Machine-learning ideas tagged Functional analysis in the Math taxonomy of the Math2NN corpus.
Replace a fixed-norm Fourier feature layer by a Fourier transform followed by spatially varying modular normalization. Use a baseline exponent approaching the endpoint regime at large coordinates and permit only bounded, smooth deviations so the transform remains controlled while the network can emphasize localized details.
Replace an isotropic Fourier-feature map with a fractional low-pass map whose order is selected from the estimated intrinsic Frostman dimension of the training samples. The layer represents a coefficient vector f in the ambient domain, applies the multiplier |k|^{-s}, and evaluates the smoothed function on the observed fractal-like data support. The theorem provides a geometry-dependent bound preventing high-frequency coefficient energy from producing arbitrarily large responses on concentrated…
Construct a recurrent or state-space block with two learned transition matrices A and B representing two commuting update directions. Besides penalizing noncommutation and deviation from isometry, penalize the negative spectrum of the paper's core operator H(A,B), encouraging a structured overlap of one-step and two-step ranges. Compare this against an orthogonal-RNN baseline and against commutation-only regularization on long-horizon sequence tasks.
For a learned phase-space layer, estimate its symplectic Fourier bandwidth R and divide its output gain by the theorem's support-dependent factor R raised to an exponent determined by the Schatten index p. This creates a resolution-aware normalization: layers with larger phase-space bandwidth are automatically damped when p is not equal to 2, while the Hilbert-Schmidt case p = 2 remains unscaled.
Add a loss that prevents an intermediate feature map from being simultaneously concentrated inside a porous spatial region and a porous frequency region. The regularizer is based on the fractal uncertainty inequality: if frequency support is restricted to a porous set Y, then the fraction of feature energy inside a porous spatial set X is at most C h^beta; violations of this bound are penalized.
Use the derivative of fractional feature energy with respect to its order as a regularizer for intermediate representations. This penalizes unstable scale behavior rather than simply suppressing all high frequencies, so it can preserve useful detail while discouraging uncontrolled changes across spatial scales.
Replace or augment relative-position attention with a positive fractional-integration mixing kernel whose radial behavior has separate inner and outer power laws. Tokens close to one another interact through the usual fractional singularity, while tokens near different radial scales receive a ground-state correction that can improve multiscale information transport without introducing a dense learned positional table.
Represent tokens, features, or attention states by normalized rank-one matrices and train the network to preserve their Schatten-p distance profiles over complex phase rotations. Because the paper proves that equality of all distances \(\|\lambda e-v\|_p\) identifies \({\rm Tr}(e^*v)\), this regularizer preserves matrix overlap geometry under a learned transformation.
Treat the learned latent transition F_theta as a homeomorphism-like operator and monitor the range of its temporal-difference operator D_theta u = u composed with F_theta minus u. If the smallest nontrivial singular values of the sampled operator collapse toward zero as trajectory length or basis size grows, the latent dynamics are entering an ill-conditioned coboundary regime. Use this signal to reduce the recurrent step size, impose contraction, or replace the transition by a periodicized…
Insert a magnitude-only bottleneck whose output is the absolute value of a random independent-feature expansion of the latent vector. Train a decoder to reconstruct the latent representation or input modulo one global sign, while explicitly rejecting feature distributions whose normalized L1 mass is too small. The module provides a controlled way to obtain sign-invariant representations without allowing arbitrary coordinate-wise sign loss.
Replace the usual squared input-Jacobian penalty with a stochastic approximation of the affine Sobolev energy, which computes an inverse-power spherical average of directional derivative norms. The negative exponent emphasizes directions with unusually small sensitivity and prevents the regularizer from being represented only by the largest-gradient direction.
Apply the paper's reversed weighted interaction inequality to two nonnegative feature maps generated from different augmentations or network branches. Maximizing the normalized nonlocal interaction should discourage collapsed or overly concentrated spatial representations while remaining invariant to overall feature amplitude.
