1,721,014 research outputs found

    Improved bounds for Hermite-Hadamard inequalities in higher dimensions

    No full text
    Let OmegasubsetmathbbRnOmega subset mathbb{R}^n be a convex domain and let f:OmegaightarrowmathbbRf:Omega ightarrow mathbb{R} be a positive, subharmonic function (i.e. Deltafgeq0Delta f geq 0). Then rac1OmegaintOmegafdxleqraccnpartialOmegaintpartialOmegafdsigma, rac{1}{|Omega|} int_{Omega}{f dx} leq rac{c_n}{ |partial Omega| } int_{partial Omega}{ f dsigma}, where cnleq2n3/2c_n leq 2n^{3/2}. This inequality was previously only known for convex functions with a much larger constant. We also show that the optimal constant satisfies cngeqn1c_n geq n-1. As a byproduct, we establish the following sharp geometric inequality for two convex domains where one contains the other Omega2subsetOmega1subsetmathbbRn Omega_2 subset Omega_1 subset mathbb{R}^n: rac{|partial Omega_1|}{|Omega_1|} rac{| Omega_2|}{|partial Omega_2|} leq n.$

    On a time-depending Monge-Ampère type equation

    No full text
    In this paper, we prove a comparison result between a solution u(x, t), x is an element of Omega subset of R-2, t is an element of (0, T), of a time depending equation involving the Monge-Ampere operator in the plane and the solution of a conveniently symmetrized parabolic equation. To this aim, we prove a derivation formula for the integral of a smooth function g(x, t) over sublevel sets of u, {x is an element of Omega : u(x, t) < nu}, nu is an element of R, having the same perimeter in R-2. (C) 2012 Elsevier Ltd. All rights reserved

    On the symmetry of solutions to a k-Hessian type equation

    No full text
    In this note we prove that if u is a negative solution to a nonlinear elliptic equation involving a Hessian operator, and u is zero on the boundary of a ball, then u is radially symmetric and increasing along the radii

    Comparison results for Monge - Ampère type equations with lower order terms

    No full text
    In this paper we deal with Monge-Ampère type equations in two dimensions and, using the symmetrization with respect to the perimeter, we prove some comparison results for solutions of such equations involving the solutions of conveniently symmetrized problems

    I poligoni: dai mosaici dell’Alhambra alle incisioni di Escher

    No full text
    Descrizione delle attività svolte durante l'omonimo laboratorio tenuto per il PLS matematica nell'anno 201

    Existence and comparison results for a singular semilinear elliptic equation with a lower order term

    No full text
    This paper deals with the homogeneous Dirichlet problem for a singular semilinear elliptic equation with a first order term. When the datum is bounded we prove an existence result and we show that any solution can be compared with the solution to a suitable symmetrized problem

    A sharp estimate for Neumann eigenvalues of the Laplace-Beltrami operator for domains in a hemisphere

    Full text link
    Here, we prove an isoperimetric inequality for the harmonic mean of the first N - 1 non-trivial Neumann eigenvalues of the Laplace-Beltrami operator for domains contained in a hemisphere of N
    corecore