Lost in Specialization: Embedding Geometry and Retrieval Quality Across Specialized Corpora

Cornelia Ferner, Stefan Wegenkittl


Abstract
Reliably operating LLMs in specialized domains often requires retrieval-augmented generation (RAG), which grounds the model’s responses in domain-specific information. Retrieval performance is critical for output quality, making retrieval model selection a key decision for specialized RAG deployments. To guide retrieval model selection, we ask whether domain-tuned encoders produce better-structured embedding spaces for specialized corpora than general-purpose encoders, and whether geometric regularity alone reliably indicates retrieval quality in these settings. Our results show that the answer is more nuanced than expected: domain-specific models show more pronounced geometric irregularity than general-domain encoders, while geometric regularity alone does not reliably indicate retrieval quality. Moreover, geometric and intervention patterns observed on MS-MARCO do not consistently transfer to specialized corpora.
Anthology ID:
2026.blackboxnlp-1.4
Volume:
Proceedings of the 9th BlackboxNLP Workshop: Analyzing and Interpreting Neural Networks for NLP
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Dana Arad, Yonatan Belinkov, Hanjie Chen, Nils Feldhus, Aaron Mueller, Hosein Mohebbi, Gabriele Sarti, Martin Tutek
Venues:
BlackboxNLP | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
49–57
Language:
URL:
https://aclanthology.org/2026.blackboxnlp-1.4/
DOI:
Bibkey:
Cite (ACL):
Cornelia Ferner and Stefan Wegenkittl. 2026. Lost in Specialization: Embedding Geometry and Retrieval Quality Across Specialized Corpora. In Proceedings of the 9th BlackboxNLP Workshop: Analyzing and Interpreting Neural Networks for NLP, pages 49–57, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Lost in Specialization: Embedding Geometry and Retrieval Quality Across Specialized Corpora (Ferner & Wegenkittl, BlackboxNLP 2026)
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PDF:
https://aclanthology.org/2026.blackboxnlp-1.4.pdf