whoah, Qiaochu is over @ theoreticalphysics.se!

Has ANYBODY here read "From Zero to Infinity" ???

or even heard about it

Qiaochu makes me feel like there's no ppoint doing anything

same as Terry Tao

@Skull: I probably skimmed it at the library in high school or something like that. I've heard of it.

I need little help devising the formula for this -> If a man travels distance x at a kmph and same distance at b kmph , then what is the average speed?

average speed is what exactly

HINT: average speed = total distance / total time. Total distance is obvious: it's 2x. What's the total time taken?

Srivatsans way is nicer

@Srivatsan Time isn't provided

calculate it

@FreakEnum Can you calculate the time taken for each of the two segments of the journey?

@Srivatsan gimme min, I'm trying

(a+b)/2=the average speed

kmph

@Skullpatrol wrong

2x / (a+b)?

it's averaged over time not distance

no

It wasn't me

@Skullpatrol That is wrong answer

@Srivatsan I am unable to derive time taken

rate = distance / time

so if distance = x and you have the rate, derive time

Can you guyz hold on your answers for some time?

@anon It's usually called "speed" in this context. =)

hold down?

@Srivatsan speeds are different we know , how do i derive total time taken for that, which are dependent on speed?

"a" is not the speed ?

@FreakEnum use distance = speed * time

@QED ok you tell me the answer!

what

@QED average speed!

@FreakEnum Ok, the journey is broken down into 2 leg: from A to B, and from B to C. Each leg is distance x, so total distance 2x. Now, it's given that the speed in the first leg is a; the distance is x. So how much time would the first leg take? // Do the same thing with the second leg of the journey. What's the total time (= sum of the time required for leg1 and leg2)?

@Srivatsan x/a

( a[km/h] +b[km/hr] ) / 2 = average speed[km/hr] for example 100km/hr and 50km/hr would give an average of 75km/hr

lol

= 150/2

@FreakEnum Go on. You're in the right direction, but you should complete it.

@Srivatsan total time is x(a+b)/ab

waitaminute, are you allowed to put Dirac deltas into asymptotic equations or is that just physicist voodoo? :)

@FreakEnum Now, what's TD/TT?

@Srivatsan cool , answer is 2ab/(a+b)

@FreakEnum That's correct.

@Srivatsan Thanks a lot:)

You're welcome, FreakEnum.

@anon - which page, anon?

the very first two equations

@FreakEnum See also the Wikipedia page on the harmonic mean (in physics).

@tb No, but Halmos was probably a way better writer than I am now :-).

The postdoc in my office has a typo in the very first equation in his thesis :-).

Can you guyz prefer me easy to read maths bible? :)

@tb Thanks for link :)

@JonasTeuwen better a typo in the first equation than in the title... (see the foreword) :)

@tb I have the book by Laurent Schwarz... "Théorie des distiributions".

@FreakEnum How about the Princeton Compagnion to Mathematics?

I don't think that is what Freak needs

@QED Then what I need?

Well. In that case: There is no such thing as a maths bible.

@JonasTeuwen So two typos, one in the name and one in the title?

This is the longest answer I've seen.

@tb Oh, excuse me, the first typo is mine :-).

Schwartz*.

@JonasTeuwen and Companion

@JonasTeuwen 0_o That book is awesome expensive :D

@Jonas Did anyone tell RajeshD that phyra is a girl?

@Ilya I'm not sure. Why?

@Ilya Yes I was there when they did.

@Matt I'll blaim my keyboard.

@JonasTeuwen he seem to look for them

@Matt the search is on...

: )

@robjohn )) nope, stop it, please

@Matt This is a way to find the longest answers

@Ilya but I know I've posted a longer proof...

@robjohn mine was also long until you fixed it

@Ilya Does he harass her then?

@Ilya which one did I fix?

@robjohn with recursive investments

@JonasTeuwen dunno. Just curiosity. I've found an easy way to generate gravatars

@tb My eyes start to hurt : D (I like your comment)

Those long answers are like Heap Overflow errors :D

@Ilya Ah, that one. The right auxiliary function popped into my head on that one.

That doesn't seem relevant

@Matt thanks for making my browser barf...

@JonasTeuwen: Have you read the Companion?

@robjohn My pleasure. : )

@Matt Not completely.

