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Hua Qiu

Publications and source records attributed to Hua Qiu.

At least 19 recordsLinked to original sources
arXiv2026

Homogenization of anisotropic diffusion on pre-Sierpi\'{n}ski carpets

We investigate the restoration of isotropy for anisotropic diffusions on pre-Sierpi\'nski carpets in the plane, a problem previously studied by Barlow, Hattori, Hattori and Watanabe \cite{BHHW} in which they obtained a weak homogenization property for the ratio of effective resistances of the anisotropic diffusions. We establish the weak convergence of these anisotropic diffusions to Brownian motion on the Sierpi\'nski carpet. As a consequence, we give an affirmative answer to the strong homogenization conjecture raised in \cite[p.3]{BHHW}.

math.PR↗
arXiv2026

Conformal Dimension of Measures and Quasisymmetric Dimension Reduction

We prove that the conformal dimension of every locally finite Borel measure is either zero or infinite. The main ingredient is a quasisymmetric dimension-reduction theorem: every full-support probability measure of finite Hausdorff dimension on a separable metric space admits quasisymmetrically equivalent metrics in which its Hausdorff dimension is arbitrarily small. In particular, every locally finite Borel measure on a doubling metric space has conformal dimension zero. We also prove that for every $n\geq 1$ and $p>0$ there are a metric space $X$, a quasisymmetric homeomorphism $f:[0,1]^n\to X$, and a Borel set $E\subset[0,1]^n$ such that $\dim_H f(E)\leq p$ and $\dim_H([0,1]^n\setminus E)\leq n-1+p$. The second bound is sharp up to $p$: if $\dim_H f(E)<1$, then $\dim_H([0,1]^n\setminus E)\geq n-1$.

math.CA↗
arXiv2026

Connective Constants on Nested Fractal Graphs

We study self-avoiding walks on the canonical one-sided graphs of Lindstrom nested fractals. We prove that the connective constant $\mu$ exists and identify $\log\mu$ with the critical inverse temperature of a finite-dimensional boundary-state renormalization. If the boundary-state partition vectors are bounded at criticality, then the fixed-length counts $c_n$ satisfy two-sided polynomial bounds around $\mu^n$. We also prove that $h$-flexibility implies $c_{n+h}/c_n\to\mu^h$. For regular polygonal $N$-gaskets, we derive exact crossing recursions, determine the smallest flexibility step $h$, and obtain explicit algebraic connective constants for the $6$- and $9$-gaskets. The Vicsek graph has no flexibility step, and its successive ratios do not converge.

math.PR↗
arXiv2025

The growth of eigenfunction extrema on p.c.f. fractals

This paper studies the growth of local extrema of Laplacian eigenfunctions on post-critically finite (p.c.f.) fractals. We establish the sharp two-sided estimate $\#\mathrm{Extr}(u_\lambda)\asymp\lambda^{d_S/2}$ for the Sierpinski gasket, demonstrating that the complexity of eigenfunctions is governed by the spectral dimension $d_S$. This behavior stands in sharp contrast to the corresponding growth law on Euclidean $n$-dimensional rectangles or balls. The attainment of the exponent $d_S/2$ reflects the high symmetry of the underlying fractal. Our result reveals a distinct spectral-geometric phenomenon on singular spaces.

math.FA↗
arXiv2025

BGD domains in p.c.f. self-similar sets II: spectral asymptotics for Laplacians

Let $K$ be a p.c.f. self-similar set equipped with a strongly recurrent Dirichlet form. Under a homogeneity assumption, for an open set $\Omega\subset K$ whose boundary $\partial \Omega$ is a graph-directed self-similar set, we prove that the eigenvalue counting function $\rho^\Omega(x)$ of the Laplacian with Dirichlet or Neumann boundary conditions (Neumann only for connected $\Omega$) has an explicit second term as $x\to +\infty$, beyond the dominant Weyl term. If $\partial\Omega$ has a strong iterated structure, we establish that \begin{equation*} \rho^\Omega(x)=\nu(\Omega)G\Big(\frac{\log x}2\Big)x^{\frac{d_S}2}+\kappa(\partial\Omega)G_1\Big(\frac{\log x}2\Big)x^{\frac d2}+o\big(x^{\frac d2}\big), \end{equation*} where $G$ and $G_1$ are bounded periodic functions, $\nu$ and $\kappa$ are certain reference measures, and $d_S$ and $d$ are dimension-related parameters.

