« first day (4182 days earlier)      last day (1136 days later) » 

23:01
You just have to find convexity even when it isn't there.
How do you write weak closure in MathJax?
I don't like $\text{cl}_w$ sort of things
How do you write it not in MathJax?
$\overline{A}$ but with a little $w$ at the end of the bar.
Oh, I'm sure we can do that in MathJax.
Not critical of course.
23:13
But perhaps it would be easiest just to define it in words and use a different symbol :)
I've built more complicated macros than that in LaTeX.
I eschew complication nowadays
So just say it in words and call it by a different font or different letter.
I'm fond of \mathscr :)
there are some really random convexity results in functional analysis. here's one. if X is a banach space, and not reflexive, then X'''' is not strictly convex. ' denoting continuous dual.
This reminds me of triple perps for subspaces.
We got a slick proof in our linear algebra exercises using those. I suppose I could find it.
i think four is where i've seen dual banach spaces top out. if someone finds a paper with five duals, let me know.
23:26
Right. For every subspace (this is finite-dimensional in our book, but I expect it holds in infinite dimensions as well) $V^\perp = \big((V^\perp){}^\perp\big){}^\perp$.
yeah. perp perp is closure, and perps are closed.
Yup.
I think we actually used that for something in some subsequent exercise, but ... I dunno.
X'' is the closure of X in the weak or strong operator topology, with X a subalgebra of operators on hilbert space and ' denoting commutant. lots of closure-like operators around.
someone should start a religion around this.
@copper It probably suffices for you to do $\overline A{}^w$.
Oh, interesting, it works better in LaTeX than in MathJax.
@TedShifrin Thanks, that is good
having stupid windows problems trying to copy a file "Can’t read from the source file or disk". idiot syttem.
23:37
hah, i had some fun with the local network. the client sent us files that expanded into pathnames that were too long for windows (which tops out before 300 characters). windows let our IT people create those files/paths but once they're created you can't open them.
It could never be that it's the idiot operator ...
That's a very intelligent catch-22 loophole.
i was apparently the first to flag this issue despite us having received the files a week ago.
about which the less said, the better.
@copper I just saw the post you used that. I would do the overline just on $S$, not including the $x_0$.
I would also do $\bigcap$ rather than $\cap$ :P
But I'm done kibbitzing.
you also can't rename them, which is funny, because that's what's wrong with it.
i do wonder how windows lets itself create files that can never be spoken of again.
If you have an inaccessible file, you can't access it to rename it. Seems right to me.
In MacOS I can rename things willy-nilly, I think.
I bet if you go into the right Unix mode, you can rename it, @leslie.
23:41
i don't have access to the command line as a mere employee.
the client's files were in that state because whoever runs their document management system is just crazy.
Wow, I just had my most miserable interview in 5 years of interviewing prospective admitees. So painfully shy. It was beyond pulling teeth.
lots of empty folders, or folders with no contents other than another folder. all hand-named variations of "Working" and "Temp" and "Random".
Can't your IT people get access to rename it, @leslie?
yeah, they fixed the stuff i was going after. they are hesitant to change anything from the form/format the client gave us for legal reasons so i had to really spell out what it was OK for them to do and not do in the email.
Well, it wouldn't be good if they opened the files and changed the content.
23:43
even metadata can sometimes be an issue, such as filenames. i made clear, please create a new local copy, don't fiddle with the original. that smoothed things over.
Ah, that's cool.
i've never had an interview where shyness was the problem. usually the opposite was the problem.
older people, though.
Usually, my interviews run comfortably 75-90 minutes. Today, I gave up at 48.
Some prospective college students pad their lives with too many clubs, volunteer things, summer internships. But this student had basically zero.
hah, that would have been me. my only activity was co-running a club that i created, and in a field (chemistry) that i was not interested in going into.
i think that came up in my interviews.
thankfully there are schools that don't do interviews.
Just a weird juxtaposition. Two days ago I had one of the two strongest interviews ever (I think).
23:48
one time i interviewed a guy who had a really stellar resume, but he couldn't say even the first thing about any of his experiences. and he should have been able to. e.g. interning for a senator. meeting two presidents. it gave the impression that maybe it was all a ruse and he had made it all up.
it was really weird, because usually people with even one of those qualifications can't stop talking about them.
@TedShifrin Thanks, I took your suggestions.
Yeah, most of the time my interviewees are smart enough to have one or two questions prepared for me. Not too hard to think of a few things to ask an alumnus. This kid didn't have anything.
it could be something where a family member made them apply, or something. i bet a lot of that goes on.
23:51
No, I asked that. There was a reason.
weird
my dad made me apply to a bunch of small liberal arts schools. he had a romantic notion of them despite not having gone to one.
i usually as too many questions
despite, or perhaps because of.
When even the ones I am impressed by don't get in, there isn't too much hope for the ones I say shouldn't be admitted.
uc santa cruz discrete math has the students grade other students
is that normal?
23:52
my wife's family made her apply to most of the ivy league. i don't know why.
That's cuz they don't have money to hire a grader.
i am not sure what they are doing with my money then
that is a UCSC thing. that is 100% on brand for UCSC. except maybe the part about having 'grades.' what is this, nazi germany?
The math department (or whatever) is not seeing your money. Trust me.
23:53
my daughter's setup is similar in price but she does not grade
UGA adminstration didn't believe in hiring undergraduate graders.
it is probably good for him, but i am on the fence about his education in general
berkeley had funding for graders some, but not all of the time. it was always an open question at the beginning of the year, whether your stuff would be graded. and by whom.
Well, one does learn a lot by grading. Presumably, each student grades one fellow student's paper. It's a little awkward if it's a friend.
they don't see names and they only grade some subset of questions
23:54
one summer i was taken off of grading for an analysis class because the instructor, all of two years my senior, didn't want an undergrad grading for his class. i hope he did it himself.
We did dig up money out of unrestricted funds to hire a few undergraduate graders. Mostly grad students were way worse as graders.
but i would have been peeved if was paying for an education and had to grade
i remember that guy's name and if i saw him today i would probably kick him.
I think some students might like it as part of the class experience, seriously, copper.
now copper is going to give us his rant about bagging groceries in the self checkout. "i don't recall applying to work here," etc.
23:56
However, if I got badly evaluated by my fellow student (i.e., the grading was incompetent), the instructor would see me immediately in his office.
LOL: three points for @leslie.
i usually bag. outside of the usa i think that is typical
it's a great custom. in produce that is paid by quantity instead of weight they let you type in how much you should pay.
at iowa when i didn't have a grader i'd tell people to just handwrite anything they wanted me to check on the tops of their assignments. of course, only the A students actually did that, and of course they were right every time.
there are good things to be said for students evaluating work. it helps you understand what your own work looks like.

« first day (4182 days earlier)      last day (1136 days later) »