Unverified 2026

Denjoy Affine-Orbit Memory

Implementation & benchmark of arXiv:2607.11748 — Denjoy examples of class $C^1$ with affine dynamics outside the invariant Cantor set

Usefulness5/10
Difficulty6/10
Novelty8/10

Source paper: Denjoy examples of class $C^1$ with affine dynamics outside the invariant Cantor set arXiv:2607.11748 ⓘ · analyzed Aug 30, 2026

AI-generated research hypothesis, automatically tested. Not peer-reviewed.

Idea description

Add a bounded phase variable and a bank of local affine transport maps to an RNN or state-space model. The phase follows an irrational rotation, while the hidden state is transported through cells whose widths determine local gains, giving a controllable memory mechanism with analytically known distortion rather than an unconstrained recurrent Jacobian.

Formulas

L = Σₙ∈ℤ lₙ < ∞, xₙ = {nα}, α ∉ ℚ
p(t) = sup{x ∈ [0,1): Σ_{n: {nα} ∈ [0,x)} lₙ ≤ t}, p(Iₙ) = xₙ
F(z) = aₙ₊₁ + (lₙ₊₁/lₙ)(z − aₙ), z ∈ Iₙ = [aₙ, aₙ + lₙ]
Πₖ₌₀ᵐ⁻¹ (lₙ₊ₖ₊₁/lₙ₊ₖ) = lₙ₊ₘ/lₙ

Mathematical statement

The construction replaces the rotation-orbit point xₙ = {nα} by an interval Iₙ of length lₙ > 0, where α is irrational and L = Σₙ lₙ is finite. The lifted map sends Iₙ to Iₙ₊₁. Let Iₙ = [aₙ, aₙ + lₙ] and define the affine phase map F(z) = aₙ₊₁ + sₙ(z − aₙ), with slope sₙ = lₙ₊₁/lₙ. For a payload state h in Rᵈ, use a cell-dependent affine update h⁺ = Aₙh + bₙ. The phase update is θ⁺ = θ + α modulo 1, and a lookup maps θ to the active cell. The key identity is that the product of phase slopes over m steps telescopes: Πₖ₌₀ᵐ⁻¹ sₙ₊ₖ = lₙ₊ₘ/lₙ. Therefore, long-horizon phase transport has no hidden gain beyond the ratio of endpoint widths. Equal widths produce unit slopes, while bounded width ratios produce bounded phase distortion.

Implementation notes

1. Integration point: implement this as a recurrent memory branch alongside a GRU, vanilla RNN, or state-space model. Maintain a scalar phase θₜ and update θₜ₊₁ = (θₜ + α) mod 1. Use either a differentiable soft assignment over N cells or a hard nearest-cell assignment. Each cell stores an affine payload map Aₙh + bₙ, and its output is combined with the main network through a learned gate. For a finite prototype, choose N cells and α = √2 − 1 modulo 1; use periodic indexing n mod N. 2. Pseudocode: parameterize positive widths as lₙ = softplus(uₙ) + ε, normalize them, compute sₙ = lₙ₊₁/lₙ, identify the active cell n from θₜ, update the phase coordinate zₜ₊₁ = aₙ₊₁ + sₙ(zₜ − aₙ), update the payload hₜ₊₁ = Aₙhₜ + bₙ, and advance θ. Add λ Σₙ(log sₙ)² if bounded distortion is desired. 3. Computed directly: widths, local slopes, total width, and telescoping endpoint ratios. Estimated empirically: task loss, gradient norms, payload Jacobian products, and delayed-retrieval accuracy. 4. First cheap experiment: compare this module with a matched-parameter GRU on sequential MNIST and a delayed-copy task with delays from 10 to 10,000. Test uniform widths, fixed nonuniform widths, and learned widths. The falsifiable prediction is that the measured product of phase slopes after m steps equals lₙ₊ₘ/lₙ within 1% away from lookup boundaries. In the finite N-cell version, the phase product after exactly N steps must equal 1. Phase instability should appear only when the payload Jacobian product exceeds 1, not merely from iterating the phase branch.

Verification

This idea has not been verified yet.

Verification happens in two stages: Stage 1 — a mechanism check on a toy system confirms the claimed mathematical phenomenon reproduces; Stage 2 — a benchmark implements the idea on a real (small) neural network task and compares it against a tuned baseline over 8 paired seeds with a permutation test.

Artifacts

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