A zero-entropy system without a smooth positive-volume modelOpen Problem
Motivation
A measure-preserving system may have low information production yet fail to admit a smooth realization. The target asks for a single ergodic system excluding every finite-dimensional smooth positive-volume model. The source manuscript presents the surrounding research claim.
Setting
The system is a measurable equivalence T of a standard nonatomic probability space. Standard nonatomic is expressed by an isomorphism with the unit interval after removing null sets. A smooth model is a compact smooth manifold, a smooth diffeomorphism and an invariant probability measure with strictly positive smooth local coordinate density.
Formalization target
Construct a system satisfying
The formal finite-entropy predicate requires every finite-partition entropy rate to converge, with one finite real upper bound.
The selected formal target is OAI.SmoothObstruction.main.
Significance and status
The obstruction ranges over every finite dimension, nonorientable manifolds and positive-dimensional smooth boundary models. The manuscript asserts zero entropy; the selected published theorem requires finite entropy only. The published target is currently Open; the manuscript's argument and a checked Lean proof are separate deliverables.
Difficulty
Failure of a particular embedding does not exclude all measure-theoretic conjugacies and all dimensions. Conjugacy is allowed after discarding invariant null sets.
Formalization scope
The goal quantifies over measurable equivalences and uses conull measurable conjugacy, not topological conjugacy. Entropy is measured in bits by the supplied finite-partition definition. Closed models include dimension zero, boundary models require positive dimension, and no orientation hypothesis is imposed.
Selected references
- OpenAI, A zero-entropy system without a smooth positive-volume model, preprint, 2026. Pinned manuscript.
- OpenAI, accompanying formal statements, commit
adc7f1241b42. Goal source.