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3:00 PM
@Daniil Don't bother trying to figure it out, you'll go bonkers.
 
@AsafKaragila Oh ... now your an English Pofessor
3
 
facepalm
 
lol
So, are there any proofs that ZFC is consistent?
 
Yeah.
 
And if we prove that ZFC is consistent within X, can we prove that X is consistent within ZFC?
 
3:02 PM
From the theory "ZFC+Inaccessible cardinal" we can prove the consistency of ZFC.
 
And would that make any sense?
So you need a weaker theory to prove the consistency of the "subtheory"?
 
Stronger theory.
 
@AsafKaragila Oh English Professor can you show me -3 apples?
 
You can prove ZFC is consistent in the theory {1+3=4 and ZFC is consistent}
 
Hm, that's interesting.
@Holowitz can you point me to the proof, please?
Sorry, I am a newbie.
 
3:06 PM
My big understand about ZFC and large cardinals was a year ago.
I was talking to someone about how it baffles me how the theory ZFC+Inaccessible proves ZFC, and whatnot.
Then he said "Well yeah, you just use a stronger theory."
 
what is inaccessible cardinal ?
 
It is a regular limit cardinal which is also strong limit cardinal.
 
idgi
 
how does it prove zfc is consistent, iduction ?
 
No.
If you take kappa to be an inaccessible cardinal, then V_\kappa, which is the \kappa-th stage of the von Neumann hierarchy is a model of ZFC.
The regularity gives replacement, the limit gives union and the strong limit gives power set.
The rest is really automatic.
So V_\kappa is a set model of ZFC, therefore ZFC is consistent.
 
3:10 PM
ok, how many books does one have to read to understand it ?
 
Not many.
Depending on the previous knowledge, though.
If you're an engineer then you'd have to read more than a model theorist would.
 
von Neumann once said "young man in mathematics you don't understand anything, you just get used to it" What did he mean?
 
He was talking to someone like you, and he tried to shut them up.
2
 
do you know this for a fact Professor?
 
Yes, I was there.
 
3:13 PM
Do you know who he was talking to?
 
Someone who was 17 and annoying.
 
@AsafKaragila What would be a good start if I am familiar with basic mathematical logic, set theory, algebra?
 
Then I guess you were there
 
@Daniil How much set theory?
 
"is dense in the Banach!"
 
3:18 PM
Well, I know about ZFC, know how to construct set, Russell paradox, first-order logic, what is a formal proof, some order theory.
 
@Daniil I'd think that Jech's big book can be a fine start for modern set theory. The first part covers a lot of the basis and in quite some details.
 
@AsafKaragila Jech? Do you want him to stab himself in the guts?
 
@JonasTeuwen You really need to start compiling these... :D
 
I'd say that a set theory grad student should know pretty much all the first part of Jech, and at least half the second part. The third part is the advanced stuff.
 
3:20 PM
@JM The remarks? :D Yeah, they write quite odd things.
 
Yes, that one, @Daniil.
You can find it in your local library, and probably online in .pdf form if you don't mind those.
 
I don't want to be a set theory researcher, frankly. I would like to know set theory to the point where I can understand the questions & answers like the one you gave me.
So, maybe it's overkill?
 
Which answer?
 
If you're a beginner that book will drive you to suicide!
 
3:22 PM
If you want a survey, I'm not sure which one is good. If you want a book then Jech is a very good book. The first part is about 200 pages, that's not THAT much.
 
I want a quick fix to all the deep stuff of set theory too, I dont study math. I am reading Cohen's but its getting heavy pretty fast
 
Wait, you're reading Cohen's book about forcing without knowing set theory?
 
Yes, well I know the basics
 
Again, what basics?
 
Well a subset of what you can get out of wikipedia
and this site
 
3:25 PM
Nice.
 
I don't think that it's enough to understand forcing arguments clearly.
 
How do you do curly P for power set in latex?
 
@Matt \mathcal{P}
 
but its not about forcing only, it was meant as a self-contained and contains an introduction
 
I may not be a set theorist, but "subset of what you can get out of wikipedia" is sorta kinda vague.
 
3:26 PM
self-contained course
 
@Daniil Ta! : )
 
@Matt :D
I love abusing \mathcal
all the letters look so pretty.
 
Now that that guy is out: @Asaf, I presume you know that the chat has this excellent "ignore" feature...
 
Of course I know. I just prefer not to use it ;-)
 
Okay, then that's a different can of worms. :)
 
3:38 PM
@Asaf: I just posted some entertainment for you: math.stackexchange.com/questions/87417/…
 
\Omega being Ord?
 
