Journal of Mathematical Analysis and Applications ( IF 1.2 ) Pub Date : 2021-04-26 , DOI: 10.1016/j.jmaa.2021.125270 J. Marshall Ash , Stefan Catoiu , William Chin
This article completes the more than a half a century old problem of finding the equivalences between generalized Riemann derivatives. The real functions case is studied in a recent paper by the authors. The complex functions case developed here is more general and comes with numerous applications.
We say that a complex generalized Riemann derivative implies another complex generalized Riemann derivative if whenever a measurable complex function is -differentiable at z then it is -differentiable at z. We characterize all pairs of complex generalized Riemann differences of any orders for which -differentiability implies -differentiability, and those for which -differentiability is equivalent to -differentiability. We show that all m points based generalized Riemann difference quotients of order n that Taylor approximate the ordinary nth derivative to highest rank form a projective variety of dimension for which an explicit parametrization is given.
One application provides an infinite number of equivalent ways to define analyticity. For example, a function f is analytic on a region Ω if and only if at each z in Ω, the limit exists and is a finite number. Four more applications relate the classification of complex generalized Riemann derivatives to analyticity and the Cauchy-Riemann equations, and to the theory of best approximations.
中文翻译:
复杂广义Riemann导数的分类
本文解决了一个半世纪以上的问题,即发现广义Riemann导数之间的等价关系。作者在最近的一篇论文中对实函数案例进行了研究。这里开发的复杂功能案例更为通用,并具有众多应用程序。
我们说一个复杂的广义黎曼导数 意味着另一个复杂的广义黎曼导数 如果每当有可测量的复杂函数 -在z处可微,那么它是-在z处可微分。我们表征所有对 任何阶的复杂广义黎曼差 -可区分性意味着 -可微性,以及那些 -可区分性等于 -可区分性。我们表明,所有米点数基于广义的顺序黎曼差商ň泰勒近似普通Ñ阶导数,以最高等级的形式投射各种尺寸的 为此,给出了明确的参数化。
一个应用程序提供了无数种等效的方法来定义分析性。例如,当且仅当在Ω中的每个z处有极限时,函数f才能在区域Ω上进行分析存在并且是一个有限数。另外四个应用程序将复杂的广义Riemann导数的分类与解析度和Cauchy-Riemann方程以及最佳逼近理论相关。