Unverified
2026
Normal Spectral Linear Layer
Replace an unconstrained dense transition or recurrent matrix with a normal matrix $A=U\operatorname{diag}(\lambda)U^*$, where $U$ is unitary and $\lambda$ contains learnable eigenvalues. The layer can be initialized by fitting a normal matrix to input-output pairs through the paper's objective, then trained with Riemannian updates that keep $U$ unitary and preserve the normal-operator structure.
Paper: The Normal Procrustes Problem: A Riemannian Optimization Approach
arXiv:2608.19513