Uniformly Positive Mean Dimension
Pith reviewed 2026-07-03 18:09 UTC · model grok-4.3
The pith
A hub-and-spoke construction on symbolic systems transfers uniformly positive entropy to uniformly positive mean dimension and produces examples with completely positive mean dimension but neither uniform property.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
To a symbolic system X we associate the hub-and-spoke system Spoke(X) obtained by replacing each symbol by a one-dimensional spoke attached to a common hub. If X admits a shift-invariant measure of full support, then Spoke(X) has completely positive mean dimension. If X has uniformly positive entropy, then Spoke(X) has uniformly positive mean dimension. Using symbolic codings of irrational rotations on tori, we construct hub-and-spoke systems with completely positive mean dimension but without uniformly positive mean dimension or uniformly positive entropy. The examples are nondegenerate: the relevant covers have zero mean dimension and zero entropy, but when refined by iterating under the d
What carries the argument
The hub-and-spoke construction Spoke(X), which replaces each symbol of the symbolic system X with a one-dimensional spoke attached to a common hub.
If this is right
- A symbolic system with a full-support invariant measure yields a hub-and-spoke system with completely positive mean dimension.
- Uniformly positive entropy on the base system implies uniformly positive mean dimension on the associated spoke system.
- There exist hub-and-spoke systems with completely positive mean dimension that lack uniformly positive mean dimension and uniformly positive entropy.
- In the constructed examples, certain open covers have zero mean dimension and zero entropy while their iterated covering numbers under the dynamics are unbounded.
Where Pith is reading between the lines
- The spoke construction may allow separation of complete positivity from uniform positivity in mean dimension across a wider class of systems.
- Similar geometric attachments could relate mean dimension to other invariants in systems that are not originally symbolic.
- The phenomenon of zero single-cover contribution yet unbounded iterated numbers may appear in other dimension-like invariants under iteration.
Load-bearing premise
The spoke replacement preserves the relevant dynamical properties at the level of fixed open covers when associating the system and when proving the implications from entropy or full-support measures.
What would settle it
A symbolic system with uniformly positive entropy whose Spoke version admits an open cover whose mean dimension contribution is zero would falsify the uniform positivity transfer.
read the original abstract
We study the relation between uniformly positive entropy and uniformly positive mean dimension at the level of fixed open covers. To a symbolic system X, we associate a hub-and-spoke system Spoke(X), obtained by replacing each symbol by a one-dimensional spoke attached to a common hub. We prove that if X admits a shift-invariant measure of full support, then Spoke(X) has completely positive mean dimension. We also prove that if X has uniformly positive entropy, then Spoke(X) has uniformly positive mean dimension. Finally, using symbolic codings of irrational rotations on tori, we construct hub-and-spoke systems with completely positive mean dimension but without uniformly positive mean dimension or uniformly positive entropy. The examples are nondegenerate: the relevant covers have zero mean dimension and zero entropy, but when refined by iterating under the dynamics the corresponding covering numbers are unbounded.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper studies the relation between uniformly positive entropy and uniformly positive mean dimension at the level of fixed open covers. To a symbolic system X, it associates a hub-and-spoke system Spoke(X) obtained by replacing each symbol by a one-dimensional spoke attached to a common hub. It proves that if X admits a shift-invariant measure of full support, then Spoke(X) has completely positive mean dimension. It also proves that if X has uniformly positive entropy, then Spoke(X) has uniformly positive mean dimension. Finally, using symbolic codings of irrational rotations on tori, it constructs hub-and-spoke systems with completely positive mean dimension but without uniformly positive mean dimension or uniformly positive entropy. The examples are nondegenerate: the relevant covers have zero mean dimension and zero entropy, but when refined by iterating under the dynamics the corresponding covering numbers are unbounded.
Significance. If the results hold, the Spoke(X) construction and the separation examples provide a concrete way to distinguish completely positive mean dimension from the uniformly positive variant (and from uniformly positive entropy) while preserving nondegeneracy via unbounded iterated covering numbers. The implications from full-support measures and from uniformly positive entropy are useful for relating these invariants at the fixed-cover level.