Yes.
 
Sheesh, ads for Facebook and Google+? I'd rather they used the ad space to mention any new cra- er, features they might be putting into the SE engine...
 
I'm headed towards 3k rep : )
 
Community just bumped it up for being unanswered.
Hi all...
 
3:48 PM
Hi Srivatsan : )
 
Hi Sri.
 
Awesome. tb's back!
Wait, I don't get it. Has he been on the main site all the while?
 
4:08 PM
Yep, few hours ago.
 
Sorry, JM. I am too confused and distracted.
 
Been there. :) I understand.
 
hello there
 
Btw, I just noticed that someone upvoted that answer... =) Thanks!
I shouldn't have brought it up, I guess ;)
@JM What should I do if I find two accounts of the same person -- both unregistered?
 
I'd nudge the user to register, so that he can easily keep track of his questions, and won't lose the ability to comment on them.
Otherwise, flag the question associated with the later account, and ask that the account be merged with the earlier one.
 
4:17 PM
@JM Even if they are both unregistered?
You said something about no point flagging for unreg. accounts?
@JM Btw, the user's most likely a she. Anyway why would s/he lose the ability to comment?
 
Okay, "she". :) Well, if she's now using the latter account, she won't be able to comment on posts (questions and answers) associated with the former account.
 
@Srivatsan Huh? Not in this room anyway.
 
@Srivatsan Hence the nudge first. For the time being, I wouldn't flag if I were you.
@Matt He's been editing stuff on main a few hours ago, in response to Willie's plea on meta.
 
@Matt Does it really matter? It's now a matter of time, no?
 
@JM Yes, I just saw.
 
4:22 PM
@JM - what plea? One second...
 
Yay! : )
 
Oh yes, that one. I saw it just now.
 
@Srivatsan : )
 
@Matt, I didn't think you didn't know that he was on the main site. // I thought someone might have made that observation in chat earlier.
 
Why?
I missed it.
 
4:29 PM
 
hey guys
 
@JM Both of your removed that tag. So in effect, Noah did not do any edit on top of yours =)
 
I know; I just found it funny. :)
 
@AsafKaragila: What's "actual content" in your comment?
 
hi @JM
 
4:35 PM
Hi.
 
did you see my yesterday's question ?
 
@Matt Something which is not 0 or {0}
 
@RajeshD What I wanted to say was already said.
 
ok
 
@t.b. Are you in chat? I can't tell from my mobile device...
 
4:39 PM
No, @TheChaz, he's not yet in chat.
 
He is not here
 
Wonder how many people are going to come to chat tonight just to meet tb. =)
4
 
Ok thanks. I was going to ask if he would email me. Will check back later!
 
@TheChaz Ok, you're in luck. He just arrived.
 
Speak of the guy...
 
4:40 PM
@tb: Yay! You're back! : )
 
The prodigal Swiss returns! Welcome back @tb
7
 
How's Austria?
 
This room is somewhat incomplete without you : )
 
Hi all! Thanks for the warm welcome!
 
Good to see you back, @tb.
 
4:42 PM
@TheChaz I'm here. What's up?
 
Do you still have my email address?
 
Yes, twice.
 
@TheChaz Yes, I do. I'll write to you shortly.
 
Thank you! I have to sign off. The mobile chat experience is taxing :)
 
@JM Austria was great, a bit too cold for my taste, but the weather was nice enough for some walks at the Danube canal. Way too many tourists, though :)
 
4:46 PM
@tb It's not the first time you've been to Austria, is it?
 
@Srivatsan No it wasn't. I don't know how many times I was there (in Vienna most of the time). About a dozen times, I'd guess. Some very good friends of mine live there.
 
QED
hello
 
@tb : Hello Boss
 
Hi, Rajesh
@Srivatsan I just saw your comment. Note that this doesn't help because the OP can't flag herself (you need 15 rep for that) and given the questions asked so far, it is unlikely that she will earn that anytime soon. In such obvious cases I usually flag for the mods to merge the old account into the new one.
 
5:13 PM
@AsafKaragila: Will you say anything more about my last question? Or maybe write an answer that I can accept?
 
Yeah. I am not good with transfinite recursion theorem uses :-)
 
Ok, then I guess I'll have to wait for someone else to answer it. : )
 
@Matt I would correct the mistake too.
 
Am I right there, or I did something wrong?
 
5:21 PM
@AsafKaragila Why mistake? \mathcal(P)( \emptyset ) = \{ \emptyset \} but I don't have to spell it out.
 
The first line of (ii)
 
Blah, hard to keep track of the Matts. Now if one of them could use, say, "Matthias"...
 
