The Geometric Whitney Problem and Approximations by Neural Networks on Manifolds

Abstract Why do neural networks overcome the curse of dimensionality? A common justification is that real-life high-dimensional data typically lie close to low-dimensional manifolds, and that neural networks can exploit this structure efficiently – overcoming the curse of dimensionality for their parameter counts. However, existing bounds depend on properties of the manifolds that cannot be read off from data alone. We close this gap. If a dataset locally looks like a low-dimensional linear space – a condition testable directly from data and derivable from the empirically supported manifold hypothesis under well-behaved conditions – then an approximating manifold M can be constructed. Neural networks can then approximate C 1 functions uniformly on M , with parameter counts bounded purely in terms of computable properties of the data and overcoming the curse of dimensionality.