arXiv AI By Vaibhav Prakash, Jayasri Dontabhaktuni

Phantom Transitions in Language Model Fine-Tuning: A Density-Matrix Analysis

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arXiv:2606. 07559v2 Announce Type: replace-cross Abstract: Fine-tuning a language model often fails silently when its correct completion must outrank a near-synonym competitor.

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arXiv Machine Learning
Sep 3

The Dynamics of Continuous Mixture Collapse in Language Models

The paper investigates why large language models (LLMs) fail to maintain continuous mixtures of token embeddings—used in latent-state reasoning—to preserve multiple reasoning paths. Through theory and experiments, it identifies three failure sources: transformer geometry distortion, amplification or contraction dynamics from softmax and autoregressive feedback, and the need for context-dependent corrections that scale with mixture size. Empirical results confirm the predicted transition between contraction and amplification and show pretrained models largely fall on the amplifying side.

By Ali Backour