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arXiv 2001.00523math.AP
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无时间正则算子半群的一致收敛性

Uniform convergence of operator semigroups without time regularity

Alexander Dobrick, Jochen Glück

摘要:

当我们对线性发展方程解的长期行为感兴趣时,我们可以利用$C_0$ -半群理论中的大量技术。然而,如果我们考虑例如在$\mathbb{R}^d$上具有无界系数的抛物型方程,则解半群一般不会是强连续的。对于这样的半群,许多工具,可以用来研究的渐近行为的$C_0$ -半群是不可用的了,因此,更少的是知道他们的长期行为。基于这一观察,我们证明了一般半群表示的算子范数收敛的新特征-没有任何时间正则性假设-通过适应M.~哈塞和第二个署名作者。除了其独立的时间规律性,我们的方法也允许我们处理离散时间的情况下(即,单个算子的幂)以及在同一统一设置中的更抽象的半群表示。作为应用,我们证明了具有上述性质的抛物型方程解的一个收敛定理。

英文摘要:

When we are interested in the long-term behaviour of solutions to linear evolution equations, a large variety of techniques from the theory of $C_0$-semigroups is at our disposal. However, if we consider for instance parabolic equations with unbounded coefficients on $\mathbb{R}^d$, the solution semigroup will not be strongly continuous, in general. For such semigroups many tools that can be used to investigate the asymptotic behaviour of $C_0$-semigroups are not available anymore and, hence, much less is known about their long-time behaviour. Motivated by this observation, we prove new characterisations of the operator norm convergence of general semigroup representations - without any time regularity assumptions - by adapting the concept of the "semigroup at infinity", recently introduced by M.~Haase and the second named author. Besides its independence of time regularity, our approach also allows us to treat the discrete-time case (i.e., powers of a single operator) and even more abstract semigroup representations within the same unified setting. As an application of our results, we prove a convergence theorem for solutions to systems of parabolic equations with the aforementioned properties.

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