Simulated Author's Rebuttal
We thank the referee for their accurate summary of the manuscript and for highlighting the significance of the Spoke(X) construction and the separation examples. The recommendation is listed as uncertain, but the report contains no major comments or specific criticisms. We therefore have no points to address point-by-point and propose no changes.
Circularity Check
No significant circularity detected
full rationale
The paper establishes theorems relating uniformly positive entropy to uniformly positive mean dimension via explicit constructions of Spoke(X) systems from symbolic X, along with counterexamples using irrational rotation codings. These are presented as proved implications and constructions at the level of fixed open covers, with no reduction of target quantities (mean dimension, entropy) to fitted parameters, self-definitions, or load-bearing self-citations. The derivation chain relies on direct dynamical arguments and examples rather than renaming or importing uniqueness from prior author work. The central claims remain independent of the inputs by construction.
Axiom & Free-Parameter Ledger
axioms (2)
- domain assumption Mean dimension and entropy are well-defined for the open covers of the constructed Spoke(X) system and behave functorially under the hub-and-spoke replacement.
- domain assumption Symbolic codings of irrational rotations on tori exist and can be used to produce systems whose covers have zero entropy and zero mean dimension before iteration.
invented entities (1)
-
Spoke(X) hub-and-spoke system
no independent evidence
Reference graph
Works this paper leans on
-
[1]
1997 , author =
An introduction to infinite ergodic theory , publisher =. 1997 , author =
1997
-
[2]
Set theory (
Adams, Scot , TITLE =. Set theory (. 2002 , MRCLASS =
2002
-
[3]
Symbolic dynamics and its applications (New Haven, CT, 1991) , volume=
Fully positive topological entropy and topological mixing , author=. Symbolic dynamics and its applications (New Haven, CT, 1991) , volume=
1991
-
[4]
Groups, Geometry, and Dynamics , year=
Local mean dimension theory for sofic group actions , author=. Groups, Geometry, and Dynamics , year=
-
[5]
arXiv e-prints , keywords =
Adiceam, Faustin and Nesharim, Erez and Lunnon, Fred , title =. arXiv e-prints , keywords =. 2018
2018
-
[6]
Adler, R. L. and Weiss, B. , title =. Proc. Nat. Acad. Sci. U.S.A. , year =
-
[7]
Adler, R. L. and Konheim, A. G. and McAndrew, M. H. , TITLE =. Trans. Amer. Math. Soc. , FJOURNAL =. 1965 , PAGES =. doi:10.2307/1994177 , URL =
-
[8]
Agmon, Shmuel , TITLE =. 2010 , PAGES =. doi:10.1090/chel/369 , URL =
-
[9]
Aka, Menny and Shapira, Uri , title =
-
[10]
Diophantine properties of nilpotent Lie groups
Diophantine properties of nilpotent Lie groups , author=. arXiv preprint arXiv:1307.1489 , year=
work page internal anchor Pith review Pith/arXiv arXiv
-
[11]
Aka, Menny and Einsiedler, Manfred and Shapira, Uri , TITLE =. Invent. Math. , FJOURNAL =. 2016 , NUMBER =. doi:10.1007/s00222-016-0655-7 , URL =
