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Unicité du problème de Cauchy pour des opérateurs du second ordre à symboles réels

Serge Alinhac (1984)

Annales de l'institut Fourier

L’auteur prouve deux théorèmes d’unicité locale du problème de Cauchy pour des opérateurs linéaires de symboles principaux p réels. Il se place dans le cas où p possède des points critiques réels ( p = d p = 0 ), au voisinage desquels il suppose une condition faible de “pseudo-convexité” (au sens d’Hörmander). Il donne alors des conditions sur le symbole sous-principal de l’opérateur qui assurent l’unicité.

Un'osservazione sulla risolubilità formale delle equazioni alle derivate parziali lineari a coefficienti costanti

Giuliano Bratti (1994)

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti Lincei. Matematica e Applicazioni

L'autore dà una condizione necessaria e sufficiente per la risolubilità formale degli operatori differenziali a coefficienti costanti, lineari, p D , in termini di prolungamento, come distribuzioni, delle u D R n - 0 , tali che p - D u = 0 .

Weakly semibounded boundary problems and sesquilinear forms

Gerd Grubb (1973)

Annales de l'institut Fourier

Let A be a 2 m order differential operator in a hermitian vector bundle E over a compact riemannian manifold Ω with boundary Γ  ; and denote by A B the realization defined by a normal differential boundary condition B ρ u = 0 ( u H 2 m ( E ) , ρ u = Cauchy data). We characterize, by an explicit condition on A and B near Γ , the realizations A B for which there exists an integro-differential sesquilinear form a B ( u , ν ) on H m ( E ) such that ( A u , ν ) = a B ( u , ν ) on D ( A B ) ; moreover we show that these are exactly the realizations satisfying a weak semiboundedness estimate:...

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