pith. sign in

arxiv: 2406.01123 · v2 · submitted 2024-06-03 · 🧮 math.DS

Ergodic optimization for continuous functions on non-Markov shifts

Pith reviewed 2026-05-24 00:34 UTC · model grok-4.3

classification 🧮 math.DS
keywords ergodic optimizationsubshiftsmaximizing measuresentropyintrinsically ergodicsymbolic dynamicsnon-Markov shifts
0
0 comments X

The pith

For intrinsically ergodic subshifts the continuous functions split into two classes with distinct properties for the entropy of their maximizing measures.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper shows that for a wide class of intrinsically ergodic subshifts over finite alphabets the space of continuous functions splits into two subsets. One is a dense Gδ set in which every maximizing measure has relatively small entropy. The other lies inside the closure of the functions that possess uncountably many fully supported ergodic maximizing measures of relatively large entropy. This unifies earlier findings and covers systems such as transitive piecewise monotonic maps, certain coded shifts and multidimensional β-transformations. A sympathetic reader cares because the split describes what happens for typical functions versus a dense collection of exceptional ones in ergodic optimization.

Core claim

For a wide class of intrinsically ergodic subshifts over a finite alphabet, the space of continuous functions on the shift space splits into two subsets: one is a Gδ dense set for which all maximizing measures have relatively small entropy; the other is contained in the closure of the set of functions having uncountably many, fully supported ergodic measures with relatively large entropy.

What carries the argument

The dichotomy that partitions the space of continuous functions into a dense Gδ set whose maximizing measures all have relatively small entropy and a complementary set whose closure contains functions with uncountably many large-entropy fully supported ergodic maximizers.

If this is right

  • The splitting holds for any transitive piecewise monotonic interval map.
  • The splitting holds for some coded shifts and multidimensional β-transformations.
  • The splitting holds for systems without Bowen's specification property.
  • There exist intrinsically ergodic subshifts that have positive obstruction entropy to specification.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The same partition may appear in optimization problems on other classes of dynamical systems once the intrinsic ergodicity condition is met.
  • One could test the boundary case by building a concrete subshift with controlled obstruction entropy and checking the entropy values numerically for sample functions.
  • The result supplies a template for classifying how many distinct ergodic measures can arise as maximizers when the underlying shift lacks specification.

Load-bearing premise

The subshifts under study are intrinsically ergodic over a finite alphabet.

What would settle it

Exhibit one intrinsically ergodic subshift over a finite alphabet together with a continuous function whose maximizing measures fall into neither of the two described classes.

read the original abstract

Ergodic optimization aims to describe dynamically invariant probability measures that maximize the integral of a given function. For a wide class of intrinsically ergodic subshifts over a finite alphabet, we show that the space of continuous functions on the shift space splits into two subsets: one is a $G_\delta$ dense set for which all maximizing measures have `relatively small' entropy; the other is contained in the closure of the set of functions having uncountably many, fully supported ergodic measures with `relatively large' entropy. This result considerably generalizes and unifies the results of Morris (2010) and Shinoda (2018), and applies to a wide class of intrinsically ergodic non-Markov symbolic dynamics without Bowen's specification property, including any transitive piecewise monotonic interval map, some coded shifts and multidimensional $\beta$-transformations. Along with these examples of application, we provide an example of an intrinsically ergodic subshift with positive obstruction entropy to specification.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 0 minor

Summary. The paper claims that for a wide class of intrinsically ergodic subshifts over a finite alphabet (including those without Bowen's specification property), the space of continuous functions splits into a Gδ-dense subset where all maximizing measures have 'relatively small' entropy, and a second subset contained in the closure of functions admitting uncountably many fully supported ergodic maximizing measures with 'relatively large' entropy. The result generalizes Morris (2010) and Shinoda (2018) and is applied to transitive piecewise monotonic interval maps, coded shifts, and multidimensional β-transformations; an example of an intrinsically ergodic subshift with positive obstruction entropy to specification is also given.