Add a differentiable rearrangement-envelope penalty to a positive integral-kernel layer. The penalty uses the Laplace-transform inequality to prevent the sorted upper tail of the layer output from becoming substantially larger than the cumulative upper tail of its input, providing a distribution-sensitive alternative to ordinary activation clipping or an L2 penalty.
Train a neural function under hard pointwise constraints by projecting its desired output-space update into the Clarke tangent cone of the admissible set at every sampled input. Fit the resulting feasible measurable direction with a parameter update instead of repeatedly allowing the network to violate constraints and repairing it with a penalty.
Represent the prediction as a sum of a smooth interior branch and a fractional boundary branch: u_theta(x)=u_int_theta(x)+d(x)^a u_bd_theta(x). This mirrors the paper's direct-sum solution structure and allocates separate network capacity to the globally regular component and the boundary layer.
Parameterize candidate eigenfunctions with a neural network, project them into a finite spectral trial space, and compute Ritz eigenvalues from the resulting Galerkin matrices. Train against the paper's rigorous lower-bound transform rather than trusting the raw Ritz values, producing a certificate that the predicted eigenvalues do not underestimate the exact eigenvalues under the projection-error assumptions.
Add a boundary-aware nonlocal regularizer to hidden-state sequences by subtracting the sharp Hardy weight from the fractional discrete-Laplacian energy. The resulting penalty is provably nonnegative on finite sequences under zero-padding at the left boundary, while its position-dependent Gamma-ratio weight concentrates protection near the sequence boundary.
Add an inverse-capacitary-distance penalty to coordinate-network outputs near complex forbidden sets, rather than using only Euclidean distance-to-boundary weighting. The penalty is theoretically compatible with the network's spatial Dirichlet energy: it suppresses large values near obstacles while the gradient penalty controls the weighted singularity, even when the obstacle is thin, perforated, or fractal-like.
Parameterize a complex neural feature F(z) as a low-degree holomorphic polynomial and train it from magnitude-squared observations using a Gaussian-weighted residual to the best constant intensity baseline. The paper's coercivity inequality makes this more than an observation-space loss: small intensity variation certifiably bounds the error of the phase-invariant squared feature F^2-F(0)^2. Use the bound as a regularizer or as a replacement for an unavailable complex-target loss in…
Replace ordinary summation of several matrix-valued residual branches by a concave spectral aggregation: form the branch sum, take its absolute value, and apply a nonnegative concave function to singular values. The paper's transfer theorem predicts that the sharp Schatten-norm amplification constant is no worse than the corresponding linear Lee-type constant, while square-root, logarithmic, and capped maps suppress dominant singular directions.
Replace an unconstrained bilinear feature interaction with a joint spectral filter that only allows pairs of graph or spherical frequencies satisfying a soft radius constraint. The smooth factor attenuates interactions near and beyond the cutoff instead of making the hard low-pass decision used by ordinary spectral truncation, which should reduce high-frequency aliasing and unstable feature products.
Treat repeated residual blocks as an infinite directed transition system, damp transitions according to their depth, and regularize a finite part of the resulting Fredholm log-determinant. Subtracting a dilogarithmic counterterm prevents the regularizer from being dominated by infinitely repeated short cycles, while retaining information about global recurrent amplification.
Apply the sharp lattice Hardy inequality to intermediate feature maps defined on a 3D voxel grid. Penalize feature configurations whose inverse-square-weighted energy around a designated anchor is too large relative to their nearest-neighbor gradient energy, discouraging isolated activation spikes near the anchor while retaining smooth spatial structure.
Equip a learned embedding with a pullback Riemannian metric and regularize the bottom eigenvalue of the operator -Δ_g+γ scal_g. The regularizer searches for localized functions with low Dirichlet energy plus curvature potential, thereby penalizing unstable regions that ordinary Jacobian-norm penalties may miss.