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arXiv 1206.0795math.LOmath.GN
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关于有限级和ω-可分解Borel函数的结构

On the structure of finite level and ω-decomposable Borel functions

Luca Motto Ros

摘要:

本文给出了包含所有有限级Borel函数类的结构的完整描述,并给出了一个众所周知的事实的初等证明,即不是每个Borel函数都可以写成n ^0_α-可测函数的可数并(对每个固定的1个\leq α< ω_1).此外,我们提出了一些结果,这些Borel函数是ω-分解成连续函数(也称为可数连续函数在文献中):这些结果应被视为一个贡献的目标推广到所有有限水平的显着定理的Jayne和Rogers,事实上,他们允许我们证明这样的推广的一些限制形式。我们还分析了有限级Borel函数的组成方面的简单功能,我们最后提出了一个应用到巴拿赫空间理论。

英文摘要:

We give a full description of the structure under inclusion of all finite level Borel classes of functions, and provide an elementary proof of the well-known fact that not every Borel function can be written as a countable union of Σ^0_α-measurable functions (for every fixed 1 \leq α< ω_1). Moreover, we present some results concerning those Borel functions which are ω-decomposable into continuous functions (also called countably continuous functions in the literature): such results should be viewed as a contribution towards the goal of generalizing a remarkable theorem of Jayne and Rogers to all finite levels, and in fact they allow us to prove some restricted forms of such generalizations. We also analyze finite level Borel functions in terms of composition of simpler functions, and we finally present an application to Banach space theory.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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