DySem: Uncovering Dynamic Semantic Components of Large Language Models for Calculating Semantic Textual Similarity

Kaijie Zheng, Weiqin Wang, Yile Wang, Hui Huang


Abstract
Calculating semantic textual similarity is a foundational task in natural language processing. Current large language models (LLMs) based methods typically rely on extracting last-layer hidden states with fixed dimensions to compute similarity for every text pairs. We argue that this paradigm is suffer from two limitations: (i) The last hidden layer encodes more general knowledge rather than just semantic knowledge, making it suboptimal for semantic similarity computation; (ii) The hidden layer dimensions of LLMs are generally very large, which introduces some redundancy and noise for representing semantics. In this work, we propose DySem, a novel training-free framework that investigates more semantic-related internal components of LLMs via multilingual consensus, and shifts away from static representation spaces in favor of dynamic, sample-specific semantic dimensions by constructing text-dependent joint semantic set and computes similarity over this shared dimensional subset. Extensive experiments across various LLMs show that our method consistently outperforms recent baselines while maintaining lower dimensions for similarity calculation.
Anthology ID:
2026.emnlp-main.2596
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
58948–58967
Language:
URL:
https://aclanthology.org/2026.emnlp-main.2596/
DOI:
Bibkey:
Cite (ACL):
Kaijie Zheng, Weiqin Wang, Yile Wang, and Hui Huang. 2026. DySem: Uncovering Dynamic Semantic Components of Large Language Models for Calculating Semantic Textual Similarity. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 58948–58967, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
DySem: Uncovering Dynamic Semantic Components of Large Language Models for Calculating Semantic Textual Similarity (Zheng et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.2596.pdf