649 research outputs found

    Regularity properties of distributions through sequences of functions

    Get PDF
    We give necessary and sufficient criteria for a distribution to be smooth or uniformly H\"{o}lder continuous in terms of approximation sequences by smooth functions; in particular, in terms of those arising as regularizations (T∗ϕn)(T\ast\phi_{n}).Comment: 10 page

    Medial Features for Superpixel Segmentation

    Get PDF
    Image segmentation plays an important role in computer vision and human scene perception. Image oversegmentation is a common technique to overcome the problem of managing the high number of pixels and the reasoning among them. Specifically, a local and coherent cluster that contains a statistically homogeneous region is denoted as a superpixel. In this paper we propose a novel algorithm that segments an image into superpixels employing a new kind of shape centered feature which serve as a seed points for image segmentation, based on Gradient Vector Flow fields (GVF) [14]. The features are located at image locations with salient symmetry. We compare our algorithm to state-of-the-art superpixel algorithms and demonstrate a performance increase on the standard Berkeley Segmentation Dataset

    Polyharmonic approximation on the sphere

    Full text link
    The purpose of this article is to provide new error estimates for a popular type of SBF approximation on the sphere: approximating by linear combinations of Green's functions of polyharmonic differential operators. We show that the LpL_p approximation order for this kind of approximation is σ\sigma for functions having LpL_p smoothness σ\sigma (for σ\sigma up to the order of the underlying differential operator, just as in univariate spline theory). This is an improvement over previous error estimates, which penalized the approximation order when measuring error in LpL_p, p>2 and held only in a restrictive setting when measuring error in LpL_p, p<2.Comment: 16 pages; revised version; to appear in Constr. Appro

    Stable Determination of the Electromagnetic Coefficients by Boundary Measurements

    Full text link
    The goal of this paper is to prove a stable determination of the coefficients for the time-harmonic Maxwell equations, in a Lipschitz domain, by boundary measurements

    Stability of complex hyperbolic space under curvature-normalized Ricci flow

    Full text link
    Using the maximal regularity theory for quasilinear parabolic systems, we prove two stability results of complex hyperbolic space under the curvature-normalized Ricci flow in complex dimensions two and higher. The first result is on a closed manifold. The second result is on a complete noncompact manifold. To prove both results, we fully analyze the structure of the Lichnerowicz Laplacian on complex hyperbolic space. To prove the second result, we also define suitably weighted little H\"{o}lder spaces on a complete noncompact manifold and establish their interpolation properties.Comment: Some typos in version 2 are correcte

    On the Fourier transform of the characteristic functions of domains with C1C^1 -smooth boundary

    Full text link
    We consider domains D⊆RnD\subseteq\mathbb R^n with C1C^1 -smooth boundary and study the following question: when the Fourier transform 1D^\hat{1_D} of the characteristic function 1D1_D belongs to Lp(Rn)L^p(\mathbb R^n)?Comment: added two references; added footnotes on pages 6 and 1

    Thermodynamical Consistent Modeling and Analysis of Nematic Liquid Crystal Flows

    Full text link
    The general Ericksen-Leslie system for the flow of nematic liquid crystals is reconsidered in the non-isothermal case aiming for thermodynamically consistent models. The non-isothermal model is then investigated analytically. A fairly complete dynamic theory is developed by analyzing these systems as quasilinear parabolic evolution equations in an Lp−LqL^p-L^q-setting. First, the existence of a unique, local strong solution is proved. It is then shown that this solution extends to a global strong solution provided the initial data are close to an equilibrium or the solution is eventually bounded in the natural norm of the underlying state space. In these cases, the solution converges exponentially to an equilibrium in the natural state manifold
    • …
    corecore