@Gigili You are right, the answer in the OP is wrong (the first equality is wrong).
 
Where did we land on the ∞ = ∞ issue?
 
@WillihamTotland An abrupt end. :)
 
5:22 PM
*ignored*
 
@tb Thank you.
 
It says that P(0x|P) = P(0) = {0}, not P(|P).
 
Oh. : )
 
@Gigili By the way, wolframalpha is quite good at this :)
 
@WillihamTotland Kind of hard to deal with this, you see...
 
5:25 PM
@Gigili Your answer and the answer which OP copied from his book differ only in constant. Constant are unimporant in undefinite integrals. So both answers are in fact correct. (Both are primitive functions.)
That's what tards is explaining in the comment bellow yours.
 
@JM: I am shocked! Are you inferring that Skullpatrol is an idiot, or worse, a Skulpa-troll?
 
Thanks @Martin: I overlooked that in the OP there was a correct solution.
 
I did not say he was an idiot. He is, however, impervious to persuasion. Whether willfully or otherwise, I can't tell.
 
It feels that Skullpatrol and iyengar are blood related.
With the 'Sir' and the 'Professor' and the absurd writing.
 
@JM: Ooooh, I'm sorry.
The correct answer is "For one, the word is 'imply', and no; I'm stating it outright."
Thanks for playing, better luck next time.
But just to be clear on the issue; ∞ ≠ ∞, right?
 
5:29 PM
It's hard to read people like him. Thus, I did not wish to use the word "idiot" which is a bit harsh for this situation.
 
(Except for some narrowly defined cases in set theory, as I understand it)
 
@AsafKaragila: But it doesn't actually make any difference for how I defined F. Nice : )
 
@MartinSleziak Aha, I was trying to understand that comment but the constant 'C' we normally add after the anti-derivation process is something else, substituting x for 1+t^2 or t^2 would make the answer wrong, no?
 
@Matt Missed one... :-)
 
Okay, I'm confused when wolfram says the same thing @tb
 
5:31 PM
@WillihamTotland To be above board: you won't see me mince words. I'll say someone is an idiot when I have incontrovertible evidence.
 
@AsafKaragila Clear your browser's cache.
 
@AsafKaragila I disagree. They're barking up trees in different forests. One is in the department called "we left that way behind us" and the other one is called "there's still a long way before we can even dream of tackling that one".
 
@JM: I do not doubt this. I was merely trying to set you up for epic victory. :)
 
@Matt Ah, very good.
 
@Gigili I think that the example and the picture at this wikipedia article explain it nicely: en.wikipedia.org/wiki/Antiderivative
 
5:33 PM
Aha, got it got it ... they replaced C+1 with another constant C' .. Problem solved @MartinSleziak and @tb
 
@tb Perhaps.
 
@tb Flagged. Thanks.
 
It's amazing how many problems are based on the same idea as this one. I'd hesitate to say that they are the same problem, but perhaps some are.
 
@robjohn I didn't understand your solution, @robjohn. Give me a second.
 
@Srivatsan I was entering it on my iPhone while in the waiting room at the dentist. I might be able to expand on my answer a bit now.
 
5:48 PM
No no, it might be good. I overthought it, perhaps
From the expected number of white balls, how did you go to prob. of picking a white ball in the nth try?
 
I've seen this sort of problem so many times, I might be glossing some things over as obvious that really aren't.
 
That's a very nice way to look at the problem btw.
 
@Srivatsan Since the probability of drawing a white ball is the number of white balls over the total number of balls, and the probability of drawing a white ball is the expected probability over all cases, the probability of drawing a white ball is the expected number of white balls over the total number of balls.
Does that make sense, or should I expand on that some?
 
@robjohn Aw, right.
Now sure, I am a bit slow right now, so it might just be me...
 
Nah... I should probably add some of this in there.
I was being terse since I was entering things using the mobile interface (ick)
 
5:54 PM
Okay, I can't stay awake anymore. See you guys later.
 
Later, JM.
 
Good night, JM.
 
@Srivatsan I have expanded a bit, but I don't want to obfuscate too much with too much explanation.
@JM g'night
 
@robjohn Cool, thanks.
It's a very nice idea (+1).
 
when the answer is as simple as the OP was claiming, there is usually some simple explanation.
Of course, the exponent has to be n-1 and not n+1 as the OP claimed.
 
