Conversation started Dec 13, 2011 at 20:22.
Dec 13, 2011 20:22
Does a basis for the uniform operator topology look like this? The set of all balls around all points T in B(X,Y) of all radii epsilon: $$\mathcal{B} = \bigcup_{T \in B(X,Y)} B_T(\varepsilon)$$ where $$B_T(\varepsilon) = \{ T^\prime \mid \sup_{\| f \| \leq 1} \| (T - T^\prime)f \| < \varepsilon} $$ for all $\varepsilon$ in $\mathbb{R}$?
the where case:
$$B_T( \varepsilon) = \{ \tilde{T} \mid \sup_{\| f \| \leq 1} \vert (T - T^\prime) f \vert < \varepsilon \} $$
That mod inside the sup expression should've been $\| \cdot \|_Y$
What you said in words is correct, but it's not what you wrote. $$\mathcal{B} = \{B_{\varepsilon}(T)\,:\,T \in B(X,Y),\,\varepsilon \gt 0\}$$ would be what I'd write.
I wanted to spell out the bit that tells me what the metric is. Because next I'm going to have to worry about a basis for the strong operator topology : )
Thanks, btw.
That was a typo. This $\bigcup \{ B_T (\varepsilon) \}$ is what I actually meant to write.
That's better :) However, you still don't bring all the $\varepsilon \gt 0$ into play.
Yeah just noticed when I wrote it down on paper.
Before worrying about the strong operator topology explicitly: given a vector space $X$ and a family $\mathscr{P}$ of semi-norms on $X$ can you write down a basis for the topology?
Dec 13, 2011 20:38
Here: $\bigcup_{\varepsilon > 0, T \in B(X,Y)} \{ B_T(\varepsilon )\}$
Now I'm happy.
By the way: are the balls really written like that in your class? It strikes me as odd to emphasize the radius more than the center. What I usually see is either $B_{r}(x)$ or $B(x,r)$.
No, I just made that up. I don't think it matters here.
How can a family of semi-norms induce a topology? I think I need to read some more before I answer your question.
The weakest topology that makes all the semi-norms continuous (the initial topology induced by the semi-norms).
Yes but I don't see how to write down a basis. Yet.
The strong operator topology, for instance, is the topology induced by the family $$\mathscr{P} = \{p_{x}\,:\,x \in X\}$$ where $p_{x}(T) = \|Tx\|_{Y}$.
Dec 13, 2011 20:45
Do anyone know any female mathematicians ?
@N3buchadnezzar Emmy Noether.
@N3buchadnezzar Right now, or historically?
Or rather, your favourite female mathematician would be a better question i guess
@Matt Every seminorm $p$ gives you a notion of balls with respect to $p$. A basis is given by finite intersection of such balls.
Dec 13, 2011 20:48
@N3buchadnezzar I am unfamiliar with the works of any other than Noether, and she's not my favourite.
@N3buchadnezzar Ulrike Tillmann, for example
I just feel like there are extremely few female mathematicians. And sadly I can hardly think of a single one
Time to study more
@N3buchadnezzar Check here
Curie is interesting, although she belongs to the branch of physicists
They don't have Marie-France Vigneras? That seems odd.
Dec 13, 2011 20:51
Isn't she a bit young to have a biography there?
too old
grins
She's not young.
Probably about as old as Dusa McDuff.
I'd have guessed around 60, yes. Maybe a bit more. Anyway, the list is far from complete.
Of course.
I'm starting to like all that "Further reading material" links.
Dec 13, 2011 20:55
I started by looking for number theorists.
I'm going now. Goodnight.
Good night, Asaf!
Bye Asaf!
G'night.
Dec 13, 2011 21:23
I think there is a typo in the lecture notes. They define the strong operator topology on $B(X,Y)$ to be the weakest topology for which the evaluation map $L \mapsto Lx$ is continuous for every $x$. It should be $L \mapsto \| Lx \|_Y$ for the norm on $Y$. But then there is only one norm and no family of semi-norms.
Puppy stroll time. Brb.
Both descriptions are correct. Note that the semi-norm $L \mapsto \|Lx\|_Y$ depends on $x \in X$.
Dec 13, 2011 21:48
And where is the family of semi-norms? $\| \cdot \|_Y$ is just one (non-semi) norm.
\usepackage{mathtools} is perhaps preffered?
@Matt $\{|L|_x = \|Lx\|_Y\,:\,x \in X\}$
@tb Oh. I misunderstood what this means. : ( Thank you!
 
Conversation ended Dec 13, 2011 at 21:52.