"lol, btw. I think there is a mistake in line 0′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′ ;)" Really!? =)

Is this question a dup? See also the link in my comment.

@Srivatsan 6 Bangles each of 4cm in daimeter,what is ther minimum diameter of plate required so that each bangles are kept without overlapping(bangles touching each other) -> now how to start with this question?

@JonasTeuwen What do you think of it?

Not sure. One can get obvious lower bounds, but I doubt that the correct answer is that obvious.

@tb: Do you know much about non-abelian homology then?

@JonasTeuwen I don't agree with your comment " There is no such thing as a maths bible" with all due respect

Fine. You give an example then.

@Matt It is ... a nice curiosity. I'd like to have it.

Euclids Elements

To read a bit about fields I'm totally ignorant about.

I agree with Jonas and will go one step further: there isn't and will never be a maths bible on Earth.

@Skullpatrol Does that contain modern algebra? No. Does that contain modern analysis? No.

Maybe you can have an "elementary analysis bible" :-).

@ZhenLin No, not really. I glanced at the paper and decided that I'm scared by words like weakly pointed protomodular left semi-abelian categories.

I agree with Elements being a math Bible. It's two millenia old, probably outdated, I don't really wanna read it...

@tb :D.

@JonasTeuwen It has been said that it is the next most read book to the actual Bible

I didn't read any of those two.

@Srivatsan the statement is not true for spherical or hyperbolic geometry.

I've read parts of the Bible but not the Elements.

@robjohn: I think your avatar is intimidating. Is that on purpose? You look angry whenever I look at you.

I've read the part with the monsters and such. Mildly entertaining :-).

@robjohn So, for the case when it is true, is it a dup? =)

That means that something has to be brought into play regarding the parallel postulate or something...

@tb My lecturer is one of his collaborators. The world of category theory seems to be very small...

@Srivatsan Oh, about being a dup, yeah, it looks like it.

@Matt, he's a mean square :)

Sorry I got taken in by the problem itself

@Matt look at my profile... :-)

I know the pun but I was wondering if the side effect was intended. Not that it matters so much anymore, now I know that you're quite alright.

@Matt mean square -- intended, no?

@Matt Well, we were talking about proof by intimidation the other day...

@ZhenLin Didn't you say that your lecturer was in Louvain at some point? Then it's not that surprising.

Proof by intimidation is how Euclid does it in the Elements & how the Bible does it to

@Matt This was the start chat.stackexchange.com/transcript/message/2529530#2529530

@tb: Nah, they met at PSSL 83, I think.

@robjohn This is nice: Asaf would love it see that comic pop up once again in chat. =)

@Srivatsan I pointed him at it once before.

@robjohn Yes, I might remember that.

Can you create numbered equations in a question, using \begin{equation} and \end{equation}, and then refer to them by using the \label{} and \ref{} commands? I've tried using these but nothing shows up in the preview. Do I have to post it for it to work, or isn't it supported?

@Speldosa: I suspect it isn't supported.

@ZhenLin :'(

@ZhenLin Ah, I see. That was another lecturer then.

@Speldosa You can insert tags at least (manually, though).

@Speldosa: Are you talking about on MSE? You can use \tag{} (but it's manual as tb says)

Using \tag{} in each line you want to refer to.

And \ref{}?

@tb: No, same person. She was working with him while a student.

@robjohn thanks!

@robjohn What is more intimidating than being told that a "point" is that which has no size... as an axiom

Dunno about \ref. Why not just $(2),(3)$ it or whatever?

\begin{equation} is supposedly better to use than $$ but I think they are the same in MathJax.

@anon I'm damaged from using LaTeX to much.

I usually just refer with $(1)$

math.harvard.edu/texman/node18.html#SECTION00081000000000000000

@robjohn: The equation environment includes automatic numbering, but $$ is more like the equation* environment.

This document is what's references to in the right sidebar.

*referenced

@Speldosa Yes, but that doesn't work in MathJax. You probably need more document structure that doesn't exist in MathJax to port the numbering from LaTeX

@ZhenLin but not in MathJax, I believe.

@Speldosa \label is simply ignored in MathJax and \ref and \eqref are nonexistent.

MathJax is for short blurbs, LaTeX was intended for papers and books.