Significance. If the main dichotomy holds with the stated generality, the result would unify and extend the literature on generic properties of maximizing measures in ergodic optimization beyond Markov shifts and specification systems, providing a topological dichotomy in C(X) for a broad class of intrinsically ergodic symbolic systems. The applications to interval maps and other concrete examples would be a notable strength if the hypotheses are verified.

major comments (2)
  1. [Abstract / applications] Abstract and applications paragraph: the assertion that the result applies to 'any transitive piecewise monotonic interval map' is not supported, because there exist transitive piecewise monotonic maps that admit multiple distinct ergodic measures of maximal entropy and hence fail to be intrinsically ergodic; the main theorem's hypothesis is therefore not satisfied for those examples, so the claimed generality of the application does not hold.
  2. [Main theorem / Gδ-density argument] Main theorem statement and § on the Gδ-density argument: the definitions of 'relatively small' and 'relatively large' entropy are not supplied in the abstract and the verification of the Gδ-density construction is unavailable in the provided text; these are load-bearing for the claimed dichotomy and must be explicitly stated and proved before the result can be assessed.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the careful reading and for identifying these issues. We address each major comment below and will revise the manuscript accordingly.

read point-by-point responses
  1. Referee: [Abstract / applications] Abstract and applications paragraph: the assertion that the result applies to 'any transitive piecewise monotonic interval map' is not supported, because there exist transitive piecewise monotonic maps that admit multiple distinct ergodic measures of maximal entropy and hence fail to be intrinsically ergodic; the main theorem's hypothesis is therefore not satisfied for those examples, so the claimed generality of the application does not hold.

    Authors: We agree that the claim as stated is incorrect. Not every transitive piecewise monotonic interval map is intrinsically ergodic. We will revise the abstract and the applications paragraph to read 'any intrinsically ergodic transitive piecewise monotonic interval map' (and similarly qualify the statements for coded shifts and multidimensional β-transformations). revision: yes

  2. Referee: [Main theorem / Gδ-density argument] Main theorem statement and § on the Gδ-density argument: the definitions of 'relatively small' and 'relatively large' entropy are not supplied in the abstract and the verification of the Gδ-density construction is unavailable in the provided text; these are load-bearing for the claimed dichotomy and must be explicitly stated and proved before the result can be assessed.

    Authors: The notions of 'relatively small' and 'relatively large' entropy are defined immediately after the statement of the main theorem (Theorem 2.1) as entropy strictly less than, respectively strictly greater than, the entropy of the unique measure of maximal entropy. The Gδ-density construction and its verification appear in full in Section 3 (proof of Theorem 3.1). We will add a short parenthetical gloss of the two entropy notions to the abstract and ensure the complete proofs are visible in the version sent to the referee. revision: yes

Circularity Check

0 steps flagged

No circularity: pure existence theorem on intrinsically ergodic subshifts

full rationale

The paper is a self-contained existence result in ergodic theory. It proves a Gδ-density dichotomy for continuous functions on a class of subshifts defined by the external hypothesis of intrinsic ergodicity. The derivation generalizes Morris (2010) and Shinoda (2018) but does not reduce any claimed prediction or dichotomy to a fitted parameter, self-definition, or load-bearing self-citation chain. No equations or steps equate outputs to inputs by construction. The application statements invoke the hypothesis explicitly and do not manufacture circularity.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The result rests on the domain assumption that the subshifts are intrinsically ergodic; no free parameters or invented entities are introduced.

axioms (1)
  • domain assumption The subshifts are intrinsically ergodic over a finite alphabet
    Explicitly stated as the setting for the dichotomy in the abstract.

pith-pipeline@v0.9.0 · 5700 in / 1153 out tokens · 21039 ms · 2026-05-24T00:34:18.868343+00:00 · methodology

discussion (0)

Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.

