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9:02 PM
@QED 0 having no reciprocal is the short and overly laconic answer to this entire question about division by 0, so what better way to end the endless "why, why, why... " than to prove 0a = 0? Professor
 
QED
yes
I agree but the post is so long that it's easy to lose track
of what's being said
 
@tb You have Glendronach?
 
@QED Do you have any suggestions on how to shorten it so that what's being said is not being lost track of Professor?
 
QED
you could try to but it's not important
 
@QED Thank you once again for your time and attention Professor
 
9:11 PM
@QED How does it feel to be called professor?
 
Poor me, Banach limits aren't mentioned in Kreyszig : S
 
@Matt Of course not!
 
@JonasTeuwen: Why is that obvious?
 
QED
dishonest
 
@Matt That book is too elementary.
 
9:13 PM
Oh, it was converted to a png: i.stack.imgur.com/4AfRR.png
@Matt I created a PDF using Intaglio but it was converted to a PNG upon upload.
 
@robjohn: This time using pencil tool?
 
As a PDF it would be resolution independent.
 
For iPhone I need png... or pvr
 
@Matt No, I played with blocks :-)
 
@robjohn: if you set pencil to one pixel it's the same : )
 
9:17 PM
I put together red squares.
 
@JonasTeuwen: My level is elementary.
 
Are you Dr. Watson?
 
@Matt Then why do you want to know about Banach limits?
 
@robjohn: That's what I did in AI : )
 
No, I moved around big red squares and put them where they should go. Much better than the pencil. I could have just drawn the outline.
 
9:18 PM
@JonasTeuwen: Because my homework asks me to. : ( I'll never improve if I have to keep on solving stuff that I have no clue about : S
 
@Matt Oh the concept is quite easy.
 
@robjohn: Don't worry, I'm not going to rant anymore.
 
My girlfriend doesn't like whisky. Yey! More for me!
2
 
Hah.
Mine does not like arak.
 
@JonasTeuwen: According to wikipedia it's just a continuous linear functional. So yes, the concept might be easy.
 
9:22 PM
@AsafKaragila Not surprising.
 
Of course.
 
Ack! I just realized there were two Matts, each with the same pseudonym.
 
Was this your cat stepping on your keyboard? : )
 
No that was something laying on my keyboard.
 
A cat, by any chance?
 
9:28 PM
@AsafKaragila Not a cat. The kitten is napping and our cats are elsewhere as well.
 
I see.
 
That reminds me: I need to call the vet. It has been 2 weeks, and they wanted to see the kitten after 2 weeks.
 
It is about time, then.
 
Is it sick?
 
It is about time; I am calling now. It is not sick.
Now they say they don't need to see her for 4 weeks.
The poor kitten is going stir-crazy in the crate she is in. She wants out, but we can only take her out to hold her or clean her crate.
 
9:34 PM
?? Why is that?
 
She has to be kept as quiet as possible until her pelvis heals.
We found her on the street, dragging herself to the curb with her front feet.
 
Aaaawww : (
 
We had to stop all the traffic (just a few cars) and get her into a box to take to the vet.
 
Will she walk again? Or has the spine been damaged?
 
When we first got there, they said that the spine had probably been crushed (assuming it was hit by a car) so we should just euthanize it. But I said that we didn't bring it in just to be put down, so we insisted on x-rays.
Apparently the spine was fine, but one side of the pelvis was broken. However, cats heal bone injuries well, so the prognosis is good.
She is trying to climb everywhere despite our best efforts to keep her quiet.
 
QED
9:39 PM
quiet?
 
You're nice! Good job. Sad thing about the story is: it proves that people are incompetent and unless you do all the thinking yourself, jobs don't get done properly : (
 
It's been 2 weeks (today) since we found her. The vets said that we should keep her crated for 4 weeks for her to heal.
@QED not moving around much so that the bones can heal.
@QED we don't have a kitten ball-gag or anything :-p
 
QED
hehe
 
@Matt I think that they wanted to make it easy for us to back out, if we needed a way to back out.
I don't think they were being incompetent.
 
QED
9:58 PM
ah
the difference between PA and PRA is that you can't prove strong induction from induction?
 
