The h Bar

3:36 AM

[Division by zero] The findings are now summarised in my wiki page

MAFIA, if you don't mind, could you have a look at it and see if it makes sense to you?

user116211

4:08 AM

@Secret It's looking good at the first sight; but I will read between the lines in off-time.

user218912

I was working through this question then I lost my thought process and forgot why I did something earlier even though it's right...

user218912

idk why I did it but I need to do it again

user218912

me 5 minutes ago was smart.

@MarkMitchison What's the best book on stochastic processes? Don't think too hard... what's the off-the-cuff answer?

Will

Anyone have an idea how the energy required to compress a fluid compares to the energy theoretically obtainable by a turbine moving in the opposite direction?

user116211

4:16 AM

@Will flagged as engineering

user116211

Anyways, welcome @Will :)

user116211

@DanielSank o/

user116211

@bl00 :(

Will

hi @MAFIA36790

If we leave out the gritty parts there's still some physics there I believe...

user116211

No, no; just kidding; ask anything here.

user116211

4:19 AM

If someone is interested, he will respond.

user218912

@MAFIA36790 did you just assume the gender of people in the h bar?

user116211

No.

user218912

yes you did but w/e

user116211

._.

user228700

4:42 AM

Yeah, I think u just did ^ @MAFIA36790, even tho it's a pretty fair generalization 'cause, like, max. 2-3 females frequent this room.

user116211

No; it just came while I was writing the comment; I generally write he/she; but yeh just a generalisation.

user116211

Oct 13 at 14:19, by MAFIA36790

@AaronAbraham You don't have to ping anyone; just ask. If someone is interested, he/she will respond.

user116211

Noticed that?

user116211

I generally use he/she; but don't know this time what happened; just wrote that ;/

@MAFIA36790 \o

Hey @MAFIA36790, send me a link to some awesome Indian music!

You too, @Kaumudi.

user228700

4:51 AM

@DanielSank: What kind of music are we talking about?

I remember dancing with a bunch of physicists at a party at a conference once. There were several Indians there, and once the Indian music started, that's when the party really got going.

@Kaumudi Well, I'm working on my linear algebra book, something compatible with thinking and working.

user116211

@DanielSank, You like Pete Seeger?

^ Who's that?

user228700

Wtf, u're writing a book?! @DanielSank

@Kaumudi Started it as an undergrad.

user116211

4:52 AM

@DanielSank Did you read Hoffman Kunze?

user228700

Holy crap 😱

Yes. At some point I realized that I wasn't aught how linear algebra fits into physics properly (particularly w.r.t. the Fourier transform) so I wrote a book :D

It's not very long.

~40 pages.

It'll probably be more like 60 by the time I get all the figures in there and add a section on Green's functions.

user228700

Oh, wow.

user116211

Pete Seeger

Peter "Pete" Seeger (May 3, 1919 – January 27, 2014) was an American folk singer and social activist. A fixture on nationwide radio in the 1940s, he also had a string of hit records during the early 1950s as a member of the Weavers, most notably their recording of Lead Belly's "Goodnight, Irene", which topped the charts for 13 weeks in 1950. Members of the Weavers were blacklisted during the McCarthy Era. In the 1960s, he re-emerged on the public scene as a prominent singer of protest music in support of international disarmament, civil rights, counterculture and environmental causes. A prolific...

Here's the github repo with the LaTeX. It won't build right now because I'm changing the file structure around a bit.

user116211

4:54 AM

@DanielSank WoW!

Yeah, I decided I need to just get this thing done.

user116211

I've not read any maths book from physics point of view.

I can probably actually publish it when it's finished.

user228700

OK, @DanielSank: So we're talking about exclusively Hindi music?

user116211

@DanielSank Springer? or Wiley?

4:55 AM

I gave a two-part lesson series to my undergrad journal club on this topic, and it was very successful. One of the deans asked for the document so they could use it in classes!

@MAFIA36790 Probably an on-demand online publisher unless one of the real publishers is actually interested.

@Kaumudi Nah, whatever.

user116211

Tell me @DanielSank when you publish.

@MAFIA36790 Sure.

user116211

Phys.SE have some authors but most of them are mathematical based.

If I'm really dedicated I could probably finish the document in two months.

@MAFIA36790 ?

user228700

I can't work with that 'cause there is just so much. I don't even understand if u're looking to concentrate or to party (since u mentioned both)...

user116211

4:57 AM

@DanielSank Valter Moretti, Arnold Neumaier, for example.

@Kaumudi Concentrate. I only mentioned the party because it's a fun memory.

