Decomposing Borel sets and functions and the structure of Baire class 1 functions
نویسندگان
چکیده
منابع مشابه
Decomposing Borel Sets and Functions and the Structure of Baire Class 1 Functions
All spaces considered are metric separable and are denoted usually by the letters X, Y , or Z. ω stands for the set of all natural numbers. If a metric separable space is additionally complete, we call it Polish; if it is a continuous image of ω or, equivalently, of a Polish space, it is called Souslin. The main subject of the present paper is the structure of Baire class 1 functions. Recent de...
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The following two theorems give the flavour of what will be proved. THEOREM. Let Y be a complete metric space. Then the families of first Baire class functions and of first Borel class functions from [0, 1] to Y coincide if and only if Y is connected and locally connected. THEOREM. Let Y be a separable metric space. Then the families of second Baire class functions and of second Borel class fun...
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In 1990 Kechris and Louveau developed the theory of three very natural ranks on the Baire class 1 functions. A rank is a function assigning countable ordinals to certain objects, typically measuring their complexity. We extend this theory to the case of Baire class ξ functions, and generalize most of the results from the Baire class 1 case. We also show that their assumption of the compactness ...
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ژورنال
عنوان ژورنال: Journal of the American Mathematical Society
سال: 1998
ISSN: 0894-0347,1088-6834
DOI: 10.1090/s0894-0347-98-00269-0