English

Typical and Admissible ranks over fields

Algebraic Geometry 2016-04-11 v1 Commutative Algebra

Abstract

Let X(\RR)X(\RR) be a geometrically connected variety defined over \RR\RR and such that the set of all its (also complex) points X(\CC)X(\CC) is non-degenerate. We introduce the notion of \emph{admissible rank} of a point PP with respect to XX to be the minimal cardinality of a set of points of X(\CC)X(\CC) such that PSP\in \langle S \rangle that is stable under conjugation. Any set evincing the admissible rank can be equipped with a \emph{label} keeping track of the number of its complex and real points. We show that in the case of generic identifiability there is an open dense euclidean subset of points with certain admissible rank for any possible label. Moreover we show that if XX is a rational normal curve than there always exists a label for the generic element. We present two examples in which either the label doesn't exists or the admissible rank is strictly bigger than the usual complex rank.

Keywords

Cite

@article{arxiv.1604.02342,
  title  = {Typical and Admissible ranks over fields},
  author = {Edoardo Ballico and Alessandra Bernardi},
  journal= {arXiv preprint arXiv:1604.02342},
  year   = {2016}
}

Comments

12 pages, Comments welcome

R2 v1 2026-06-22T13:28:07.969Z