Let $(X,\|\cdot\|_1)$ and $(X,\|\cdot\|_1)$ be Banach spaces. Does it imply that $\|\cdot\|_1-\|\cdot\|_2$ (equivalent)?
It is know that if $\|\cdot\|_1-\|\cdot\|_2$ and $(X,\|\cdot\|_1)$, then $(X,\|\cdot\|_1)$ is also Banach space.
I actually want to prove that $(C[0,1],\|\cdot\|_{L^1}$ is not Banach space.
How can we prove the last statement? Is there any counterexample or we need to prove directly by using Cauchy sequence?
$\sim$
would be better? – Martin Sleziak Jul 06 '14 at 10:59