On démontre plusieurs théorèmes concernant le balayage des mesures sur un espace harmonique satisfaisant aux axiomes de Bauer, parmi lesquels nous indiquons les suivants : a) la balayée ${\mu }_{A\cup B}$ d’une mesure $\mu$ sur la réunion ${\mu }^A\vee {\mu }^B$ (dans l’espace de Riesz de mesure) ; b) ${ϵ}_x^A\ne {ϵ}_x$ caractérise l’effilement de $A$ en $x$ ; c) il existe un potentiel fini et continue $p$ tel que pour tout ensemble $A\left\{x\right|{\widehat{R}}_p\left(x\right)\<p\left(x\right)\}$ est exactement l’ensemble des points où $A$ est effilé ; d) ${\mu }^A$ est portée par la fermeture fine de $A$ ; e) si $A$ et $B$ sont...

Let $\Delta u={\Sigma }_i\frac{{\partial }^2}{{\partial }_{x_i}^2}$, $Lu={\Sigma }_{i,j}{a}_{ij}\frac{{\partial }^2}{\partial x_i\partial x_j}u+{\Sigma }_i{b}_i\frac{\partial }{\partial x_i}u+cu$ be elliptic operators with Hölder continuous coefficients on a bounded domain $\Omega \subset {\mathbf{R}}^n$ of class $C^{1,1}$. There is a constant $c\>0$ depending only on the Hölder norms of the coefficients of $L$ and its constant of ellipticity such that $$c^{-1}{G}_{\Delta }^{\Omega }\le G_L^{\Omega }\le c{G}_{\Delta }^{\Omega }\text{on}\Omega \times \Omega ,$$ where ${\gamma }_{\Delta }^{\Omega }$ (resp. $G_L^{\Omega }$) are the Green functions of $\Delta$ (resp. $L$) on $\Omega$.

Some properties of the functions of the form $v\left(x\right)={\sum }_{i=0}^m{\left|x\right|}^i{h}_i\left(x\right)$ in ℝⁿ, n ≥ 2, where each $h_i$ is a harmonic function defined outside a compact set, are obtained using the harmonic measures.

A 2p-times continuously differentiable complex-valued function f = u + iv in a domain D ⊆ ℂ is p-harmonic if f satisfies the p-harmonic equation ${\Delta }^{p}f=0$, where p (≥ 1) is a positive integer and Δ represents the complex Laplacian operator. If Ω ⊂ ℂⁿ is a domain, then a function $f:\Omega \to {ℂ}^m$ is said to be p-harmonic in Ω if each component function $f_i$ (i∈ 1,...,m) of $f=(f₁,...,f_m)$ is p-harmonic with respect to each variable separately. In this paper, we prove Landau and Bloch’s theorem for a class of p-harmonic mappings...

On the set $ℝ$ of real numbers we consider a poset ${𝒫}_{\tau }\left(ℝ\right)$ (by inclusion) of topologies $\tau \left(A\right)$, where $A\subseteq ℝ$, such that $A_1\supseteq A_2$ iff $\tau \left(A_1\right)\subseteq \tau \left(A_2\right)$. The poset has the minimal element $\tau \left(ℝ\right)$, the Euclidean topology, and the maximal element $\tau \left(\varnothing \right)$, the Sorgenfrey topology. We are interested when two topologies ${\tau }_1$ and ${\tau }_2$ (especially, for ${\tau }_2=\tau \left(\varnothing \right)$) from the poset define homeomorphic spaces $(ℝ,{\tau }_1)$ and $(ℝ,{\tau }_2)$. In particular, we prove that for a closed subset $A$ of $ℝ$ the space $(ℝ,\tau (A\left)\right)$ is homeomorphic to the Sorgenfrey line $(ℝ,\tau (\varnothing \left)\right)$ iff $A$ is countable. We study also common...

In the study of spectral synthesis S-sets and C-sets (see Rudin [3]; Reiter [2] uses the terminology Wiener sets and Wiener-Ditkin sets respectively) have been discussed extensively. A new concept of Ditkin sets was introduced and studied by Stegeman in [4] so that, in Reiter’s terminology, Wiener-Ditkin sets are precisely sets which are both Wiener sets and Ditkin sets. The importance of such sets in spectral synthesis and their connection to the C-set-S-set problem (see Rudin [3])...

Dans une axiomatique des fonctions harmoniques un peu plus générale que celle de H. Bauer, on démontre les relations suivantes : $$R_{s+t}^A=R_s^A+R_t^A,$$ $$R_s^{A\cup B}+R_s^{A\cap B}\le R_s^A+R_s^B,$$ $$A_n\uparrow A,S_n\uparrow s\Rightarrow R_{s_n}^{A_n}\uparrow R_s^A,$$ où $A$, $B$, $A_n$, (resp. $s$, $t$, $s_n$) sont des ensembles (resp. fonctions hyperharmoniques non-négatives) arbitraires. Les mêmes relations sont valables pour $\widehat{R}$. On démontre aussi que la relation $${\int }^{*}sd{\mu }^A={\int }^{*}{\widehat{R}}_s^{A}d\mu$$ a lieu si l’espace de base a une base dénombrable ou si l’axiome $D$ de M. Brelot est satisfait,...