Shape of Memory: a Geometric Analysis of Machine Unlearning in Second-Order Optimizers

Fuente: arXiv
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Main Author: Stewart, Kennon
Format: Preprint
Published: 2026
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author Stewart, Kennon
author_facet Stewart, Kennon
contents We argue that current definitions of machine unlearning are underspecified for second-order optimizers. We compare first-order and second-order learners for their ability to handle the data deletion task with varying degrees of eigendecomposition to mimic the loss model memory. While both first and second-order methods realign with the ideal counterfactul in terms of performance and gradient, the second-order optimizer shows significant volatility in the optimizer state. This indicates residual information, supposedly deleted, that isn't detectable by first-order analysis. Various eigendecay treatments show that stability and information loss is regained only under controlled state pertubation where geometric information (or memory) is erased.
format Preprint
id arxiv_https___arxiv_org_abs_2604_23046
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Shape of Memory: a Geometric Analysis of Machine Unlearning in Second-Order Optimizers
Stewart, Kennon
Machine Learning
Information Theory
Social and Information Networks
We argue that current definitions of machine unlearning are underspecified for second-order optimizers. We compare first-order and second-order learners for their ability to handle the data deletion task with varying degrees of eigendecomposition to mimic the loss model memory. While both first and second-order methods realign with the ideal counterfactul in terms of performance and gradient, the second-order optimizer shows significant volatility in the optimizer state. This indicates residual information, supposedly deleted, that isn't detectable by first-order analysis. Various eigendecay treatments show that stability and information loss is regained only under controlled state pertubation where geometric information (or memory) is erased.
title Shape of Memory: a Geometric Analysis of Machine Unlearning in Second-Order Optimizers
topic Machine Learning
Information Theory
Social and Information Networks
url https://arxiv.org/abs/2604.23046