@MAFIA36790 Ah, well this is a math book too ;)

user116211

@DanielSank yes; but you said from physics point of view, isn't it?

user228700

OK. I don't think Ik any Hindi songs that allow me to concentrate more; almost all of them either make me emotional, or they have me jumping up and down.

user116211

That would indeed be a good step to write a book from physics' point of view; that would make the book different.

user228700

I recommend stuff like:

Jon Hopkins - Contact Note - Full album

5:00 AM

@MAFIA36790 Well... sort of! It's from the physics point of view in the sense that the math is motivated to the reader by dropping a problem in their lap that they probably can't solve.

user228700

Tycho - Dive {Full Album}

Then the book says "If you wanna solve this, read on!"

user116211

@DanielSank Good!!

user228700

user116211

@DanielSank Now, that's like a badass statement ;))

5:01 AM

Also, throughout, the book points out many places where the reader probably already learned the math in the book but didn't quite realize that it's all related.

@Kaumudi listening...

user116211

Morning @JohnRennie.

Maxence Cyrin - Where Is My Mind (1 Hour loop)

'morning, Sir @JohnRennie

^ Great minds...

user228700

Or even just:

user228700

user228700

(Although this ^ can become kind of annoying :-P)

user228700

5:03 AM

I have all of the above on my phone and I listen to them when I'm pissed with Math but have to do it anyway.

user228700

@JohnRennie: Morning! :-)

Morning, morning.

@JohnRennie You're a morning short. Better give us that third morning before the police notice.

user228700

@DanielSank: Tell me what u think.

user228700

I was trying to find one more...

5:10 AM

@Kaumudi Didn't like the first one.

user228700

Last year, I had this exam coming up and it was all derivations from optics and I knew nothing. So I had like 4 cups of coffee, blared that one video and then just kept studying till like 3:30 in the morning and by the end of it, I was super confident in all of the derivations. Plus, this stuff makes u feel less alone when u're pulling all nighters.

Tycho's nice so far.

user228700

@DanielSank OK...

@Kaumudi here's one for you.

user228700

5:17 AM

I'll check it out when I use the laptop next.

user228700

Thanks :-)

@Kaumudi Awwwww, rats.

user228700

Yeah :/ I'll check it out on my laptop later. Tell me if u liked "Dive" after u're done. Now I'm off to do more organic chemistry!

@Kaumudi I like tycho.

user228700

@DanielSank Cool :-)

user228700

5:28 AM

@JohnRennie: Are u familiar with stability of resonance structures in organic Chem.?

@Kaumudi well I know what resonance structures are ...

user228700

OK...

user228700

Can u help me to understand this:

user228700

I don't really get how structure (B) is more stable than structure (C)

user228700

5:31 AM

Oh, and these are those points:

user116211

+ is in C?

user228700

@MAFIA36790 In (B) and (C), yes.

I don't know I'm afraid. Organic chemistry was always the area I was least interested in, and I haven't studied any for the better part of forty years.

user228700

Oh, alright... :-( Now that Orthocresol is mod, Idk how much time h/she will have to clear my doubts...

5:35 AM

you want the +ve charge to be in a less electonegative atom. N don't like being +ve

user228700

Yeah, I got that, but what about (B) and (C) ?

How do you write, in math, "For all A and B in set S"?

as for the third one, there are not enough electron density to keep that C+ happy

@DanielSank $$\forall a,b \in S$$

user116211

$\forall ~a,b ~\in S\,. $

Oh ok. You just put a comma.

Thanks, guys.

user228700

5:37 AM

@Secret Hey, but there isn't a positive charge on N in (B) either.

think carbocation, (B) has two group stablising it with electron density

user228700

Ohh, riight.

user228700

Hey, whenever there is a positive/negative charge given on a structure, what does that indicate? FC of the atom in question? So it has how many more/less electrons?

Ok how do you say "For all blah blah, something is true"?

$$\forall a \in A, \text{statement}$$

^ That?

@Kaumudi roughly speaking, it is the no. of pairs of electrons lacking (- for extra) compared to the atom in its neutral state

user228700

5:43 AM

Pairs?

user228700

Are u positive? (No pun intended :-P)

yup. since each full arrow pushing is a pair of electrons

@DanielSank there are two ways, one of them is to use : to denote "such that", another is to use | instead of :

user228700

So those carbon atoms need two more electrons to become neural?

I don't want to say "such that" though.

Actually, perhaps I do...

user116211

@DanielSank $\forall a: A(a)$

5:46 AM

ok

statements like those tend to appear inside curly bracket, which then specify what elements are inside that set

@Kaumudi yup

user228700

:/ OK...

user228700

Hey, do u know what the term mesomeric energy means? (I'm so sorry, but I googled it and came up with nothing :/)

user116211

@Kaumudi mesomeric energy?

user228700

Yup, typo, sorry.

user116211

5:49 AM

It's resonance stabilisation energy.

Oh hey MAFIA

I wanted to thank you for your post in the Heisenberg uncertainty principle

user116211

Hello @IanEmnace; welcome to The h Bar.

I just didn't want to put it in the comments, cause the comment explicitly said "avoid comments like 'thanks'"

user116211

sure.

user228700

@MAFIA36790 OK, I'll google this...

user228700

5:50 AM

Dude, whenever u had questions, what did u do?

user228700

(Seeing as u studied by urself and all)

user116211

@Kaumudi yes and SE.