-
[12]
arXiv e-prints , FJOURNAL =
Aka, Menny and Einsiedler, Manfred and Shapira, Uri , TITLE =. arXiv e-prints , FJOURNAL =. 2015 , eid =
2015
-
[13]
Duke Mathematical Journal , number =
Menny Aka and Manfred Einsiedler and Andreas Wieser , title =. Duke Mathematical Journal , number =. 2022 , doi =
2022
-
[14]
2021 , eprint=
Simultaneous supersingular reductions of CM elliptic curves , author=. 2021 , eprint=
2021
-
[15]
Anantharaman, Nalini , TITLE =. Ann. of Math. (2) , FJOURNAL =. 2008 , NUMBER =. doi:10.4007/annals.2008.168.435 , URL =
-
[16]
Half-delocalization of eigenfunctions for the
Anantharaman, Nalini and Nonnenmacher, St. Half-delocalization of eigenfunctions for the. Ann. Inst. Fourier (Grenoble) , FJOURNAL =. 2007 , NUMBER =
2007
-
[17]
Nalini Anantharaman and St\'ephane Nonnenmacher , title =
-
[18]
Athreya, Jayadev S. , TITLE =. Geom. Dedicata , FJOURNAL =. 2006 , PAGES =. doi:10.1007/s10711-006-9058-z , URL =
-
[19]
Athreya, Jayadev S. and Margulis, Gregory A. , TITLE =. J. Mod. Dyn. , FJOURNAL =. 2009 , NUMBER =. doi:10.3934/jmd.2009.3.359 , URL =
-
[20]
Scenery entropy as an invariant of
Tim Austin , year=. Scenery entropy as an invariant of
-
[21]
Avila, Artur and Viana, Marcelo , TITLE =. Acta Math. , FJOURNAL =. 2007 , NUMBER =. doi:10.1007/s11511-007-0012-1 , URL =
-
[22]
Avila, Artur and Forni, Giovanni , TITLE =. Ann. of Math. (2) , FJOURNAL =. 2007 , NUMBER =. doi:10.4007/annals.2007.165.637 , URL =
-
[23]
Small eigenvalues of the Laplacian for algebraic measures in moduli space, and mixing properties of the Teichm " uller flow , author=. arXiv preprint arXiv:1011.5472 , year=
work page internal anchor Pith review Pith/arXiv arXiv
-
[24]
Avila, Artur and Gou. Exponential mixing for the. Publ. Math. Inst. Hautes \'Etudes Sci. , FJOURNAL =. 2006 , PAGES =. doi:10.1007/s10240-006-0001-5 , URL =
-
[25]
Baker, A. and W. Logarithmic forms and group varieties , journal =. 1993 , volume =
1993
-
[26]
1975 , PAGES =
Baker, Alan , TITLE =. 1975 , PAGES =
1975
-
[27]
Combinatorica , volume=
A statistical theorem of set addition , author=. Combinatorica , volume=. 1994 , publisher=
1994
-
[28]
2020 , eprint=
Slow entropy of some combinatorial constructions , author=. 2020 , eprint=
2020
-
[29]
Barak, Boaz and Impagliazzo, Russell and Wigderson, Avi , TITLE =. SIAM J. Comput. , FJOURNAL =. 2006 , NUMBER =. doi:10.1137/S0097539705447141 , URL =
-
[30]
Alex Barnett , title =
-
[31]
2000 , author =
Ergodic theory and topological dynamics of group actions on homogeneous spaces , publisher =. 2000 , author =
2000
-
[32]
2014 , Eprint =
Yves Benoist and Nicolas de Saxcé , Title =. 2014 , Eprint =
2014
-
[33]
Benoist, Yves and Oh, Hee , TITLE =. Geom. Funct. Anal. , FJOURNAL =. 2007 , NUMBER =. doi:10.1007/s00039-006-0585-4 , URL =
-
[34]
Benoist, Yves and Quint, Jean-Francois , TITLE =. Invent. Math. , FJOURNAL =. 2012 , NUMBER =. doi:10.1007/s00222-011-0328-5 , URL =
-
[35]
Mesures stationnaires et ferm\'
