Annali di Matematica Pura ed Applicata ( IF 1 ) Pub Date : 2020-09-02 , DOI: 10.1007/s10231-020-01030-0 Giovanni Cupini , Ermanno Lanconelli
Let D be an open subset of \({\mathbb {R}}^n\) with finite measure, and let \(x_0 \in D\). We introduce the p-Gauss gap of D w.r.t. \(x_0\) to measure how far are the averages over D of the harmonic functions \( u \in L^p(D)\) from \(u(x_0)\). We estimate from below this gap in terms of the ball gap of D w.r.t. \(x_0\), i.e., the normalized Lebesgue measure of \(D \setminus B\), being B the biggest ball centered at \(x_0\) contained in D. From these stability estimates of the mean value formula for harmonic functions in \(L^p\)-spaces, we straightforwardly obtain rigidity properties of the Euclidean balls. We also prove a continuity result of the p-Gauss gap in the Sobolev space \(W^{1,p'}\), where \(p'\) is the conjugate exponent of p.
中文翻译:
Lebesgue空间中调和函数均值公式的稳定性
设D为具有有限度量的\({\ mathbb {R}} ^ n \)的开放子集,并设\(x_0 \ in D \)。我们引入p -高斯缺口的d WRT \(X_0 \)来衡量多远超过平均值d的调和函数\(U \在L ^ P(d)\)从\(U(X_0)\)。我们从该间隙以下以D wrt \(x_0 \)的球间隙来估算,即\(D \ setminus B \)的归一化Lebesgue度量,它是B以\(x_0 \)为中心的最大球包含在D中。从这些对\(L ^ p \)-空间中谐波函数的平均值公式的稳定性估计中,我们可以直接获得欧几里得球的刚度性质。我们还证明了Sobolev空间\(W ^ {1,p'} \)中p -Gauss间隙的连续性结果,其中\(p'\)是p的共轭指数。