Pointers

Brazil – China (Mainland, Macau) – Portugal · UFRN · 6–7 August 2026

Five talks on this two-day programme sit directly on top of open questions in the dm³ work. Two of them — Landim and Faria — are closer to it than anything on the Bienal programme.

Interacting particle systems and the n-bonacci chains

Claudio Landim · IMPA
Thursday 6 Aug · 15:10 · Plenary Talk 6

The DNLS work builds discrete nonlinear Schrödinger chains on tribonacci and tetrabonacci substitution sequences, and measures a localisation transition by finite-size scaling — IPR against λ, α against N, saturation times against N. The whole apparatus is empirical: run the chain, fit the exponent.

Ask: hydrodynamic-limit methods exist precisely to turn that kind of empirical scaling into a theorem about the limiting object. Is a substitution-sequence chain tractable in that framework, or does aperiodicity destroy the scaling limit?

Stability, delay, and the asymmetric basin

Teresa Faria · Universidade de Lisboa
Friday 7 Aug · 14:30 · Plenary Talk 10

The dm³ inner boundary fails at r★ = 0.77594059 rather than at Grönwall's 2/3 because the coupling term 2(r−1)e⁻ᶻ is sign-aware: it behaves differently above and below r = 1. A symmetric Lyapunov argument cannot see that.

Ask: stability theory for delay and functional equations routinely builds Lyapunov functionals with asymmetric structure. Is there a construction that gives the sharp one-sided bound directly — the thing a symmetric ball provably cannot deliver?

Ricci flow and the curvature operator

Gang Tian · Peking University
Thursday 6 Aug · 17:40 · Plenary Talk 9

The operator chain G = U ∘ F ∘ K ∘ C treats K as curvature: the stage that constrains which configurations remain available, with a verified bound κ* ≤ √(7/9) ≈ 0.882. The framework's claim is that curvature removes options rather than supplying a drive — form is what the constraints permit.

Ask: Ricci flow is the canonical statement that curvature evolves geometry under a rule. Is there any sense in which κ* is a flow-invariant threshold, or is the correspondence purely nominal? This is the bridge most likely to turn out to be a metaphor, and the one worth checking hardest.

Continued fractions, again — and a second chance

Carlos Gustavo Moreira (Gugu) · IMPA
Thursday 6 Aug · 14:30 · Plenary Talk 5  — also Bienal, Wednesday 09:00

He speaks at both conferences. The tribonacci constant η ≈ 1.8393 anchors the criticality threshold in the DNLS chapter; whether that threshold is really a statement about rational approximation is the sharpest open question in the series.

Ask: the smaller room on Thursday is the better one. Same question as the Bienal, asked with more time.

Algebra and the operator chain

Vyacheslav Futorny · SUSTech
Friday 7 Aug · 15:10 · Plenary Talk 11

Volume I is an operator algebra: g-, L-, R- and U-operator families, a compositional grammar, and a claim that G applied to itself has a fixed point. It was written by someone doing dynamics, not representation theory.

Ask: does the operator grammar have an actual algebraic structure — is it a known category of algebras wearing unfamiliar notation? Being told "this is already a thing and it is called X" would be the most useful outcome of the week.

Numerics

Jinyun Yuan · Plenary Talk 12  ·  Changfeng Gui · Plenary Talk 13
Friday 7 Aug · 15:50 and 17:00

Everything sharp in this project rests on DOP853 integration at high precision, and everything symmetric rests on a PDE-style estimate that turns out to be blunt. Those are the two talks where the numerical-analysis and symmetry-breaking questions live respectively.

Ask (Yuan): what does it take for a numerical basin certificate to be publishable as a certificate rather than an illustration? Ask (Gui): symmetry-breaking in PDE has a mature toolkit — does any of it apply to an ODE whose basin breaks symmetry the same way?

What is not claimed

dm³ is a toy system. It has an explicit closed form, one attracting limit cycle, and a basin whose inner edge has been located numerically to eight digits and not proved. The Lean development verifies the surrounding structure — eigenvalue, τ = 2, ε₀ = 1/3, the singularity classification — and states the basin result only as an existence claim over the interval (2/3, 1), which is far weaker than the number suggests. Nothing here needs to be taken on faith: the integrator, the Lean files and the failing cases are all public.