Symmetries in language statistics shape the geometry of model representations

Although learned representations underlie neural networks' success, their fundamental properties remain poorly understood. A striking example is the emergence of simple geometric structures in LLM representations: for example, calendar months organize into a circle, years form a one-dimensional manifold, and the latitude and longitude of cities can be decoded by low-dimensional linear probes. We show that the statistics of language exhibit a translation symmetry---e.g,. the co-occurrence probability of two months depends only on the time interval between them---and we prove that the latter governs the aforementioned geometric structures in high-dimensional word embedding models. Moreover, we find that these structures persist even when the co-occurrence statistics are strongly perturbed (for example, by removing all sentences in which two months appear together) and at moderate embedding dimension. We show that this robustness naturally emerges if the co-occurrence statistics are collectively controlled by an underlying continuous latent variable. We empirically validate this theoretical framework in word embedding models, text embedding models, and large language models.