Is f Measurable if E is a Measurable Set of Measure Zero?

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SUMMARY

If E is a measurable set of measure zero and f is a bounded function on E, then f is indeed measurable. The proof hinges on demonstrating that the sets f^{-1}(m, ∞) and f^{-1}(-∞, M) are measurable, as they are inverses of Borel sets (intervals). The discussion clarifies that the focus is on Lebesgue measurability, confirming that every subset of a measure zero set is measurable.

PREREQUISITES
  • Understanding of Lebesgue measure and its properties
  • Knowledge of Borel sets and their significance in measure theory
  • Familiarity with measurable functions and their definitions
  • Basic concepts of set theory and intersections
NEXT STEPS
  • Study the properties of Lebesgue measurable functions in detail
  • Explore the relationship between Borel sets and Lebesgue measure
  • Investigate the implications of measure zero sets in real analysis
  • Learn about the concept of measurable sets and their applications in probability theory
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Mathematics students, particularly those studying real analysis and measure theory, as well as educators and researchers interested in the properties of measurable functions and sets.

sbashrawi
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Homework Statement


If E is a measurable set of measure zero, and f is bounded function on E. Is f measurable?

I tried to prove this by saying that E = { x in E | m< f(x) <M}
= {x in E | f(x) > m }intersecting { x in E | f(x) < M } and these are measurable
so f is measurable. Am I right ?


Homework Equations





The Attempt at a Solution

 
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This is true as far as it goes, but you need to say specifically why the sets f^{-1}(m, \infty) and f^{-1}(-\infty, M) are measurable sets.
 
They are measurable since they are inverses of borel sets ( intervals)
 
In you original post: Are you talking about Borel measurability or Lebesgue measurability?
 
I mean lebesgue measure
 
sbashrawi said:
They are measurable since they are inverses of borel sets ( intervals)

This is what you are asked to prove. You need to give a specific argument from the hypotheses why they are measurable sets.
 
sbashrawi said:
I mean lebesgue measure

But the isn't every subset of of a set of measure zero measurable?
 

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