# Tensor Rank and the Ill-Posedness of the Best Low-Rank Approximation Problem

@article{Silva2006TensorRA, title={Tensor Rank and the Ill-Posedness of the Best Low-Rank Approximation Problem}, author={Vin de Silva and Lek-Heng Lim}, journal={SIAM J. Matrix Anal. Appl.}, year={2006}, volume={30}, pages={1084-1127} }

There has been continued interest in seeking a theorem describing optimal low-rank approximations to tensors of order 3 or higher that parallels the Eckart-Young theorem for matrices. In this paper, we argue that the naive approach to this problem is doomed to failure because, unlike matrices, tensors of order 3 or higher can fail to have best rank-$r$ approximations. The phenomenon is much more widespread than one might suspect: examples of this failure can be constructed over a wide range of…

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