Follow the Geometry, Not the Model: Cold Start Semi-Supervised Learning
- URL: http://arxiv.org/abs/2609.14451v1
- Date: Sun, 13 Sep 2026 11:46:26 GMT
- Title: Follow the Geometry, Not the Model: Cold Start Semi-Supervised Learning
- Abstract summary: We propose VAST (Veracity-Aware Semi-Supervised Training), which decouples pseudo-label generation and training.<n>VAST outperforms the strongest graph-based SSL baselines at every operating point across three datasets.
- Score: 7.6344611819427035
- License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
- Abstract: Modern semi-supervised learning (SSL) couples pseudo-label generation and classifier training, using the classifier's own confidence to select the pseudo-labels that are then used to update the model. In the cold-start regime, where at most a few labels per class are available, this coupling is ill-posed, since the classifier cannot supervise itself before it has learned. To address this problem, we propose VAST (Veracity-Aware Semi-Supervised Training), which decouples these two stages. Probabilistic beliefs over the unlabeled set are first inferred directly from the geometry of a frozen self-supervised embedding and only then distilled into an inductive classifier. The construction rests on the Veracity Matrix, a kernel-based structure that aggregates label evidence across the data manifold and admits an interpretation as a Dirichlet posterior under a per-observation powered-likelihood model. Additionally, we introduce Veracity Propagation, a self-terminating belief-spreading step that extends coverage beyond the kernel neighborhood of the labeled set. Under a controlled protocol in which all methods receive identical frozen embeddings and labeled sets, VAST outperforms the strongest graph-based SSL baselines at every operating point across three datasets, with statistically significant gains in 7 of 9 comparisons, while producing a deployable inductive classifier rather than requiring transductive graph inference. Compared with end-to-end confidence-gated SSL, we further find that these methods underperform in this setting and, in our experiments, do not consistently exceed labeled-only performance.
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