Benoist, Yves and Quint, Jean-Fran. Mesures stationnaires et ferm\'. Ann. of Math. (2) , FJOURNAL =. 2011 , NUMBER =. doi:10.4007/annals.2011.174.2.8 , URL =
-
[36]
Stationary measures and invariant subsets of homogeneous spaces (
Benoist, Yves and Quint, Jean-Fran. Stationary measures and invariant subsets of homogeneous spaces (. Ann. of Math. (2) , FJOURNAL =. 2013 , NUMBER =. doi:10.4007/annals.2013.178.3.5 , URL =
-
[37]
Stationary measures and invariant subsets of homogeneous spaces (
Benoist, Yves and Quint, Jean-Fran. Stationary measures and invariant subsets of homogeneous spaces (. J. Amer. Math. Soc. , FJOURNAL =. 2013 , NUMBER =. doi:10.1090/S0894-0347-2013-00760-2 , URL =
-
[38]
Bentkus, V. and G. Lattice point problems and distribution of values of quadratic forms , JOURNAL =. 1999 , NUMBER =. doi:10.2307/121060 , URL =
-
[39]
Berend, Daniel , title =. Trans. Amer. Math. Soc. , year =
-
[40]
Ergodic Theory Dynam
Berend, Daniel , title =. Ergodic Theory Dynam. Systems , year =
-
[41]
Beresnevich, V. V. and Bernik, V. I. and Kleinbock, D. Y. and Margulis, G. A. , title =. Mosc. Math. J. , year =
-
[42]
2020 , note=
Winning property of badly approximable points on curves , author=. 2020 , note=
2020
-
[43]
Victor Beresnevich and Erez Nesharim and Lei Yang , year=. Bad(. GAFA , note=
-
[44]
and Kleinbock, D
Bernik, V. and Kleinbock, D. and Margulis, G. A. , title =. Internat. Math. Res. Notices , year =
-
[45]
Bergeron, Nicolas and Seng\"un, Mehmet Haluk and Venkatesh, Akshay , TITLE =. Duke Math. J. , FJOURNAL =. 2016 , NUMBER =. doi:10.1215/00127094-3450429 , URL =
-
[46]
Bergeron, Nicolas and Venkatesh, Akshay , TITLE =. J. Inst. Math. Jussieu , FJOURNAL =. 2013 , NUMBER =. doi:10.1017/S1474748012000667 , URL =
-
[47]
1989 , PAGES =
Beurling, Arne , TITLE =. 1989 , PAGES =
1989
-
[48]
Bhargava, Manjul , TITLE =. Ann. of Math. (2) , FJOURNAL =. 2008 , NUMBER =. doi:10.4007/annals.2008.167.53 , URL =
-
[49]
Bhargava, Manjul , TITLE =. Ann. of Math. (2) , FJOURNAL =. 2004 , NUMBER =. doi:10.4007/annals.2004.159.1329 , URL =
-
[50]
Bhargava, Manjul , TITLE =. Ann. of Math. (2) , FJOURNAL =. 2004 , NUMBER =. doi:10.4007/annals.2004.159.865 , URL =
-
[51]
Bhattacharya, Siddhartha , title =
-
[52]
Israel J
Bhattacharya, Siddhartha and Schmidt, Klaus , title =. Israel J. Math. , year =
-
[53]
An introduction to quantum equidistribution , booktitle =
de Bi. An introduction to quantum equidistribution , booktitle =
-
[54]
Blomer, Valentin and Harcos, Gergely and Michel, Philippe , TITLE =. Ann. Sci. \'. 2007 , NUMBER =. doi:10.1016/j.ansens.2007.05.003 , URL =
-
[55]
Small gaps in the spectrum of the rectangular billiard , JOURNAL =
Blomer, Valentin and Bourgain, Jean and Radziwi , Maksym and Rudnick, Ze\'. Small gaps in the spectrum of the rectangular billiard , JOURNAL =. 2017 , NUMBER =. doi:10.24033/asens.2645 , URL =
-
[56]
Bombieri, Enrico and Gubler, Walter , TITLE =. 2006 , PAGES =. doi:10.1017/CBO9780511542879 , URL =
-
[57]
Boshernitzan, Michael D. , TITLE =. Proc. Amer. Math. Soc. , FJOURNAL =. 1994 , NUMBER =. doi:10.2307/2160842 , URL =