6:06 PM
@robjohn I was an idiot. I couldn't think of an explanation at the first glance, so I was doubting the OP's claim. =)
 
The first draw, the probability has to be 1 that a white ball is drawn
 
QED
> Also, many users find questions posted in the imperative ("Show that", "Prove", "Do", "Find") unpleasant and somewhat rude
I find this comment annoying
 
@QED meta-annoyance
 
@QED Well, what about it?
 
heh
 
QED
6:07 PM
only because it's been posted so many times
 
@Srivatsan it's amusing annoyance
 
Would you be kind enough, good sir, to show that...
 
@robjohn Many users find repeated posting of such boilerplate texts meta-annoying. QED.
=)
@Daniil - whose comment was that?
 
@Srivatsan I just made that up, frankly.
 
@Daniil G*d bless...
 
6:10 PM
@Daniil In this site, one could never tell... "Kind and Respected Pofessors. Bow to you all sir."
 
heh
 
6:22 PM
Can someone please give me an example of free category from algebra?
And it's underlying graph
 
QED
if the graph is a single point you can get free monoid
 
Well, yeah, I understand that, but are there any "useful" examples?
 
QED
:/
 
Uhm
Bad choice of wording there.
Well, for example, N is a free monoid and it's an understandable example of a known mathematical object viewed as a free monoid.
Is there something like that for free categories?
(Which are not free monoids)
 
@Srivatsan: I think R cup -oo , oo is the compactification of R. You don't need B-W to prove that it's compact. You'd construct a homeomorphism...
But then again, I don't really know what I'm talking about : )
 
@Matt Well, I am not quite comfortable with it. Infinity is defined in a particular way in that question... =)
 
@Matt: there is no such thing as "the" compactification, there are many, and this one happens to be homeomorphic to [0,1]. The result asked about in that question is equivalent to Bolzano-Weierstrass, as Srivatsan's answer shows. The other direction is even easier.
 
7:28 PM
Thanks for your link unrot work, @tb.
Can you estimate how many posts had such springer links?
 
@tb Yes. And I should read the links people post properly before I comment on anything.
Sorry, Srivatsan.
 
@Srivatsan No. I think I went through all the questions and answers that Google yielded on site:math.stackexchange.com eom.springer -"link rot". Unfortunately, most of those roughly 50 results are in comments.
 
No problem, Matt.
@tb Oh ok. So all the links are handled?
 
@Srivatsan I think so, yes, but it can't hurt to double-check :)
 
ok =)
 
7:35 PM
@Srivatsan: By the way: nice work on this one, although I needed to downvote the lazy question.
 
Thanks.
My first "answer" (that I edited before even posting) did all the bounding part by hand. Then it struck me that some of what I was doing must be known before.
It did not mention any of the words max-norm, operator norm, Weyl's inequality (perturbation). =)
@tb Ya, why not leave a comment though? =)
 
Because I commented on about 5 previous questions and the only result is that the word "please" was added.
 
Oh, =)
@tb That question is almost a Nice Question now...
I did a quick check. Most of the hits turned out to be the "Visit Meta" ads on the main site. =)
 
Yes, it looks ugly. I missed how it looked like before the edit; so I am not sure how much the "uglification" contributed to the ugliness =).
 
@Srivatsan This is nice: A new question tagged both algebra and number: math.stackexchange.com/questions/87461/…
2
 
@tb Done, thanks!
@MartinSleziak and nothing else. Exciting times.
 
@Srivatsan actually it was like this in the OP already, so maybe better change it back... Sorry about that.
 
I've retagged it, but feel free to give it more suitable tags, if you have som idea.
 
8:12 PM
@tb: I was looking for some paper from the 70's a few days ago and couldn't find it. Today I stayed at home, and I pulled a Buehler and found a .pdf scan :-)
 
@tb enoD. =)
 
@AsafKaragila :) So, you're learning...
 
Some could say that.
Tell me when you feel like translating another German paper ;-)
 
what is it?
 
@tb Just for fun, why don't you find a Hebrew paper to get translated? =)
 
8:16 PM
I need to find out why they only defined the property for natural numbers.
 
What do you mean by only for natural numbers?
 
matwbn.icm.edu.pl/ksiazki/fm/fm80/fm80112.pdf - last line of page 1 and first line of page 2
I need to understand what is a Kinna-Wagner principle, in essence.
@Srivatsan If it makes you feel better I'm helping my girlfriend in translating words properly from English to Hebrew.
 
@AsafKaragila Aw, I feel better, thanks. =)
 
Is today one of your days?
 
@AsafKaragila 'Twas, till now. I am pretty sure you can prove me wrong though. =)
 
8:30 PM
@Asaf: Did you try this, page 122ff?
 
