Can a Subsequence of Measurable Functions Converge in L1?

  • Thread starter Thread starter Funky1981
  • Start date Start date
  • Tags Tags
    Type
Funky1981
Messages
21
Reaction score
0

Homework Statement



Let fn be a sequence of measurable functions converges to f a.e. Is it possible to get a subsequence fnk of fn s.t. fn converges in L1 ?

2. The attempt at a solution
I have proved the converse statement is true and i guess the above statement is impossible but I fail to prove it.
 
Physics news on Phys.org
Hint: Look for a counterexample where ##f_n \rightarrow 0## pointwise but ##\|f_n\| = 1## for all ##n##.
 
Thanks for your suggestion
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
Back
Top