Compact sets of continuity for Borel functions
نویسندگان
چکیده
منابع مشابه
Ideals of compact sets associated with Borel functions
We investigate the connection between the Borel class of a function f and the Borel complexity of the set C(f) = {C ∈ J(X) : f |C is continuous} where J(X) denotes the compact subsets of X with the Hausdorff metric. For example, we show that for a function f : X → Y between Polish spaces; if C(f) is Fσδ in J(X), then f is Borel class one.
متن کاملCompact Sets of Functions and Function Rings
A widely used theorem of analysis asserts that a uniformly bounded, equicontinuous family of functions has a compact closure in the space of continuous functions. This lemma, variously attributed to Arzela, Escoli, Montel, Vitali, and so on, is of importance in the theory of integral equations, conformal mapping, calculus of variations, and so on. In recent years the lemma has been generalized ...
متن کاملNon-decreasing Functions, Exceptional Sets and Generalised Borel Lemmas
The Borel lemma says that any positive non-decreasing continuous function T satisfies T (r+1/T (r)) ≤ 2T (r) outside of a possible exceptional set of finite linear measure. This lemma plays an important role in the theory of entire and meromorphic functions, where the increasing function T is either the logarithm of the maximum modulus function, or the Nevanlinna characteristic. As a result, ex...
متن کاملUniform Continuity of Continuous Functions on Compact Metric Spaces
A basic theorem asserts that a continuous function on a compact metric space with values in another metric space is uniformly continuous. The usual proofs based on a contradiction argument involving sequences or on the covering property of compact sets are quite sophisticated for students taking a first course on real analysis. We present a direct proof only using results that are established a...
متن کاملEvents of Borel Sets, Construction of Borel Sets and Random Variables for Stochastic Finance
We consider special events of Borel sets with the aim to prove, that the set of the irrational numbers is an event of the Borel sets. The set of the natural numbers, the set of the integer numbers and the set of the rational numbers are countable, so we can use the literature [10] (pp. 78-81) as a basis for the similar construction of the proof. Next we prove, that different sets can construct ...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
ژورنال
عنوان ژورنال: Topology and its Applications
سال: 2008
ISSN: 0166-8641
DOI: 10.1016/j.topol.2008.05.001