math.FA↗
arXiv2025

Subwavelength plasmonic antennas based on asymmetric split-ring-resonators for high near-field enhancements

As for plasmonic antenna structures that generate localized near-field enhancement, the most effective current implementations are based on electric dipole resonance modes, but this approach also imposes limitations on their further optimization. Here we introduce an ASRR structure whose ASR mode enables differential charge distribution across both sides of the split. Through asymmetric regulation, charges at one end can become highly localized, thereby achieving efficient near-field enhancement. The formation of this structure was initially driven by a hybrid computational framework integrating evolutionary optimization with residual neural networks, and subsequently simplified into an ASRR prototype using the Occam's Razor principle. The ASRR dimer structure can achieve an electric field intensity enhancement over 6.5 times larger than a traditional nanorod dimer, while maintaining a compact size (<1/3 the working wavelength). The ASRR configuration also demonstrates superior Purcell factor and fluorescence enhancement. These results can find applications in surface-enhanced spectroscopy, nonlinear optics, and quantum light-matter interactions.

physics.optics↗
arXiv2024

The Hausdorff measure and uniform fibre conditions for Bara\'nski carpet

For a self-affine carpet $K$ of Bara\'{n}ski, we establish a dichotomy: $ \text{either }\quad 0<\mathcal{H}^{\dim_{\text{H}} K}(K)<+\infty \quad\text{ or } \quad\mathcal{H}^{\dim_{\text{H}} K}(K)=+\infty. $ We introduce four types of uniform fibre condition for $K$: Hausdorff ($\textbf{u.f.H}$), Box ($\textbf{u.f.B}$), Assouad ($\textbf{u.f.A}$), and Lower ($\textbf{u.f.L}$), which are progressively stronger, with $ \textbf{u.f.L} \Longrightarrow \textbf{u.f.A} \Longrightarrow \textbf{u.f.B} \Longrightarrow \textbf{u.f.H}, $ and each implication is strict. The condition $\textbf{u.f.H}$ serves as a criterion for the dichotomy. The remaining three conditions provide an equivalent characterization for the coincidence of any two distinct dimensions. The condition $\textbf{u.f.L}$ is also equivalent to the Ahlfors regularity of $K$. As a corollary, $\dim_{\text{H}} K=\dim_{\text{B}} K$ is sufficient but not necessary for $0<\mathcal{H}^{\dim_{\text{H}} K}(K)<+\infty$.

math.CA↗
arXiv2024

Assouad and lower dimensions of graph-directed Bedford-McMullen carpets

We calculate the Assouad and lower dimensions of graph-directed Bedford-McMullen carpets, which reflect the extreme local scaling laws of the sets, in contrasting with known results on Hausdorff and box dimensions. We also investigate the relationship between distinct dimensions. In particular, we identify an equivalent condition when the box and Assouad dimension coincide, and show that under this condition, the Hausdorff dimension attains the same value.

math.CA↗
arXiv2024

BGD domains in p.c.f. self-similar sets I: boundary value problems for harmonic functions

We study the boundary value problems for harmonic functions on open connected subsets of post-critically finite (p.c.f.) self-similar sets, on which the Laplacian is defined through a strongly recurrent self-similar local regular Dirichlet form. For a p.c.f. self-similar set $K$, we prove that for any open connected subset $Ω\subset K$ whose "geometric" boundary is a graph-directed self-similar set, there exists a finite number of matrices called $\textit{flux transfer matrices}$ whose products generate the hitting probability from a point in $Ω$ to the "resistance" boundary $\partial Ω$. The harmonic functions on $Ω$ can be expressed by integrating functions on $\partial Ω$ against the probability measures. Furthermore, we obtain a two-sided estimate of the energy of a harmonic function in terms of its values on $\partial Ω$.

math.FA↗
arXiv2024

Dirichlet forms on unconstrained Sierpinski carpets

We construct symmetric self-similar Dirichlet forms on unconstrained Sierpinski carpets, which are natural extension of planar Sierpinski carpets by allowing the small cells to live off the $1/k$ grids. The intersection of two cells can be a line segment of irrational length, and the non-diagonal assumption is dropped in this recurrent setting.

