2410.19404
Tangents and slices of self-affine carpets
Antti Käenmäki, Alex Rutar
correctmedium confidence
- Category
- math.DS
- Journal tier
- Strong Field
- Processed
- Sep 28, 2025, 12:56 AM
- arXiv Links
- Abstract ↗PDF ↗
Audit review
The paper proves precise tangent and pointwise Assouad-dimension formulas for Gatzouras–Lalley carpets and the full-dimension level-set result, via approximate squares, symbolic slices K_η(γ), and a product-containment argument for tangents (Proposition 3.6), culminating in Theorem 3.12 and Theorem 3.14; see also Theorem A in the introduction. The candidate solution reproduces the main statements but its key upper bound for tangent dimensions relies on an invalid inequality that attempts to bound sup_u dim_H(G∩η^{-1}{u}) by the dimension of the slice at η(x). This logical misstep is critical because it is used to assert equality in the maximal tangent dimension at x. The paper’s correct route avoids this by proving h(F) ⊂ η(K)×E for any tangent F (with E a weak tangent of the vertical slice), which yields the needed upper bound. Thus, while the candidate’s conclusions align with the paper, its proof contains a fundamental gap.
Referee report (LaTeX)
\textbf{Recommendation:} no revision \textbf{Journal Tier:} strong field \textbf{Justification:} The manuscript provides sharp and conceptually illuminating results on tangent structure and pointwise Assouad dimensions for Gatzouras–Lalley carpets, with a clear path from approximate squares to symbolic slices and non-autonomous IFS regularity. The core technical inputs are well-integrated, and the level-set and a.e. attainment results are compelling and optimal within this classical class. The exposition is careful and self-contained, making the arguments accessible to specialists in fractal geometry and dimension theory.