Stabilization conjecture for the expected number of critical tensor approximations

Let XX be the tensor rank-one approximation variety, let dvd_v be the distance function determined by a Gaussian tensor vv, and let n1,,npn_1,\ldots,n_p denote the dimensions of the tensor factors. Suppose that

np1>i=1p1ni1.n_p-1>\sum_{i=1}^{p-1} n_i-1.

Stabilization conjecture. In the Gaussian setting of Theorem 1, the expected number of critical points of dvd_v on XX does not decrease when npn_p is replaced by np1n_p-1.

For p=2p=2, this follows because a sufficiently general n1×n2n_1\times n_2 matrix with n1<n2n_1<n_2 has n1n_1 singular values, and this number remains unchanged after replacing n2n_2 by n21n_2-1. Over C\mathbb{C}, the statement is known with equality, but a direct geometric argument explaining the corresponding real statement remains open. The smallest open case is p=3p=3 with (n1,n2,n3)=(2,2,4)(n_1,n_2,n_3)=(2,2,4), where the conjecture becomes the explicit integral inequality given in the source statement.

Sources & referencesView supporting material

Primary source

Jan Draisma and Emil Horobet, “The average number of critical rank-one approximations to a tensor”, arXiv:1408.3507 (2015).

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