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Xinrui Zhao

Publications and source records attributed to Xinrui Zhao.

10 recordsLinked to original sources
arXiv2026

Closed mean curvature flows with prescribed tangent flows

Given an embedded shrinker $Σ$ in $\mathbb{R}^{n+1}$ that is either closed, asymptotically conical, or a Cartesian product of such a shrinker with $\mathbb{R}^k$, we construct a closed embedded mean curvature flow whose tangent flow at the first singularity is modeled on $Σ$. We also prescribe the first-order asymptotics of the tangent flow. This result is a consequence of a more general theorem that allows us to construct mean curvature flows with an additional force whose tangent flow and first-order asymptotics at the first singularity are prescribed.

math.DG↗
arXiv2025

On the rate of convergence of cylindrical singularity in mean curvature flow

We prove that if a rescaled mean curvature flow is a global graph over the round cylinder with small gradient and converges super-exponentially fast, then it must coincide with the cylinder itself. We also show that the result is sharp with counter-examples of local graphs at arbitrarily super-exponential convergence rate with the domain expanding arbitrarily fast. The first part provides the first unique continuation result in the cylindrical setting, the generic singularity model in mean curvature flow. In sharp contrast, in the second part we construct infinite-dimensional families of Tikhonov-type examples for nonlinear equations, including the rescaled mean curvature flow, showing that unique continuation fails for local graphical solutions. These examples demonstrate the essential role of global graphical assumptions in rigidity and highlight new phenomena absent in the compact case. We also construct non-product mean curvature flows that develop singular sets as prescribed lower dimensional Euclidean space at arbitrary super-exponential rates. Our construction works in great generality for a large class of non-linear equations.

math.DG↗
arXiv2025

Enhanced Robotic Navigation in Deformable Environments using Learning from Demonstration and Dynamic Modulation

This paper presents a novel approach for robot navigation in environments containing deformable obstacles. By integrating Learning from Demonstration (LfD) with Dynamical Systems (DS), we enable adaptive and efficient navigation in complex environments where obstacles consist of both soft and hard regions. We introduce a dynamic modulation matrix within the DS framework, allowing the system to distinguish between traversable soft regions and impassable hard areas in real-time, ensuring safe and flexible trajectory planning. We validate our method through extensive simulations and robot experiments, demonstrating its ability to navigate deformable environments. Additionally, the approach provides control over both trajectory and velocity when interacting with deformable objects, including at intersections, while maintaining adherence to the original DS trajectory and dynamically adapting to obstacles for smooth and reliable navigation.

cs.RO↗
arXiv2024

Closed mean curvature flows with asymptotically conical singularities

In this paper, we prove that for any asymptotically conical self-shrinker, there exists an embedded closed hypersurface such that the mean curvature flow starting from it develops a singularity modeled on the given shrinker. The main technique is the Ważewski box argument, used by Stolarski in the proof of the corresponding theorem in the Ricci flow case. As a corollary, our construction, combined with the works of Angenent--Ilmanen--Velázquez and Chodosh--Daniels-Holgate--Schulze, implies the existence of fattening level set flows starting from smooth embedded closed hypersurfaces. These provide examples related to a question asked by Evans--Spruck.

math.DG↗
arXiv2023

Margulis Lemma on $\text{RCD}(K,N)$ spaces

We extend the Margulis Lemma for manifolds with lower Ricci curvature bounds to the $\text{RCD}(K,N)$ setting. As one of our main tools, we obtain improved regularity estimates for Regular Langrangian flows on these spaces.

math.DG↗
arXiv2022

Unique Continuation Problem on RCD Spaces. I

In this note we establish the weak unique continuation theorem for caloric functions on compact $RCD(K,2)$ spaces and show that there exists an $RCD(K,4)$ space on which there exist non-trivial eigenfunctions of the Laplacian and non-stationary solutions of the heat equation which vanish up to infinite order at one point. We also establish frequency estimates for eigenfunctions and caloric functions on the metric horn. In particular, this gives a strong unique continuation type result on the metric horn for harmonic functions with a high rate of decay at the horn tip, where it is known that the standard strong unique continuation property fails.

math.DG↗
arXiv2022

Failure of strong unique continuation for harmonic functions on RCD Spaces

Unique continuation of harmonic functions on $RCD$ space is a long-standing open problem, with little known even in the setting of Alexandrov spaces. In this paper, we establish the weak unique continuation theorem for harmonic functions on $RCD(K,2)$ spaces and give a counterexample for strong unique continuation in the setting of $ RCD(K,N)$ space for any $N\geq 4$ and any $K\in \mathbb{R}$.

math.DG↗
arXiv2021

Canonical diffeomorphisms of manifolds near spheres

For a given Riemannian manifold $(M^n, g)$ which is near standard sphere $(S^n, g_{round})$ in the Gromov-Hausdorff topology and satisfies $Rc \geq n-1$, it is known by Cheeger-Colding theory that $M$ is diffeomorphic to $S^n$. A diffeomorphism $φ: M \to S^n$ was constructed by Cheeger and Colding using Reifenberg method. In this note, we show that a desired diffeomorphism can be constructed canonically. Let $\{f_i\}_{i=1}^{n+1}$ be the first $(n+1)$-eigenfunctions of $(M, g)$ and $f=(f_1, f_2, \cdots, f_{n+1})$. Then the map $\tilde{f}=\frac{f}{|f|}: M \to S^n$ provides a diffeomorphism, and $\tilde{f}$ satisfies a uniform bi-Hölder estimate. We further show that this bi-Hölder estimate is sharp and cannot be improved to a bi-Lipschitz estimate. Our study could be considered as a continuation of the previous works of Colding and Petersen.

math.DG↗
arXiv2018

Electronic properties of a $π$-conjugated Cairo pentagonal lattice: Direct band gap, ultrahigh carrier mobility and slant Dirac cones

Two-dimensional (2D) lattices composed exclusively of pentagons represent an exceptional structure of materials correlated to the famous pentagonal tiling problem in mathematics, but their $π$-conjugation and the related electronic properties have never been reported. Here, we propose a tight-binding (TB) model for a 2D Cairo pentagonal lattice and demonstrate that $p$-$d$ $π$-conjugation in the unique framework leads to intriguing properties, such as an intrinsic direct band gap, ultra-high carrier mobility and even slant Dirac cones. On the basis of first-principles calculations, we predict a candidate material, 2D penta-NiP$_2$ monolayer, derivated from bulk NiP$_2$ crystal, to realize the predictions of the TB model. It has ultra-high carrier mobility ($\sim$$10^5-10^6$ $cm^2V^{-1}s^{-1}$) comparable to that of graphene and an intrinsic direct band gap of 0.818 eV, which are long desired for high-speed electronic devices. The stability and possible synthetic routes of penta-NiP$_2$ monolayer are also discussed.

cond-mat.mtrl-sci↗