@tb Great. Then I know.

:) you can edit previous comments by hitting the up arrow key

(during two minutes)

Oh yeah. Forgot about that.

@tb up arrow, or clicking to the left of the comment to be edited (and clicking 'edit').

@tb: How to retag this post? math.stackexchange.com/questions/21992

@Srivatsan Not at all.

Is "no tag" allowed? popular math?

Don't bump rubbish, please.

Er, sorry.

Is there some decision to get rid of the (number) tag?

In that case, I added a vote to delete it. If others could pitch in.

There's some agreement, yes. Not sure if it came up in meta.

@Srivatsan it seems to be gone. does lhf lose 20 rep then?

@robjohn Oh, no idea. :-/ I didn't think of that.

@robjohn s/he will.

But are "The number 1. At least if you agree with Kronecker." + link really worth 40 rep?

That's too bad... :-(

I don't know, but it will come as a shock.

@tb This post proposes getting rid of (number) tag: meta.math.stackexchange.com/a/2755/13425

I can't see how many have voted to delete.... is that above my pay grade?

wait, I did see it before, but now that I've voted, I can't see it any more.

@robjohn if you go there and reload again, you can see it. At least I can.

Anyway, the three of us talking in the last few moments are responsible.

The deletion notice is under the closed banner.

Only 3 votes for deletion?

Yes.

@tb Well, that's why I don't see a count.

and since I refreshed I see that it was indeed deleted.

And you see who deleted under the list of persons who closed the question.

Damn! I broke a wine glass.

What a waste of perfectly good wine.

I wonder how the four color theorem proof is?

> It has been known since 1913 that every minimal counterexample to the Four Color Theorem is an internally 6-connected triangulation. In the second part of the proof we prove that at least one of our 633 configurations appears in every internally 6-connected planar triangulation

Good night!

hi

So separable Banach spaces can become inseparable when you take tensor products of those?

@Potato, did your gravatar change?

I believe so. Not sure why.

In case you had not entered an email address, your gravatar would be based on your IP address. so it would change if your IP changes.

Ok all, I need to go now. Bye!

Ciao.

I don't know whether Patrick Da Silva or I have the right amount of detail for this question, but one should be right for the OP, I would think.

@JonasTeuwen What do you mean?

Well, someone told me that the tensor products of separable spaces does not have to be separable!

Then I suppose it must be infinite products right?

@JonasTeuwen I would think so.

Sometimes the way we define the topology of infinite products is nice for some properties and not for others. It's nice for compactness, but evidently not for separability.

@JonasTeuwen Yes. The finite linear combinations of elementary tensors of dense subsets will be dense in the algebraic tensor product which in turn will be dense in any (reasonable) tensor product (i.e. one satisfying \|u (x) v\| \leq \|u\| \|v\| for simple tensors).

That sucks :-).

Our next seminar is about tensor products of vector spaces!

Ryan's book, I suppose.

gotta go for a bit. be back tomorrow (server time)

In two weeks I need to talk about Choquet theory.

@tb Yes.

@robjohn Well, it shows the correct current time for me!

@JonasTeuwen Oh, I thought it was sooner than that

So I'm not sure what "server time" is.

@robjohn Bye :-). (No, I still need to read the book)

See you, robjohn

@JonasTeuwen server time is Universal Time, and that is when rep and capping and things occur.

Okay :-).

@tb I'll only be an hour or so.

@tb Damn! 79,95€!

Isn't it available electronically?

I mean on Springer Link?

Not on springerlink.

Hm. I found it for about 30 Euro somewhere. I'm not a big fan, but there's nothing better on that basic level.

Let's check bookfinder.com !

Cheapest 70€ :-(.

Why are some Springer books so expensive and some quite inexpensive?

I don't know. The most expensive one I have is Margulis's thesis which is about 4 Euro per page...

Another maximiser is Serre's complex semisimple Lie algebras

4€ per page? :-)).

Well, maybe leaf: Roughly 250 bucks and 130 pages.

Holy cow!

And then there's Wiley's hilarious pixely photograph-PODs like Kobayashi-Nomizu or the like. Ridiculously priced.

Elsevier's Sobolev Spaces? :-). 140€ iirc.

Well, buy a comptes rendus article. $40 for 4 pages :)