MATH 0017 - Measure Theory Homework 8
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MATH 0017 - Measure Theory
Homework 8
Question 8.1. (i) Suppose g : R → [0, o) is measurable and vanishes (equals 0) outside a bounded interval and that R g2 dλ。 < o. Prove that R g dλ。 < o also. (Here λ。 is the Lebesgue measure on R.)
(ii) Suppose f : R → [0, o) is measurable and R f dλ。 < o. For any a > 0, let the super-level set Ea = {x e R } f (x) > a(. Prove
λ。(Ea ) < 1 f dλ。.
Question 8.2. Let (X, A, µ) be a measure space and {fn (n1。(二) c LI (X, A, µ). Suppose fn decreases pointwise to f and that f。dµ < o. Prove that f dµ = limn→二 fn dµ .
Question 8.3. (i) Let (X, A, µ) be a measure space and {fn (n1。(二) c LI (X, A, µ). Suppose
f → f pointwise and that f dµ = limn→二 fn dµ < o. Prove that, for all E c A, E f dµ = limn→二 E fn dµ .
(ii) Give a counterexample to show that this may fail if f dµ = limn→二 fn dµ = o.
2022-12-09