Reference graph

Works this paper leans on

43 extracted references · 43 canonical work pages

  1. [1]

    A. T. Baraviera, R. Leplaideur and A. O. Lopes. Ergodic optimization, zero temperature limits and the max-plus algebra. IMPA Mathematical Publications, 29th Brazilian Mathematics Colloquium, Instituto Nacional de Matem´ atica Pura e Aplicada (IMPA ), Rio de Janeiro,

  2. [2]

    J. Bochi. Ergodic optimization of Birkhoff averages and Lyapunov exponents. Proceedings of the International Congress of Mathematicians , Rio de Janeiro, 2018. Vol. III. Invited lectures, 1825–1846, World Sci. Publ., Hackensack, NJ, 2018

  3. [3]

    T. Bousch. Le poisson n’a pas d’arˆ etes. Ann. Inst. Poincar´ e Probab. Statist.36 (2000), 489– 508

  4. [4]

    T. Bousch. La condition de Walters, Ann. Sci. de l’ ´Ecole normale sup. 34 (2001), 5988–6017. 26 MAO SHINODA, HIROKI TAKAHASI, KENICHIRO YAMAMOTO

  5. [5]

    Bousch and O

    T. Bousch and O. Jenkinson. Cohomology class of dynamically non- negative Ck functions. Invent. Math. 148 (2002), 207–217

  6. [6]

    R. Bowen. Entropy for group endomorphisms and homogeneous spaces, Trans. Amer. Math. Soc. 153 (1971), 401–414

  7. [7]

    Br´ emont

    J. Br´ emont. Entropy and maximizing measures of generic contin uous functions. C. R. Math. Acad. Sci. 346 (2008), 199–201

  8. [8]

    J. Buzzi. Specification on the interval. Trans. Amer. Math. Soc. 349 (1997), no.7, 2737–2754

  9. [9]

    J. Buzzi. Subshifts of quasi-finite type. Invent. Math. 159 (2005), 369–406

  10. [10]

    Climenhaga

    V. Climenhaga. Specification and towers in shift spaces. Commun. Math. Phys. 364 (2018), 441–504

  11. [11]

    Climenhaga and D

    V. Climenhaga and D. J. Thompson. Intrinsic ergodicity beyond s pecification: β-shifts, S-gap shifts, and their factors. Israel J. Math. 192 (2012), 785–817

  12. [12]

    Climenhaga and D

    V. Climenhaga and D. J. Thompson. Equilibrium states beyond spe cification and the Bowen property. J. Lond. Math. Soc. 87 (2013), 401–427

  13. [13]

    Climenhaga and D

    V. Climenhaga and D. J. Thompson. Intrinsic ergodicity via obstr uction entropies. Ergodic Theory Dyn. Syst. 34 (2014), 1816–1831

  14. [14]

    Climenhaga, D

    V. Climenhaga, D. J. Thompson and K. Yamamoto. Large deviatio ns for systems with non- uniform structure. Trans. Amer. Math. Soc. 369 (2017), 4167–4192

  15. [15]

    Contreras, A

    G. Contreras, A. O. Lopes and P. Thieullen. Lyapunov minimizing m easures for expanding maps of the circle. Ergod. Th. & Dynam. Sys. 21 (2001), 1379–1409

  16. [16]

    Hofbauer

    F. Hofbauer. On intrinsic ergodicity of piecewise monotonic tran sformations with positive entropy II. Israel J. Math. 38 (1981), 107–115

  17. [17]

    Hofbauer

    F. Hofbauer. Piecewise invertible dynamical systems. Probab. Theory Related Fields 72 (1986), 359–386

  18. [18]

    Hofbauer

    F. Hofbauer. Generic properties of invariant measures for sim ple piecewise monotonic trans- formations. Israel J. Math. 59 (1987), 64–80

  19. [19]

    Hofbauer

    F. Hofbauer. Generic properties of invariant measures for co ntinuous piecewise monotonic transformations. Monatsh. Math. 106 (1988), 301–312

  20. [20]

    Hofbauer and P

    F. Hofbauer and P. Raith. Density of periodic orbit measures fo r transformations on the interval with two monotonic pieces. Dedicated to the memory of Wies /suppress law Szlenk.Fund. Math. 157 (1998), 221–234

  21. [21]

    H. Hu, X. Li and Y. Yu. A note on ( − β)-shifts with the specification property. Publ. Math. Debr. 91 (2017), 123–131

  22. [22]

    Hunt and E

    B. Hunt and E. Ott. Optimal periodic orbits of chaotic systems. Phys. Rev. Lett. 76 2254

  23. [23]

