Predicting Emerging Topics from Outliers: A Prospective Study of Weak Signals in Embedding Space

Evangelia Zve, Gauvain Bourgne, Jean-Gabriel Ganascia


Abstract
Some documents that embedding-based topic models initially classify as noise later become founding members of emerging topics. At publication time, however, they appear as scattered points in embedding space and are difficult to distinguish from ordinary noise without the benefit of hindsight. We study whether such *anticipatory outliers* can be predicted prospectively, using only information available when a document first appears. We derive labels from the subsequent trajectories of outlier documents, distinguishing those that anticipate new topics from those that reinforce existing topics or remain isolated, and estimate label confidence through agreement across multiple embedding models. On two French news corpora, anticipatory outliers prove predictable at publication time. Under cross-validation, F1 rises from about 0.77 over the full eligible population to above 0.90 on high-consensus subsets, and remains at 0.76–0.80 under a strictly chronological evaluation. Predictive performance is driven mainly by geometric features capturing each outlier’s position in embedding space.
Anthology ID:
2026.findings-aacl.94
Volume:
Findings of the Association for Computational Linguistics: IJCNLP-AACL 2026
Month:
November
Year:
2026
Address:
Hengqin, China
Editors:
Yue Zhang, Ruifeng Xu, Ayu Purwarianti, Tong Rong, Jun Suzuki
Venue:
Findings
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
1898–1913
Language:
URL:
https://aclanthology.org/2026.findings-aacl.94/
DOI:
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Cite (ACL):
Evangelia Zve, Gauvain Bourgne, and Jean-Gabriel Ganascia. 2026. Predicting Emerging Topics from Outliers: A Prospective Study of Weak Signals in Embedding Space. In Findings of the Association for Computational Linguistics: IJCNLP-AACL 2026, pages 1898–1913, Hengqin, China. Association for Computational Linguistics.
Cite (Informal):
Predicting Emerging Topics from Outliers: A Prospective Study of Weak Signals in Embedding Space (Zve et al., Findings 2026)
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https://aclanthology.org/2026.findings-aacl.94.pdf