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Subharmonic functions in sub-Riemannian settings

Andrea Bonfiglioli, Ermanno Lanconelli (2013)

Journal of the European Mathematical Society

In this paper we furnish mean value characterizations for subharmonic functions related to linear second order partial differential operators with nonnegative characteristic form, possessing a well-behaved fundamental solution Γ . These characterizations are based on suitable average operators on the level sets of Γ . Asymptotic characterizations are also considered, extending classical results of Blaschke, Privaloff, Radó, Beckenbach, Reade and Saks. We analyze as well the notion of subharmonic function...

Subharmonicity in von Neumann algebras

Thomas Ransford, Michel Valley (2005)

Studia Mathematica

Let ℳ be a von Neumann algebra with unit 1 . Let τ be a faithful, normal, semifinite trace on ℳ. Given x ∈ ℳ, denote by μ t ( x ) t 0 the generalized s-numbers of x, defined by μ t ( x ) = inf||xe||: e is a projection in ℳ i with τ ( 1 - e ) ≤ t (t ≥ 0). We prove that, if D is a complex domain and f:D → ℳ is a holomorphic function, then, for each t ≥ 0, λ 0 t l o g μ s ( f ( λ ) ) d s is a subharmonic function on D. This generalizes earlier subharmonicity results of White and Aupetit on the singular values of matrices.

Sul problema pluriarmonico in un campo sferico di 𝐂 n per n 3

Maria Adelaide Sneider (1983)

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

Let Σ be the boundary of the unit ball Ω of 𝐂 n . A set of second order linear partial differential operators, tangential to Σ , is explicitly given in such a way that, for n 3 , the corresponding PDE caractherize the trace of the solution of the pluriharmonic problem (either “in the large” or “local”), relative to Ω .

Superharmonic extension and harmonic approximation

Stephen J. Gardiner (1994)

Annales de l'institut Fourier

Let Ω be an open set in n and E be a subset of Ω . We characterize those pairs ( Ω , E ) which permit the extension of superharmonic functions from E to Ω , or the approximation of functions on E by harmonic functions on Ω .

Superharmonicity of nonlinear ground states.

Peter Lindqvist, Juan Manfredi, Eero Saksman (2000)

Revista Matemática Iberoamericana

The objective of our note is to prove that, at least for a convex domain, the ground state of the p-Laplacian operatorΔpu = div (|∇u|p-2 ∇u)is a superharmonic function, provided that 2 ≤ p ≤ ∞. The ground state of Δp is the positive solution with boundary values zero of the equationdiv(|∇u|p-2 ∇u) + λ |u|p-2 u = 0in the bounded domain Ω in the n-dimensional Euclidean space.

Sur la fonction de Green pour un domaine fin

Bent Fuglede (1975)

Annales de l'institut Fourier

Dans le cadre axiomatique de M. Brelot et R.-M. Hervé (cas A 2 y compris l’axiome de domination) on montre que, pour tout domaine U par rapport à la topologie fine et pour tout point y U , la fonction (“fine ”) de Green pour U à pôle y est caractérisée (à un facteur constant près) comme un potentiel fin > 0 relatif à U qui est finement harmonique dans U { y } .

Currently displaying 1341 – 1360 of 1784