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arXiv 1412.4151math.FAmath.APmath.CA
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由$j$ -椭圆泛函生成的非线性半群

Nonlinear semigroups generated by $j$-elliptic functionals

Ralph Chill, Daniel Hauer, James B. Kennedy

摘要:

我们推广的能量泛函理论用于梯度系统的研究的情况下,域的定义的功能不能嵌入到希尔伯特空间$H$上的相关运营商的行为,如当$H$是一个跟踪空间。我们表明,在较弱的条件下的功能$φ$和$j$从$φ$的有效域的$H$,这在反对经典理论不一定是内射,甚至连续的$H$上的运营商自然与对$(φ,j)$,但产生一个非线性半群的压缩$H$。我们表明,这个运营商,我们称之为$j$ -次梯度的$φ$,是(经典)次梯度的另一个功能的$H$,并给出了广泛的特点,这个功能方面的$φ$和$j$。在$H$是$L^2$ -空间的情形下,我们还利用$φ$和$j$证明了半群的正性、$L^\infty$ -压缩性和对$L^q$的保序外推的存在性.这个理论是通过大量的例子来说明,包括$p$ -Dirichlet-诺依曼算子,一般罗宾型抛物边值问题的$p$ -Laplacian非常粗糙的区域,和某些耦合抛物椭圆系统。

英文摘要:

We generalise the theory of energy functionals used in the study of gradient systems to the case where the domain of definition of the functional cannot be embedded into the Hilbert space $H$ on which the associated operator acts, such as when $H$ is a trace space. We show that under weak conditions on the functional $φ$ and the map $j$ from the effective domain of $φ$ to $H$, which in opposition to the classical theory does not have to be injective or even continuous, the operator on $H$ naturally associated with the pair $(φ,j)$ nevertheless generates a nonlinear semigroup of contractions on $H$. We show that this operator, which we call the $j$-subgradient of $φ$, is the (classical) subgradient of another functional on $H$, and give an extensive characterisation of this functional in terms of $φ$ and $j$. In the case where $H$ is an $L^2$-space, we also characterise the positivity, $L^\infty$-contractivity and existence of order-preserving extrapolations to $L^q$ of the semigroup in terms of $φ$ and $j$. This theory is illustrated through numerous examples, including the $p$-Dirichlet-to-Neumann operator, general Robin-type parabolic boundary value problems for the $p$-Laplacian on very rough domains, and certain coupled parabolic-elliptic systems.

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