Banach space Lower semi-continuity (lsc) implying continuity

131 Views Asked by At

How to show the following:

If the monotone real valued function $f(x)$ whose domain is a subset of $R$ is lower semi continuous on every point of the interior of the domain then it is continuous on the interior of the domain.

Thank you!

2

There are 2 best solutions below

1
On BEST ANSWER

You can get a monotone counterexample by

$$f(x) = \begin{cases} x & x \le 0 \\ x+1 & x > 0\end{cases}$$

4
On

I don't think that's true. Take for example

$$ f(x)\colon [0,1] \to [0,1] \\ f(x)= \begin{cases} 1 \text{ if } x \neq 1/2 \\ 0 \text{ if } x=1/2 \end{cases} $$