Mathematical analysis demonstrates sharp Dirichlet heat kernel bounds on thin annular domains, highlighting uniform geometric diffusion behavior.
Motivated by Euclidean boxes, we consider “thin” annular domains of the form U = ( a , b ) × U 0 ⊆ R n U=(a,b)×U₀⊆ Rⁿ in polar coordinates, where the spherical base U 0 ⊆ S n − 1 U₀⊆ Sⁿ⁻¹ is an inner uniform domain. We show that, with respect to the measure φ U 2 φ U² determined by the principal Dirichlet Laplacian eigenfunction φ U , such annular domains satisfy volume doubling and Poincaré inequalities uniformly over all locations and scales. This implies sharp Dirichlet heat kernel estimates expressed in terms of φ U . Our results hold uniformly over the collection of all annuli in R n Rⁿ . We also give matching two-sided bounds for the first Dirichlet Laplacian eigenfunction and eigenvalue for some annular domains including annuli in R n Rⁿ . Moreover, we prove eigenfunction inequalities for φ U under domain perturbations of U . The proofs of our main results utilize eigenfunction comparison techniques due to Lierl and the authors (“The Dirichlet heat kernel in inner uniform domains: Local results, compact domains and non-symmetric forms,” J. Funct. Anal. , vol. 266, no. 7, pp. 4189–4235, 2014; “Perturbing the principal Dirichlet eigenfunction,” arXiv preprint arXiv:2504.18783, 2025), small scale φ U 2 φ U² -Poincaré inequalities (Lierl and Saloff-Coste, “The Dirichlet heat kernel in inner uniform domains: Local results, compact domains and non-symmetric forms,” J. Funct. Anal. , vol. 266, no. 7, pp. 4189–4235, 2014), as well as a discretization technique of Coulhon and Saloff-Coste (“Variétés riemanniennes isométriques à l’infini,” Rev. Mat. Iberoam. , vol. 11, pp. 687–726, 1995). Finally, our methods also imply uniform Neumann heat kernel estimates for thin annular domains.
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Chao et al. (2026) studied this question.
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