Mid-training bifurcation: fractal basins emerge as a transformer learns to generalize

wgilpin0 · x · 2026-09-09

The authors demonstrate fractal basin formation by training a loop transformer to solve integer linear regression. A bifurcation occurs mid-training: the transformer figures out how to solve unseen examples, and fractal basins appear at the same time — direct training-dynamics evidence that fractal structure co-emerges with generalization.

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