arXiv Machine Learning By Farhad Pashakhanloo, Jacob A. Zavatone-Veth

Broken scale symmetries in undercomplete linear autoencoders

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The paper investigates how finite‑stepsize stochastic gradient descent (SGD) breaks scale symmetry in undercomplete linear autoencoders. It shows that SGD induces a directed scale drift that favors large decoder weights on the PCA solution manifold, a process that is slow and analytically tractable but eventually halted by a stability boundary. The resulting solutions exhibit sharper loss Hessians compared to a balanced baseline, illustrating how loss geometry can transform residual gradient noise into directed motion along equivalent solution manifolds.

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