my question is probably rather simple I just never came across this notation:
$sup\{||f-f(\bullet-y)||: f\in K\}\rightarrow 0$ and I cannot realy seem to find what it indicates. I am guessing it means something in the sense of
$sup\{||g||: g(x)=(f(x)-f(x-y)) \forall x; f\in K||\}\rightarrow 0$
Does anybody know this notation and can verify or clarify this for me? If it makes a difference: The notation came across while looking into Sobolev Spaces.
Thankyou very much!