Sur les equations de Monge-Ampere. I.
This paper is the second part of a work devoted to the study of variational problems (with constraints) in functional spaces defined on domains presenting some (local) form of invariance by a non-compact group of transformations like the dilations in R. This contains for example the class of problems associated with the determination of extremal functions in inequalities like Sobolev inequalities, convolution or trace inequalities... We show how the concentration-compactness principle and method...
After the study made in the locally compact case for variational problems with some translation invariance, we investigate here the variational problems (with constraints) for example in R where the invariance of R by the group of dilatations creates some possible loss of compactness. This is for example the case for all the problems associated with the determination of extremal functions in functional inequalities (like for example the Sobolev inequalities). We show here how the concentration-compactness...
Si dà una maggiorazione a priori in per le soluzioni di equazioni lineari ellittiche del secondo ordine in domini non limitati.
Si dimostra resistenza e l'unicità della soluzione del problema , nel caso in cui è un aperto di non limitato, è un operatore variazionale ellittico del secondo ordine a coefficienti misurabili e limitati e appartiene a .
Si dà una maggiorazione a priori in per le soluzioni di equazioni lineari ellittiche del secondo ordine in domini non limitati.
Si dimostra resistenza e l'unicità della soluzione del problema , nel caso in cui è un aperto di non limitato, è un operatore variazionale ellittico del secondo ordine a coefficienti misurabili e limitati e appartiene a .
We study the properties of the Wigner transform for arbitrary functions in L or for hermitian kernels like the so-called density matrices. And we introduce some limits of these transforms for sequences of functions in L, limits that correspond to the semi-classical limit in Quantum Mechanics. The measures we obtain in this way, that we call Wigner measures, have various mathematical properties that we establish. In particular, we prove they satisfy, in linear situations (Schrödinger equations) or...
We investigate, in the diffusive scaling, the limit to the macroscopic description of finite-velocity Boltzmann kinetic models, where the rate coefficient in front of the collision operator is assumed to be dependent of the mass density. It is shown that in the limit the flux vanishes, while the evolution of the mass density is governed by a nonlinear parabolic equation of porous medium type. In the last part of the paper we show that our method adapts to prove the so-called Rosseland approximation...
We prove the existence of classical solutions to certain fully non-linear second order elliptic equations with large zeroth order coefficient. The principal tool is an estimate asserting that the -norm of the solution cannot lie in a certain interval of the positive real axis.
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