arXiv Machine Learning

Quantifying Concentration Phenomena of Mean-Field Transformers in the Low-Temperature Regime

arXiv:2605. 10931v2 Announce Type: replace-cross Abstract: Transformers with self-attention modules as their core components have become an integral architecture in modern large language and foundation models.

arXiv Machine Learning
Oct 22

Kinetic theory for Transformers and the lost-in-the-middle phenomenon

The paper investigates causal self‑attention dynamics in decoder Transformers, modeling them as a non‑exchangeable interacting particle system. Using cumulant expansions and Glauber calculus, the authors prove a quantitative mean‑field limit and a next‑order correlation characterization. For i.i.d. uniformly distributed tokens, they solve the limiting correlation equation in closed form and rigorously explain the empirically observed lost‑in‑the‑middle phenomenon, showing a U‑shaped token retrieval profile with primacy, recency, and a unique interior minimum under a smallness condition.

By Mitia Duerinckx, Borjan Geshkovski, Stefano Rossi
arXiv Statistics ML
Oct 23

SympFormer: Inertial Attention Blocks from Damped Hamiltonian Dynamics on Spaces of Probability Measures

The paper introduces SympFormer, a framework that derives accelerated attention blocks from inertial, Nesterov-type damped Hamiltonian dynamics on spaces of probability densities. It develops new geometries—local-mobility for Otto-Wasserstein and softmax-Wasserstein, and a quotient Stein geometry—to rigorously formulate these dynamics, providing gradient-flow and Hamiltonian foundations for softmax and linear attention. The authors analyze existence conditions, link continuous moment blow-up to discrete layer depth, and propose geometric corrections that empirically improve next-token prediction in decoder-only models.

By Viktor Stein, Levin Maier, Wuchen Li, Gabriele Steidl
arXiv Machine Learning
Jun 9

Token Sample Complexity of Attention

arXiv:2512. 10656v3 Announce Type: replace Abstract: As context windows in large language models continue to expand, it is essential to characterize how attention behaves at extreme sequence lengths.

By L\'ea Bohbot, Cyril Letrouit, Gabriel Peyr\'e, Fran\c{c}ois-Xavier Vialard
arXiv Machine Learning
Oct 15

From Global to Tail Convergence: Dynamics of $\alpha$-Stable Score-Based Generative Models

arXiv:2610. 19773v1 Announce Type: new Abstract: Score-based generative models driven by $\alpha$-stable L{\'e}vy processes have been proposed as an alternative to Brownian diffusion models, with empirical evidence suggesting improved sampling and better modeling of heavy-tailed data.

By Ianis Hammani (ENS Paris Saclay, LMO), Claire Boyer (LMO, IUF)
arXiv AI
Sep 17

The Attention Within: Consensus Dynamics in Selective State Space Models

Selective state space models (SSMs) use a recurrence to mix token information, a process analogous to attention in transformers. By modeling token evolution as an ordinary differential equation and applying input‑to‑state stability, the study proves that SSMs exhibit local exponential stability of consensus equilibria and delineates their domain of attraction for time‑varying weight matrices. Experiments on a pretrained Mamba‑2 model reveal that the output gate controls the degree of consensus, preventing tokens from fully converging.

By Jo\~ao Pedro Silvestre, \'Alvaro Rodr\'iguez Abella, Paulo Tabuada