Unlearning Isn't Deletion: Investigating Reversibility of Machine Unlearning in LLMs

In three linesStudy showing that unlearning in LLMs merely suppresses information at surface level—models recover original behavior through minimal fine-tuning. Authors introduce representation-level analysis framework (PCA, CKA, Fisher information) to assess genuine data erasure and identify four forgetting regimes based on reversibility and catastrophicity.

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