Well, I went ahead with my threat to find a question of my own to ask, after our lament about the poor quality of recent questions. It remains to be seen whether this is an improvement. :)
 
Hi Mike.
 
Hi @Asaf.
 
How's you?
 
Fine - enjoying a beautiful but cold Saturday afternoon. And yourself?
 
10:06 PM
Tired, sleep soon.
 
QED
what is the difference between PA and PRA?
 
Peano Arithmetics, and Peano REAL Arithmetics?
 
QED
primitive recursive arithmetic
 
QED
the proof theoretic ordinal of PA is epsilon_0 and PRA is omega^omega
I'm trying to understand why
 
10:14 PM
What is the difference in the theories?
 
QED
PRA doesn't have quantifiers
so I can't let P(n) = forall k, k < n -> R(k) and use induction on P to prove strong induction on R
 
Hmmm.
 
QED
but there might be another way to prove it, encoding lists into numbers.. or something. I could be barking up the wrong tree with thinking about "strong induction"
 
@MikeSpivey Let's hope the question is not migrated to stats.SE =)
 
@QED: I'd assume that the sentences that you can write like that are lower in the arithmetic hierarchy.
 
10:20 PM
@Srivatsan That is a possibility. :) And maybe I should have asked it there; however, like I said, it was partly in response to me saying that I would look for questions of my own to ask here.
 
QED
yes
 
I do think it's on-topic here, though. Usually only the more advanced stats questions get migrated.
 
@MikeSpivey Well, I am ok with the question staying here/going to stats. I pointed it out because I knew you wanted to ask a question in Math.SE after the recent spike in low-quality posts.
 
@Srivatsan Part of my problem with asking questions on math.SE is that many of the questions I'm interested in would probably get better answers on MO.
 
@MikeSpivey Um... That is an issue, yes.
 
10:26 PM
I'm going to keep looking for questions, though. I don't like complaining about something but not doing anything about it.
Not that me asking a few questions is going to dramatically raise the quality. But it's the only thing I can think of to do about it.
 
Good questions will be a moral boost anyways. So please do look.
 
If only I had a good question to ask.
My last two MO question got >15 votes, though :-P
 
I had some homework questions (in combinatorics et al) a few weeks back.
I remember thinking they were good, but don't remember the questions.
I somehow haven't got the art of asking questions that might interest a researcher.
 
Another part of my problem is that for some of my interest areas, like optimization and linear programming, I am by far the most active user on math.SE in that area. There wouldn't be much point in me asking questions about those topics here. Those should get asked at MO or CS Theory.
 
Much like I can't ask about AC here :-D
 
10:31 PM
How about challenge problems? =)
 
@AsafKaragila Yes. :) I bet many of the top users have a topic or two like that.
 
@AsafKaragila What are you bragging about? You don't even know what AC means, I am sure... =)
 
Hah. I have more choice than you can ever imagine, Hindu dude. I just choose not to use it.
 
@Srivatsan I did ask one of those about a year ago and got some good responses. I've been hesitant to ask those, though, because the community hasn't always supported them.
 
Hindu dude... I was waiting for the day when Asaf would throw some abuses in my direction. Without it, somehow I don't feel I like I belong in this chatroom.
 
10:34 PM
I've had some great responses here to "I know one way to do or prove X; does anybody know other ways?" I might look for some of those.
 
@Srivatsan 20/11/2011
Call that karma :-P
 
@AsafKaragila And whom did you abuse on 11/11/11? :D
 
@MikeSpivey That was nine days ago. How should I remember??
 
Sleepy time here. Good night folks!
 
G' Night, Matt.
 
10:54 PM
@Srivatsan: Well, I got at least one good response already to my question.
 
Which one?
Oh one sec.
Um, interesting.
This paradox is actually pretty subtle, yes. I cannot intuitively see any of the examples... :)
 
I am slightly irritated that he didn't read my question carefully enough to notice that one of his examples was already in the question. But the new example was good enough that overall I gave him +1.
 
It was a little hard to find, Mike.
I do remember reading that your question mentioned batting, but it still took some time for me to locate it the second time.
 
