Mostrando recursos 1 - 20 de 238

  1. Interior Cauchy-Schauder Estimates for the Heat Flow in Carnot-Carathéodory Spaces

    Danielli, Donatella; Garofalo, Nicola

  2. On the Lazer-McKenna Conjecture Involving Critical and Super-critical Exponents

    Dancer, E. N.; Yan, Shusen
    We prove the Lazer-McKenna conjecture for an elliptic problem of Ambrosetti-Prodi type with critical and supercritical nonlinearities by constructing solutions concentrating on higher dimensional manifolds, under some partially symmetric assumption on the domain.

  3. Results on Positive Solutions of Elliptic Equations with a Critical Hardy-Sobolev Operator

    Cao, Daomin; Li, YanYan

  4. Explicit Yamabe Flow of an Asymmetric Cigar

    Burchard, Almut; McCann, Robert J.; Smith, Aaron
    We consider the Yamabe flow of a conformally Euclidean manifold for which the conformal factor’s reciprocal is a quadratic function of the Cartesian coordinates at each instant in time. This leads to a class of explicit solutions having no continuous symmetries (no Killing fields) but which converge in time to the cigar soliton (in two-dimensions, where the Ricci and Yamabe flows coincide) or in higher dimensions to the collapsing cigar. We calculate the exponential rate of this convergence precisely, using the logarithm of the optimal bi-Lipschitz constant to metrize distance between two Riemannian manifolds.

  5. Local Properties of Solutions of Elliptic Equations Depending on Local Properties of the Data

    Boccardo, Lucio; Leonori, Tommaso

  6. Convexity Preserving for Fully Nonlinear Parabolic Integro-Differential Equations

    Bian, Baojun; Guan, Pengfei

  7. Monotone Maps of Rn are Quasiconformal

    Astala, Kari; Iwaniec, Tadeusz; Martin, Gaven J.

  8. Construction of the Parallel Transport in the Wasserstein Space

    Ambrosio, Luigi; Gigli, Nicola

  9. Navier-Stokes Approximations to 2D Vortex Sheets in Half Plane

    Niu, Dongjuan; Jiu, Quansen; Xin, Zhouping

  10. On the Degree of Ill-posedness for Linear Problems with Noncompact Operators

    Hofmann, Bernd; Kindermann, Stefan
    In inverse problems it is quite usual to encounter equations that are ill-posed and require regularization aimed at finding stable approximate solutions when the given data are noisy. In this paper, we discuss definitions and concepts for the degree of ill-posedness for linear operator equations in a Hilbert space setting. It is important to distinguish between a global version of such degree taking into account the smoothing properties of the forward operator, only, and a local version combining that with the corresponding solution smoothness. We include the rarely discussed case of non-compact forward operators and explain why the usual notion of degree of ill-posedness cannot be used...

  11. On an Inverse Problem of Reconstructing an Unknown Coefficient in a Second Order Hyperbolic Equation from Partial Boundary Measurements

    Daveau, Christian; Khelifi, Abdessatar
    We consider the inverse problem of reconstructing an unknown coefficient in a second order hyperbolic equation from partial (on part of the boundary) dynamic boundary measurements. In this paper we prove that the knowledge of the partial Cauchy data for this class of hyperbolic PDE on any open subset

  12. SubspaceMethods for Solving Electromagnetic Inverse Scattering Problems

    Chen, Xudong; Zhong, Yu; Agarwal, Krishna
    This paper presents a survey of the subspace methods and their applications to electromagnetic inverse scattering problems. Subspace methods can be applied to reconstruct both small scatterers and extended scatterers, with the advantages of fast speed, good stability, and higher resolution. For inverse scattering problems involving small scatterers, the multiple signal classification method is used to determine the locations of scatterers and then the least-squares method is used to calculate the scattering strengths of scatterers. For inverse scattering problems involving extended scatterers, the subspace-based optimization method is used to reconstruct the refractive index of scatterers.

  13. Subdifferential Inverse Problems for Magnetohydrodynamics

    Chebotarev, Alexander
    The theory of solvability of an abstract evolution inequality in a Hilbert space for the operators with the quadratic nonlinearity is presented. It is then applied for the study of an inverse problem for MHD flows. For the three-dimensional flows the global in time existence of the weak solutions to the inverse problem is proved. For the two-dimensional flows existence and uniqueness of the strong solutions are proved.

  14. The Determination of Anisotropic Surface Impedance in Electromagnetic Scattering

    Cakoni, Fioralba; Monk, Peter
    We consider the inverse scattering problem of determining the anisotropic surface impedance of a bounded obstacle from far field measurements of the electromagnetic scattered field due to incident plane waves. Such an anisotropic boundary condition can arise from surfaces covered with patterns of conducting and insulating patches. We show that the anisotropic impedance is uniquely determined if sufficient data is available, and characterize the non-uniqueness present if a single incoming wave is used. We derive an integral equation for the surface impedance in terms of solutions of a certain interior impedance boundary value problem. These solutions can be reconstructed from far field data using the Herglotz theory...

  15. Simultaneous Reconstruction of Shape and Impedance in Corrosion Detection

    Cakoni, Fioralba; Kress, Rainer; Schuft, Christian

  16. Inverse Problems for Nonlinear Delay Systems

    Banks, H. T.; Rehm, Keri; Sutton, Karyn
    We consider inverse or parameter estimation problems for general nonlinear nonautonomous dynamical systems with delays. The parameters may be from a Euclidean set as usual, may be time dependent coefficients or may be probability distributions across a population as arise in aggregate data problems. Theoretical convergence results for finite dimensional approximations to the systems are given. Several examples are used to illustrate the ideas and computational results that demonstrate efficacy of the approximations are presented.

  17. Strong Stability with Respect to Weak Limits for a Hyperbolic System arising from Gas Chromatography

    Bourdarias, C.; Gisclon, M.; Junca, S.

  18. Vanishing Viscosity Limit for Incompressible Fluids with a Slip Boundary Condition

    Xie, Xiaoqiang; Li, Changmin

  19. Asymptotic Stability of Viscous Shock Wave for a Onedimensional Isentropic Model of Viscous Gas with Density Dependent Viscosity

    Matsumura, Akitaka; Wang, Yang
    In this paper we investigate the asymptotic stability of viscous shock wave for a onedimensional isentropic model of viscous gas with density dependent viscosity by a weighted energy method developed in the papers of Matsumura-Mei (1997) and Hashimoto-Matsumura (2007). Under the condition that the viscosity coefficient is given as a function of the absolute temperature which is determined by the Chapman-Enskog expansion theory in rarefied gas dynamics, any viscous shock wave is shown to be asymptotically stable for small initial perturbations with integral zero. This generalizes the previous result of Matsumua-Nishihara (1985) where the viscosity coefficient is given by a constant and a restriction on the strength...

  20. The Pressure Gradient System

    Zheng , Yuxi; Robinson, Zachary
    The pressure gradient system is a sub-system of the compressible Euler system. It can be obtained either through a flux splitting or an asymptotic expansion. In both derivations, the velocity field is treated as a small remnant of the original velocity of the Euler system. As such, the boundary conditions for the velocity do not necessarily follow the original ones and careful consideration is needed for the validity, integrity, and completeness of the model. We provide numerical simulations as well as basic characteristic analysis and physical considerations for the Riemann problems of the model to find out appropriate internal conditions at the origin. The study reveals...

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