Tuesday 15 September 2015

lebesgue measure - Continuous function with derivative a.e. and Luzin N property is absolutely continuous



Let $f:I\rightarrow\mathbb{R}$ be a continuous function which derivative exists a.e. and $\int f'$ exists in I. Also, suppose $f$ satisfies the Luzin N property. Show that $f$ is absolutely continuous.



So I don't seem to find any way to tackle this problem. This seems to be covered everywhere when the derivative is defined everywhere, but no such case when it's only a.e.



What I know is that using bounded variation it's possible to get absolute continuity, however I can't find how to prove the bounded variation condition.



Is there a reference or a way to solve this problem?


Answer




See 2. here. The theorem that's being proven assumes bv, but that condition is only used to establish that $f$ has a derivative a.e. that is integrable, which are exactly the conditions you have.


No comments:

Post a Comment

real analysis - How to find $lim_{hrightarrow 0}frac{sin(ha)}{h}$

How to find $\lim_{h\rightarrow 0}\frac{\sin(ha)}{h}$ without lhopital rule? I know when I use lhopital I easy get $$ \lim_{h\rightarrow 0}...