@Srivatsan Yes, it is, which is why it's so hard to spot. The gender bias example is great. Berkeley was sued in the 1970s because women were being admitted to graduate school at a lower rate than men. The university successfully defended itself by pointing out that when you broke the data down by department, women were being admitted at the same or higher rates than men. The underlying and not immediately apparent explanation was that women tended to apply to more competitive departments.
So the women's overall rate was more heavily weighted by the more competitive departments, and the men's overall rate was more heavily weighted by the less competitive departments. This caused the men's overall acceptance rate to be higher, despite being generally lower at the department level.
@Srivatsan Maybe I should cut him some slack, then. But my comment still stands: He did repeat one of the examples in my question.
 
Yes, that he repeated the example is a fact. Not disagreeing with it.
 
11:16 PM
I see Henning is progressing smoothly with his quest to eliminate the "differential" tag.
 
@MikeSpivey I guess that was the main idea of my only question. "I can prove it backwards, can anyone prove it forwards?"
 
A possible counterargument could be that Berkeley was implicitly discriminating by making fewer openings (what's the correct word here?) available in subjects that women want to study, thereby causing them to be more competitive.
@MikeSpivey There are 5 left now, to be done tomorrow. Two of the latest batch actually had something to do with differentials; that's a first,
Nothing about mechanical engineering yet, sadly.
 
@HenningMakholm My car keeps sliding to the left even when I steer to the right. Could there be something wrong with my differential?
@HenningMakholm You beat me to it :-p
 
@HenningMakholm I think the problem was that the departments that women tended to apply to just had a lot more applicants, like humanities programs, so their acceptance rates were lower. It wasn't that there were fewer openings - well, there were fewer relative openings, but that isn't quite the same thing.
@robjohn And your question got some good responses, too, if I do say so myself. :)
 
@MikeSpivey The batting scores were second in line, and so easy to miss. Don't be too irritated.
@MikeSpivey I am extremely pleased with all the answers, even if I do say so myself :-)
 
11:28 PM
@robjohn I said I was only slightly irritated. :) But I accept yours and Srivatsan's reprimands (?) and will cut Mr. Hardy some slack there. Besides, he did give me one new good example I was unaware of, which is what I was after by asking the question.
 
@MikeSpivey It's not by any means a decisive argument (and I don't personally think it ought to carry the day), but one might still argue that if the university is supposed to size its departments according to student demand, then the disparity indicates that it must have been more responsive to demand in areas favored by men than in areas favored by women. The premise that I've emphasized here is perhaps not easily established, but that can conceivably be hidden away by clever rhetorics.
 
Well. I think I better go on and take a nap for a few hours.
 
@MikeSpivey I am not reprimanding, nor do I say that you shouldn't be irritated at all. Mike Hardy is too close to my reputation not to be knocked down a peg ;-)
 
Goodnight and whatnot.
 
@AsafKaragila Yeah, a lot of whatnot :-) Is that what_0?
 
11:33 PM
'night, @Asaf.
 
?!, Asaf.
 
Goodnight, yadda, yadda... ;)
 
Good night, Asaf.
 
Hey @JM!
 
On that note, I'm glad Mike posted that question. Now I know what that is...
Hey rob!
 
11:37 PM
@JM: Thanks for your comment. Your answer definitely satisfied the question.
 
@robjohn no worries.
 
@JM Thanks for that. Hopefully the question won't get migrated. Simpson's paradox is interesting mathematically, and maybe others here will learn something simply by reading the question.
 
@JM: just getting up? It is supposed to be raining Sunday morning here. I don't think it has started yet.
 
@robjohn Nah, I'm just done with breakfast. I was up and running a few hours ago.
 
@JM Since you were out running, I tend to assume it is not raining heavily there.
 
11:43 PM
A few clouds. It hasn't rained in a week...
 
It seems to rain here on the weekends. It rained here last Saturday, and it is supposed to rain here tomorrow (Sunday).
 
11:56 PM
@JM Murphy's law as applied to non-mathematical induction: If you generalize anything from a small set of examples, the first case you haven't checked before publishing your conjecture will turn out to be a counterexample.
2
 
IIRC that was brought up in MO... :D
 
How can this have been asked for 3 hours and still nobody has found something for it to be a duplicate of? math.stackexchange.com/questions/83732
 

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