Linear preservers of secant varieties and other varieties of tensors
Fulvio Gesmundo, Young In Han, Benjamin Lovitz
TL;DR
The paper develops a unified framework for the linear preserver problem of algebraic varieties, focusing on secant varieties of Segre and related tensor varieties. It combines Lie algebra methods, prolongation of ideals, singular-locus analysis, and dual-geometry arguments to determine preservers in broad tensor settings, including many Secant varieties with the expected preserver $G_X=G(V_1,\dots,V_k)\rtimes \widetilde{\mathfrak{S}}$. A central result shows that $\sigma_r((\mathbb{P}^{n-1})^{\times k})$ has the expected preserver for all $r \le n^{\lfloor k/2 \rfloor}$, and the authors extend the analysis to subspace varieties, partition varieties, Waring-rank strata, and certain quantum-state classes such as biseparable and fully separable tensors. The work provides both structural theorems and computational techniques, with applications to quantum information and a range of tensor-geometry problems, while also offering geometric proofs of several known preservers.
Abstract
We study the problem of characterizing linear preserver subgroups of algebraic varieties, with a particular emphasis on secant varieties and other varieties of tensors. We introduce a number of techniques built on different geometric properties of the varieties of interest. Our main result is a simple characterization of the linear preservers of secant varieties of Segre varieties in many cases, including $σ_r((\mathbb{P}^{n-1})^{\times k})$ for all $r \leq n^{\lfloor k/2 \rfloor}$. We also characterize the linear preservers of several other sets of tensors, including subspace varieties, the variety of slice rank one tensors, symmetric tensors of bounded Waring rank, the variety of biseparable tensors, and hyperdeterminantal surfaces. Computational techniques and applications in quantum information theory are discussed. We provide geometric proofs for several previously known results on linear preservers.