-
[58]
Borel, Armand and Harish-Chandra , title =. Ann. of Math. (2) , year =
-
[59]
Bourgain, Jean , TITLE =. J. Anal. Math. , FJOURNAL =. 2010 , PAGES =. doi:10.1007/s11854-010-0028-x , URL =
-
[60]
, title =
Bourgain, J. , title =. Geom. Funct. Anal. , year =
-
[61]
Bourgain, Jean , TITLE =. Geom. Funct. Anal. , FJOURNAL =. 2009 , NUMBER =. doi:10.1007/s00039-008-0691-6 , URL =
-
[62]
Exponential sum estimates over subgroups of
Bourgain, J , journal=. Exponential sum estimates over subgroups of. 2005 , publisher=
2005
-
[63]
Geometric and Functional Analysis , volume=
On triples in arithmetic progression , author=. Geometric and Functional Analysis , volume=. 1999 , publisher=
1999
-
[64]
Bourgain, J. , TITLE =. Geom. Funct. Anal. , FJOURNAL =. 1999 , NUMBER =. doi:10.1007/s000390050087 , URL =
-
[65]
Bourgain, J. , TITLE =. Int. J. Number Theory , FJOURNAL =. 2005 , NUMBER =. doi:10.1142/S1793042105000108 , URL =
-
[66]
Bourgain, Jean and Demeter, Ciprian , TITLE =. Ann. of Math. (2) , FJOURNAL =. 2015 , NUMBER =. doi:10.4007/annals.2015.182.1.9 , URL =
-
[67]
Bourgain, Jean and Furman, Alex and Lindenstrauss, Elon and Mozes, Shahar , title =. C. R. Math. Acad. Sci. Paris , year =
-
[68]
Bourgain, Jean and Furman, Alex and Lindenstrauss, Elon and Mozes, Shahar , TITLE =. J. Amer. Math. Soc. , FJOURNAL =. 2011 , NUMBER =. doi:10.1090/S0894-0347-2010-00674-1 , URL =
-
[69]
Bourgain, J. and Glibichuk, A. A. and Konyagin, S. V. , TITLE =. J. London Math. Soc. (2) , FJOURNAL =. 2006 , NUMBER =. doi:10.1112/S0024610706022721 , URL =
-
[70]
Bourgain, Jean and Gamburd, Alex , TITLE =. Invent. Math. , FJOURNAL =. 2008 , NUMBER =. doi:10.1007/s00222-007-0072-z , URL =
-
[71]
Bourgain, J. and Gamburd, A. , TITLE =. J. Eur. Math. Soc. (JEMS) , FJOURNAL =. 2012 , NUMBER =. doi:10.4171/JEMS/337 , URL =
-
[72]
Uniform expansion bounds for Cayley graphs of
Bourgain, Jean and Gamburd, Alex , journal=. Uniform expansion bounds for Cayley graphs of
-
[73]
Bourgain, J. and Katz, N. and Tao, T. , TITLE =. Geom. Funct. Anal. , FJOURNAL =. 2004 , NUMBER =. doi:10.1007/s00039-004-0451-1 , URL =
-
[74]
Bourgain, Jean and Konyagin, S. V. , title =. C. R. Math. Acad. Sci. Paris , year =
-
[75]
Bourgain, Jean and Lindenstrauss, Elon , title =
-
[76]
Bourgain, Jean and Lindenstrauss, Elon , title =. Comm. Math. Phys. , year =
-
[77]
Bourgain, Jean and Lindenstrauss, Elon and Michel, Philippe and Venkatesh, Akshay , TITLE =. Ergodic Theory Dynam. Systems , FJOURNAL =. 2009 , NUMBER =. doi:10.1017/S0143385708000898 , URL =
-
[78]
Bourgain, Jean and Varj\'u, P\'eter P. , TITLE =. Invent. Math. , FJOURNAL =. 2012 , NUMBER =. doi:10.1007/s00222-011-0345-4 , URL =
-
[79]
2017 , eprint=
On the affine random walk on the torus , author=. 2017 , eprint=
2017
-
[80]
Boyle, Mike and Downarowicz, Tomasz , TITLE =. Invent. Math. , FJOURNAL =. 2004 , NUMBER =. doi:10.1007/s00222-003-0335-2 , URL =
discussion (0)
Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.