Hm.. limited access through my paywall. Let me try some dirty trick.
@Srivatsan You think too much of me... or too little, depending on how you want to look at this ;-)
 
Too much. In fact, I am giving you credit... =)
 
Srivatsan! Hi :D
 
Hi, Clash. Are you surprised to see me? =)
 
Remember when I asked about if there is a sequence a_n with lim n->infinity=0 and \sum (-1)^n*a_n diverges
and then you suggested me to try (-1)^n, and then it helped me understand that (-1)^n/n should work
 
8:35 PM
Yes, I do remember, Clash.
 
I just read the question again and it says "a positive sequence a_n", does this mean it can't alternate? Would (-1)^n/n be invalid?
I'm just so happy to see you here :D
 
@Clash May be we can take it to some other room?
 
sure, how do we do that?
 
@Asaf are you still here?
 
@tb: Yes I just got to the .pdf file
What do you mean 122f?
 
8:37 PM
Page 122 and the following ones.
 
By the way, I saw a similar file in treeware on my advisor's desk the other day. It was pretty neat. Typed out in a typewriter and the mathy stuff was filled by hand.
 
Yes, the famous filling in process. Halmos describes that somewhere. He dictated the typewriter stuff to his secretary and said what kind of symbols he would need to fill in later...
 
Drats. The principle only speaks about P(alpha)... Monro actually defines the generalization.
Any chance of figuring out where, if at all, Monro is working?
He is probably emeritus by now.
Well, I'm gonna get going for a while. I shall return at a later hour.
 
@Asaf: here :)
 
@Srivatsan If you have to ask, you'll never know.If you know, you need only ask.
(whatever that means)
 
That doesn't make sense. Shouldn't it be "... you need not ask." at the end?
 
Even if none of the answers seem to say anything meaningful, it's quite hilarious.
"Are you dating a philosophy major?" =)
 
Oh! Actually yes. The first answer sheds some light on it...
 
u meen de 1st answr ?
 
8:58 PM
@Srivatsan Or "Are you trying to propose to someone?" : ) => proposal fail : )
 
@Matt Aw, it does make some sense. Thanks.
 
@tb U haz teh lolz?
@Srivatsan No, thanks yourself : )
 
Ok, thanks, Sri.
 
@Matt ack. ima tryna wr8 w/ boxng gluvz
 
: D
I thought you didn't do internet memes. Maybe just not rage comics...
 
9:04 PM
I just gave it a try whether it is faster than actually typing the words in full. It isn't.
 
@tb and @Matt, is there a standard example of a sequence a_n such that: (a) a_n > 0, (b) a_n converges to 0, (c) \sum (-1)^n a_n does not converge. [To prove "tightness" of Leibniz test.]
I know it won't be nice simply because it is not monotone decreasing.
 
I'll leave that to t.b., I should really get one more homework question done...
 
Ok, @Matt.
Clash solved his own question. Thanks, @tb.
 
@tb Honest to god, I thought you're pulling one on me!
It makes sense, though. He retired from mathematics in 2006...
 
@AsafKaragila First I found this. Then I looked further and I'm pretty sure it's the same guy.
:)
 
9:15 PM
:-)
 
Actually publication 46 is the one you linked me to.
 
Interestingly enough he says nothing about his math life on that site.
Well then, I will have to send him an email about a couple of things later tonight. But now, beer time.
Ciao.
 
So you're not into Dry choices tonight?
Ciao
@Srivatsan: If you continue like this, you'll be capped at 9995 :)
 
@tb Well, =)
 
9:35 PM
I can always edit a couple of tag wiki summaries. =)
 
Or just wait a few more hours...
 
9:46 PM
@Srivatsan Maybe 1 wiki summary + 1 wiki excerpt - 9999 would be nice number.
 
@MartinSleziak =) That's only if I cap out today.
 
But you can get over 200 if someone accepts at least 1 of your answers.
 
Xmas shopping with my wife. Just checking in...
 
I can ask my own question and answer and accept it. I will get +15+2 from that. =)
 
@Martin you don't count accepts for capping
 
9:51 PM
Yes. That's why Srivatsan can get more than 200 rep for today and get 10k today already.
 
I was on the cusp like that for several days. I hope Srivatsan doesn't have to do that.
It is not easy finding info on the mobile interface :-(
 
It seems someone upvoted my question now =)
 
I won't be back home until tomorrow server time.
@Srivatsan Besides, I usually don't understand the topics that you answer
 
@robjohn Really? I answer only "easy" questions, no?
 
Can you put a link here so I can actually get to one?
On the mobile, Ivan get your chat profile only
I can, not ivan
 

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