessandro Oneto, Emanuele Ventura

Research output: Contribution to journalArticleAcademicpeer-review


We introduce the monic rank of a vector relative to an affine-hyperplane section of an irreducible Zariski-closed affine cone $ X$. We show that the monic rank is finite and greater than or equal to the usual $ X$-rank. We describe an algorithmic technique based on classical invariant theory to determine, in concrete situations, the maximal monic rank. Using this technique, we establish three new instances of a conjecture due to B. Shapiro which states that a binary form of degree $ d\cdot e$ is the sum of $ d$ $ d$th powers of forms of degree $ e$. Furthermore, in the case where $ X$ is the cone of highest weight vectors in an irreducible representation--this includes the well-known cases of tensor rank and symmetric rank--we raise the question whether the maximal rank equals the maximal monic rank. We answer this question affirmatively in several instances.
Original languageEnglish
Pages (from-to)2481-2505
Number of pages25
JournalMathematics of Computation
Issue number325
Publication statusPublished - 2020


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