Secant Varieties Working Group 2018/2019
(follow up to Secant Varieties Working Group of Varieties: Arithmetic and Transformations)
in the winter semester of 2020/2021 meetings take place on:
Tuesday 9:3011:00, room 403

Research problems we try to address:
 Find membership test for secant variaties which do not apply for cactus varieties.
The initial work of the group in this direction is now available at arxiv: https://arxiv.org/abs/2007.16203
 For a fixed tensor find criteria for to have border rank equal to . (Arpan Pal from Texas A&M University is also working on this topic
https://www.math.tamu.edu/~arpantamu/)
 High rank loci. For let be the closure of tensors in which have rank equal to . Is there an equality between and for , where denotes the join of and ? (answer is no  recently solved by E. Ballico, A. Bernardi, E. Ventura
 For , where is generic from we want to find decomposition for . We would like to find an algorithm wich computes such a decomposition.
 For where are simple tensors with norm and is a random error with norm . Assuming we want to find the funcition such that is the best rank 2 approximation and the norms are bounded from above by some constant.
We are open to discuss any issues related to secant varieties, cactus varieties, tensor rank, Waring rank, and their border/cactus analogues, identifiability, apolarity, Hilbert schemes of points etc.
