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arXiv math/0305331math.FAmath-phmath.MP
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索伯列夫空间中的定量谓词演算

Quantitative functional calculus in Sobolev spaces

Carlo Morosi, Livio Pizzocchero

摘要:

在Sobolev(Bessel势)空间$H^n(\reali^d, \reali {or} \complessi)$的框架下,考虑非线性Nemytskij算子将函数$x \in \reali^d \mapsto f(x)$变换为复合函数$x \in \reali^d \mapsto G(f(x), x)$ .假设$G$足够光滑,我们给出了一个“驯服”的约束上的$H^n$范数的复合函数的$H^n$范数的$f$的一个线性函数,系数取决于$G$和$H^a$范数的$f$,对于所有整数$n, a, d$与$a > d/2$。在与以前的结果在这个问题上,我们的界限是完全明确的,允许定量估计的$H^n$规范的功能$x \mapsto G(f(x),x)$。当应用到$G(f(x), x) = f^2(x)$的情况下,这个界限同意我们以前的结果在索伯列夫空间的函数的逐点积。

英文摘要:

In the framework of Sobolev (Bessel potential) spaces $H^n(\reali^d, \reali {or} \complessi)$, we consider the nonlinear Nemytskij operator sending a function $x \in \reali^d \mapsto f(x)$ into a composite function $x \in \reali^d \mapsto G(f(x), x)$. Assuming sufficient smoothness for $G$, we give a "tame" bound on the $H^n$ norm of this composite function in terms of a linear function of the $H^n$ norm of $f$, with a coefficient depending on $G$ and on the $H^a$ norm of $f$, for all integers $n, a, d$ with $a > d/2$. In comparison with previous results on this subject, our bound is fully explicit, allowing to estimate quantitatively the $H^n$ norm of the function $x \mapsto G(f(x),x)$. When applied to the case $G(f(x), x) = f^2(x)$, this bound agrees with a previous result of ours on the pointwise product of functions in Sobolev spaces.

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