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A counterexample to Schauder estimates for elliptic operators with unbounded coefficients

Enrico Priola (2001)

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

We consider a homogeneous elliptic Dirichlet problem involving an Ornstein-Uhlenbeck operator in a half space R + 2 of R 2 . We show that for a particular initial datum, which is Lipschitz continuous and bounded on R + 2 , the second derivative of the classical solution is not uniformly continuous on R + 2 . In particular this implies that the well known maximal Hölder-regularity results fail in general for Dirichlet problems in unbounded domains involving unbounded coefficients.

A decay estimate for a class of hyperbolic pseudo-differential equations

Sandra Lucente, Guido Ziliotti (1999)

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

We consider the equation u t i Λ u = 0 , where Λ = λ D x is a first order pseudo-differential operator with real symbol λ ξ . Under a suitable convexity assumption on λ we find the decay properties for u t , x . These can be applied to the linear Maxwell system in anisotropic media and to the nonlinear Cauchy Problem u t i Λ u = f u , u 0 , x = g x . If f u is a smooth function which satisfies f u u p near u = 0 , and g is small in suitably Sobolev norm, we prove global existence theorems provided p is greater than a critical exponent.

A diffused interface whose chemical potential lies in a Sobolev space

Yoshihiro Tonegawa (2005)

Annali della Scuola Normale Superiore di Pisa - Classe di Scienze

We study a singular perturbation problem arising in the scalar two-phase field model. Given a sequence of functions with a uniform bound on the surface energy, assume the Sobolev norms W 1 , p of the associated chemical potential fields are bounded uniformly, where p > n 2 and n is the dimension of the domain. We show that the limit interface as ε tends to zero is an integral varifold with a sharp integrability condition on the mean curvature.

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