math.FA↗
arXiv2024

Uniqueness and convergence of resistance forms on unconstrained Sierpinski carpets

We prove the uniqueness of self-similar $D_4$-symmetric resistance forms on unconstrained Sierpinski carpets ($\mathcal{USC}$'s). Moreover, on a sequence of $\mathcal{USC}$'s $K_n, n\geq 1$ converging in Hausdorff metric, we show that the associated diffusion processes converge in distribution if and only if the geodesic metrics on $K_n, n\geq 1$ are equicontinuous with respect to the Euclidean metric.

math.FA↗
arXiv2024

Relations between near-field enhancements and Purcell factors in hybrid nanostructures of plasmonic antennas and dielectric cavities

Strong near-field enhancements (NFEs) of nanophotonic structures are believed to be closely related to high Purcell factors (FP). Here, we theoretically show that the correlation is partially correct; the extinction cross section (σ) response is also critical in determining FP. The divergence between NFE and FP is especially pronounced in plasmonic-dielectric hybrid systems, where the plasmonic antenna supports dipolar plasmon modes and the dielectric cavity hosts Mie-like resonances. The cavity's enhanced-field environment can boost the antenna's NFEs, but the FP is not increased concurrently due to the larger effective σ that is intrinsic to the FP calculations. Interestingly, the peak FP for the coupled system can be predicted by using the NFE and σ responses. Furthermore, the limits for FP of coupled systems are considered; they are determined by the sum of the FP of a redshifted (or modified, if applicable) antenna and an individual cavity. This contrasts starkly with the behavior of NFE which is closely associated with the multiplicative effects of the NFEs provided by the antenna and the dielectric cavity. The differing behaviors of NFE and FP in hybrid cavities have varied impacts on relevant nanophotonic applications such as fluorescence, Raman scattering and enhanced light-matter interactions.

physics.optics↗
arXiv2023

$L^q$-spectra of box-like graph-directed self-affine measures: closed forms, with rotation

We consider $L^q$-spectra of planar graph-directed self-affine measures generated by diagonal or anti-diagonal matrices. Assuming the directed graph is strongly connected and the system satisfies the rectangular open set condition, we obtain a general closed form expression for the $L^q$-spectra. Consequently, we obtain a closed form expression for box dimensions of associated planar graph-directed box-like self-affine sets. We also provide a precise answer to a question of Fraser in 2016 concerning the $L^q$-spectra of planar self-affine measures generated by diagonal matrices.

math.CA↗
arXiv2023

Dirichlet forms on unconstrained Sierpinski carpets in $\mathbb{R}^3$

We prove the existence of a strongly local, regular, self-similar Dirichlet form with a sub-Gaussian heat kernel estimate on an unconstrained Sierpinski carpet in $\mathbb{R}^3$. In the setting under consideration, the walk dimension $d_W$ and the Hausdorff dimension $d_H$ always satisfy the inequality that $d_H>d_W$.

math.FA↗
arXiv2022

Hausdorff and box dimension of self-affine set in non-Archimedean field

In this paper we consider affine iterated function systems in locally compact non-Archimedean field $\mathbb{F}$. We establish the theory of singular value composition in $\mathbb{F}$ and compute box and Hausdorff dimension of self-affine set in $\mathbb{F}^n$, in generic sense, which is an analogy of Falconer's result for real case. The result has the advantage that no additional assumptions needed to be imposed on the norms of linear parts of affine transformation while such norms are strictly less than $\frac{1}{2}$ for real case, which benefits from the non-Archimedean metric on $\mathbb{F}$.

math.CA↗
arXiv2022

Self-similar Dirichlet forms on polygon carpets

We construct symmetric self-similar diffusions with sub-Gaussian heat kernel estimates on two types of polygon carpets, which are natural generalizations of planner Sierpinski carpets (SC). The first ones are called perfect polygon carpets that are natural analogs of SC in that any intersection cells are either side-to-side or point-to-point. The second ones are called bordered polygon carpets which satisfy the boundary including condition as SC but allow distinct contraction ratios.

math.DS↗