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2509.05272

Simultaneously bounded and dense orbits for commuting Cartan actions

Dmitry Kleinbock, Chengyang Wu

correcthigh confidence
Category
math.DS
Journal tier
Strong Field
Processed
Sep 28, 2025, 12:57 AM

Audit review

The paper proves that for X3 = SL3(R)/SL3(Z), if F1 is a regular diagonal flow and F2,j are distinct commuting diagonal flows, then B(F1) ∩ ⋂j D(F2,j+) has full Hausdorff dimension (Theorem 1.2), via entropy-in-the-cusp control, Ledrappier–Young theory, and Marstrand slicing; it explicitly notes it cannot (at present) prove thickness/HAW for this intersection. By contrast, the model’s solution asserts a stronger HAW conclusion for S(F1,F2)=B(F1)∩D(F2+) and for the countable intersection, which is neither stated nor supported by the paper; indeed the authors remark they cannot prove thickness, contradicting the model’s HAW claim. See the statement of Theorem 1.2 and the remark (paper’s Introduction) and the closing step of the proof using slicing for the countable family of flows, as well as the use of high-entropy and non-escape-of-mass arguments (entropy in the cusp) to build the measure-theoretic backbone of the proof.

Referee report (LaTeX)

\textbf{Recommendation:} minor revisions

\textbf{Journal Tier:} strong field

\textbf{Justification:}

The manuscript delivers a first mixed-type full-dimension result on the non-compact homogeneous space X3, combining high-entropy constructions, control of entropy in the cusp to avoid escape of mass, and Marstrand slicing. The result is significant for dynamics on homogeneous spaces and has applications to uniform multiplicative Diophantine approximation. The argument is technically sound and well-motivated. Minor clarifications would further enhance readability and highlight the role of regularity and of previously known results on the dimension of bounded-orbit sets.