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Estimates for k -Hessian operator and some applications

Dongrui Wan (2013)

Czechoslovak Mathematical Journal

The k -convex functions are the viscosity subsolutions to the fully nonlinear elliptic equations F k [ u ] = 0 , where F k [ u ] is the elementary symmetric function of order k , 1 k n , of the eigenvalues of the Hessian matrix D 2 u . For example, F 1 [ u ] is the Laplacian Δ u and F n [ u ] is the real Monge-Ampère operator det D 2 u , while 1 -convex functions and n -convex functions are subharmonic and convex in the classical sense, respectively. In this paper, we establish an approximation theorem for negative k -convex functions, and give several...

Estimation of vibration frequencies of linear elastic membranes

Luca Sabatini (2018)

Applications of Mathematics

The free motion of a thin elastic linear membrane is described, in a simplyfied model, by a second order linear homogeneous hyperbolic system of partial differential equations whose spatial part is the Laplace Beltrami operator acting on a Riemannian 2-dimensional manifold with boundary. We adapt the estimates of the spectrum of the Laplacian obtained in the last years by several authors for compact closed Riemannian manifolds. To make so, we use the standard technique of the doubled manifold to...

Étude de la classification topologique des fonctions unimodales

Michel Cosnard (1985)

Annales de l'institut Fourier

À l’aide de la théorie des itinéraires et des suites de tricotage, nous étudions la conjugaison topologique des fonctions unimodales. Nous introduisons la notion de conjugaison macroscopique, caractérisée par l’égalité des suites de tricotage. Puis nous présentons un théorème de classification des fonctions unimodales. Pour illustrer ces résultats, nous montrons que l’ensemble des solutions de l’équation de Feigenbaum contient une infinité de classes topologiques.

Exemples d'applications holomorphes d'indice un

Rabah Souam (1993)

Annales de l'institut Fourier

Nous construisons une famille de surfaces de Riemann hyperelliptiques, de genre variable, munies de fonctions méromorphes de degré deux et d’indice un, ce qui apporte une réponse positive à une conjecture de S. Montiel et A. Ros.

Existence and density results for retarded subdifferential evolution inclusions

Tiziana Cardinali, Simona Pieri (1996)

Discussiones Mathematicae, Differential Inclusions, Control and Optimization

In this paper we study Cauchy problems for retarded evolution inclusions, where the Fréchet subdifferential of a function F:Ω→R∪{+∞} (Ω is an open subset of a real separable Hilbert space) having a φ-monotone subdifferential of oder two is present. First we establish the existence of extremal trajectories and we show that the set of these trajectories is dense in the solution set of the original convex problem for the norm topology of the Banach space C([-r, T₀], Ω) ("strong relaxation theorem")....

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