Positive Semidefinite Supermartingales and Randomized Matrix Concentration Inequalities

• URL: http://arxiv.org/abs/2401.15567v3
• Date: Mon, 26 Feb 2024 05:12:46 GMT
• Title: Positive Semidefinite Supermartingales and Randomized Matrix Concentration Inequalities
• Authors: Hongjian Wang, Aaditya Ramdas
• Abstract summary: We present new concentration inequalities for either martingale dependent or exchangeable random symmetric matrices under a variety of tail conditions. These inequalities are often randomized in a way that renders them strictly tighter than existing deterministic results in the literature.
• Score: 35.61651875507142
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: We present new concentration inequalities for either martingale dependent or exchangeable random symmetric matrices under a variety of tail conditions, encompassing now-standard Chernoff bounds to self-normalized heavy-tailed settings. These inequalities are often randomized in a way that renders them strictly tighter than existing deterministic results in the literature, are typically expressed in the Loewner order, and are sometimes valid at arbitrary data-dependent stopping times. Along the way, we explore the theory of positive semidefinite supermartingales and maximal inequalities, a natural matrix analog of scalar nonnegative supermartingales that is potentially of independent interest.

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