Self-Attention as Transport: Limits of Symmetric Spectral Diagnostics
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Abstract (arXiv)
Every attention head defines a degree-normalized transport operator, and a growing family of diagnostics reads model behavior (hallucination among them) from its spectrum. We ask what such diagnostics can and cannot infer. The operator splits orthogonally into a symmetric part governing transport capacity and an antisymmetric part encoding orientation. We prove an identifiability limit: every transpose-invariant spectral diagnostic is orientation-blind (unable to distinguish an operator from its transpose, hence blind to the orientation of information flow), with a transpose-stability bound limiting any Lipschitz diagnostic's transpose sensitivity by the asymmetry coefficient G. This bounds what spectral diagnostics of the attention operator can resolve (e.g. LapEigvals and the attention-spectral branch of LLM-Check). On the surviving axis, a closed-form bipartite-Cheeger landscape shows uniform causal attention obeys an n-independent temporal-cut floor φ ≥ 1/5 while window attention pierces it as O(w/n); the floor is an idealized benchmark, not an empirical attractor, and the fraction of real heads falling below it is itself an empirically stable architectural descriptor. The two-axis diagnostic (φ for capacity, G for asymmetry magnitude) yields a falsifiable polarity prediction, borne out in sign under length-controlled, forced-scoring evaluation across decoder-only, encoder-only, and encoder--decoder models (capacity-axis signal 0.62--0.84 LC-AUROC): polarity reverses between HaluEval and MedHallu, directionally as predicted though asymmetric in strength, with decision polarity calibrated per regime.
Key facts. No citing papers in the map yet (data through 7 Oct 2026). Builds on 30 of its 57 references that are in the map. First posted on arXiv 6 May 2026.
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30 of 57 references.
References · 30
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- 2024INSIDE: LLMs' Internal States Retain the Power of Hallucination Detectioncited by 317
18 more
- 2023Stabilizing Transformer Training by Preventing Attention Entropy Collapsecited by 154
- 2024Long-form factuality in large language modelscited by 146
- 2024Lookback Lens: Detecting and Mitigating Contextual Hallucinations in Large Language Models Using Only Attention Mapscited by 140
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- 2023The emergence of clusters in self-attention dynamicscited by 133
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- 2022Cheeger Inequalities for Directed Graphs and Hypergraphs Using Reweighted Eigenvaluescited by 3
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