Bregman meets Lévy: Stochastic mirror descent with heavy-tailed noise in continuous and discrete time
- URL: http://arxiv.org/abs/2606.03769v1
- Date: Tue, 02 Jun 2026 15:23:04 GMT
- Title: Bregman meets Lévy: Stochastic mirror descent with heavy-tailed noise in continuous and discrete time
- Abstract summary: We study the robustness of mirror descent (SMD) under heavy-tailed noise.<n>We show that the Lévy mirror flow (LMF) attains $$optimality within $mathcalO(-p/(p-1))$ time.
- Score: 20.88662531990403
- License: http://creativecommons.org/licenses/by/4.0/
- Abstract: We study the robustness of stochastic mirror descent (SMD) under heavy-tailed noise, focusing on whether the method retains its convergence guarantees when run with infinite-variance stochastic gradient input. To address this question in a principled manner, we begin by introducing a continuous-time model of SMD as a stochastic differential equation (SDE) driven by a centered Lévy noise process with finite $p$-th order moments, $1 < p \leq 2$. This scheme -- which we call the Lévy mirror flow (LMF) -- arises naturally as the scaling limit of SMD in the presence of heavy-tailed noise. In particular, when $p < 2$ -- the heavy noise regime -- the trajectories of LMF generically exhibit jump discontinuities of arbitrary magnitude which, if frequent enough, lead to infinite variance. Nonetheless, despite this highly singular behavior, we show that LMF attains $ε$-optimality within $\mathcal{O}(ε^{-p/(p-1)})$ time in the convex case, and within $\mathcal{\tilde O}(ε^{-1/(p-1)})$ time for (relatively) strongly convex objectives. These guarantees provide a transparent characterization of the impact of frequent long jumps on the convergence of the process, and percolate to a series of matching discrete-time guarantees for several variants of SMD under heavy-tailed noise.
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