Open -ranks with respect to Segre and Veronese varieties

Abstract

Let be an integral and non-degenerate variety. Recall (A. Bialynicki-Birula, A. Schinzel, J. Jelisiejew and others) that for any the open rank is the minimal positive integer such that for each closed set there is a set with and , where denotes the linear span. For an arbitrary we give an upper bound for in terms of the upper bound for when is a point in the maximal proper secant variety of and a similar result using only points with submaximal border rank. We study when is a Segre variety (points with -rank and ) and when is a Veronese variety (points with -rank or with border rank ).