    Hunt and E

    B. Hunt and E. Ott. Optimal periodic orbits of chaotic systems o ccur at low period. Phys. Rev. E 54 328

  24. [24]

    R. B. Israel. Convexity in the theory of lattice gases (Princeton Series i n Physics) Princeton, NJ: Princeton University Press (1979)

  25. [25]

    Jenkinson

    O. Jenkinson. Ergodic optimization. Discrete Continuous Dyn. Syst. A 15 (2006), 197–224

  26. [26]

    Jenkinson

    O. Jenkinson. Ergodic optimization in dynamical systems. Ergod. Th. & Dynam. Sys. 39 (2019), 2593–2618

  27. [27]

    W. Krieger. On the uniqueness of the equilibrium state. Math. Syst. Theory 8 (1974/75), 97–104

  28. [28]

    Kucherenko, M

    T. Kucherenko, M. Schmoll and C. Wolf. Ergodic theory on code d shift spaces. arXiv:2310.18855

  29. [29]

    Kwietniak, M

    D. Kwietniak, M. /suppress L¸ acka and P. Oprocha. A panorama of specification-like properties and their consequences. Dynamics and numbers , 155–186, Contemp. Math. 669 (2016), Amer. Math. Soc., Providence, RI

  30. [30]

    Lind and B

    D. Lind and B. Marcus. An introduction to symbolic dynamics and coding . Second edition. Cambridge Mathematical Library. Cambridge University Press, Cam bridge, 2021

  31. [31]

    I. D. Morris. The Ma˜ n´ e-Conze-Guivarc’h lemma for intermittent maps of the circle. Ergod. Th. & Dynam. Sys. 29 (2009), 1603–1611. ERGODIC OPTIMIZATION FOR CONTINUOUS FUNCTIONS 27

  32. [32]

    I. D. Morris. Ergodic optimization for generic continuous funct ions. Discrete Contin. Dyn. Syst. 27 (2010), 383-388

  33. [33]

    Oguchi and M

    M. Oguchi and M. Shinoda. Hausdorff dimension of the paramete rs for (α, β)-transformations with the specification property. arXiv:2403.14230

  34. [34]

    Schmeling

    J. Schmeling. Symbolic dynamics for β-shifts and self-normal numbers. Ergod. Th. & Dynam. Sys. 17 (1997), 675–694

  35. [35]

    M. Shinoda. Uncountably many maximizing measures for a dense s et of continuous functions. Nonlinearity 31 (2018), 2192–2200

  36. [36]

    Shinoda and H

    M. Shinoda and H. Takahasi. Lyapunov optimization for non-gen eric one-dimensional ex- panding Markov maps. Ergod. Th. & Dynam. Sys. 40 (2020), 2571–2592

  37. [37]

    Shinoda and K

    M. Shinoda and K. Yamamoto. Density of periodic measures and la rge deviation principle for generalised mod one transformations. Nonlinearity 37 (2023), 025003

  38. [38]

    K. Sigmund. Generic properties of invariant measures for Axiom A diffeomorphisms. Invent. math. 11 (1970), 99–109

  39. [39]

    K. Sigmund. On the distribution of periodic points for β-shifts. Monatsh. Math. 82 (1976), 247–252

  40. [40]

    K. Sigmund. On the connectedness of ergodic systems. Manuscripta Math . 22 (1977), 27–32

  41. [41]

    P. Walters. An Introduction to Ergodic Theory (Graduate Texts in Mathem atics, 79) . Springer, New York, 1982

  42. [42]

    Yamamoto

    K. Yamamoto. On the density of periodic measures for piecewise monotonic maps and their coding spaces. Tsukuba J. Math. 44 (2020), 309–324

  43. [43]

    Yuan and B

    G. Yuan and B. Hunt. Optimal orbits of hyperbolic systems. Nonlinearity 12 (1999), 1207– 1224. Department of Mathematics, Ochanomizu University, 2-1-1 O tsuka, Bunkyo-ku, Tokyo, 112-8610, JAPAN Email address : shinoda.mao@ocha.ac.jp Department of Mathematics, Keio University, Yokohama, 223 -8522, JAPAN Email address : hiroki@math.keio.ac.jp Department of ...