@Kaumudi umm, sorry mistake that carbon only need one more electron to become neutral. Didn't noticed one end of the bond is fixed, thus one of the electron was not moved. Similarly for the N

@IanEmnace Hi Ian. Shall I edit the second GIF into your answer?

user228700

'Cause the frequency with which my mind comes up with questions is bizzare and also, irritating to the people here...

5:52 AM

Ah yep, sure, I tried but I couldn't include it as an image.

user228700

But I can't move on until that question has been answered either :/

user228700

So what did u do? @MAFIA36790

@Kaumudi you didn't know me in reality, but I am literally famous in my uni because I ask so many questions

user116211

@Kaumudi Same!!

@IanEmnace Yes, I think the SE restricts the number of GIFs you can include when your rep is low. I'll do it now.

5:53 AM

Oh I see, alright, thanks.

user228700

@Secret Yeah, same here. My classmates and my teachers used to call me "Doubt Kaumudi", no kidding.

user116211

@Kaumudi I read books; if I didn't understand one, I would see other. Then I googled to see if there is any relevant content; if not then checked SE if there is some post related; if not, then asked in SE.

user116211

You should read this chapter on Feynman: feynmanlectures.caltech.edu/III_10.html#Ch10-S4

@MAFIA

user116211

The claculations are in the beginning of the chapter.

5:54 AM

@MAFIA36790 how long did it take you to get where you are now?

Sorry, I thought Enter auto-completed

@IanEmnace Done

I have many ways to handle that:
1. Read books
2. Ask professors after lecture
3. Discuss with friends and the smart guys
4. google
5. (Very useful for maths subjects) Experimenting by doodling with the algebra on pen and paper and try to see what happens if you change one paramter

user116211

@IanEmnace I'm simply nowhere; I'm a freshman.

Thanks @JohnRennie

Really? When I was a freshman I knew jack about quantum mechanics lol

Of course, because I knew SE existed, after my 3rd year, I have two more options:
6. SE
7. Chat

user228700

5:56 AM

@Secret: I can't do all those things :'-( I can read books, google, doodle, and ask people here, hoping and praying that I don't get banned for asking so many questions.

2,4,5 tend to be my most used methods. Most professors like ppl asking questions, but some cannot handle it

user228700

(I have a weird life; I don't see anybody outside of my family on a daily basis. I can't discuss with profs/friends 'cause I have neither)

user228700

So...yeah, SE is my only hope and I can't post very trivial questions as actual questions so again, I have to wait until someone answers here at the chat...

user228700

@MAFIA36790: Did u have friends to discuss with, in 11th and 12th?

user228700

Or any other resource..?

user228700

6:02 AM

?

user116211

@Kaumudi No.

user228700

So all ur doubts were cleared by googling/chat itself?

user116211

I have discovered chat recently; prior to that? yes, SE helped me a lot shunning away my confusions,

user228700

What about very trivial questions..?

user116211

Like?

user228700

6:07 AM

Well, maybe not trivial exactly, but what about specific questions?

user116211

like ;P

user228700

They'll get closed off as H.W on the main site.

user228700

Like that picture I posted before.

user116211

ohh.

user116211

i hardly asked HW questions here.

user228700

6:09 AM

It's not exactly H.W, u know...

@Kaumudi When (if) I get the new site going you'll be able to ask there :-)

user228700

How did u deal with those kind of questions is what I'm asking...

user228700

@JohnRennie New site?!

14 hours ago, by John Rennie

@DavidZ let me get this over with quickly because you'll all disagree ...

user116211

@Kaumudi I mostly tried to solve myself; I had some good tutors who helped me a lot.

user116211

6:12 AM

@JohnRennie Don't you think such proposals have been tried earlier and also been raised in Area 51?

user116211

Like Physics Underflow ?

user116211

Well, no one liked such proposals.

user116211

After all, SE is not for HWs.

user116211

However, if you have something different in mind, let me know.

Yes, similar things have been tried and failed but I think it's worth another go.

The idea is not to do peoples homework, but to provide the sort of help with problems that we supply here in the chat.

user116211

6:15 AM

It is noteworthy to mention that Math.SE is more tolerant to homework questions.

i.e. focus on the methods used to solve problems not just the answers

user116211

There are tons of answers that go like:

user116211

Hint: ....

Q: My question was closed on Phys.SE. Can you recommend me another internet site where my question might be on-topic?

If I decide to go ahead with this I'll start by posting a proposal in the Meta to explain exactly what I have in mind.

user116211

yeh, sure.

user228700

6:16 AM

@JohnRennie: I do think that this a good idea. For some of the same reasons as u...

user228700

Hang on, actually, there is an existing website for this same purpose of helping with homework questions; when people are stuck 'cause they haven't applied the correct concept/have misconceptions. I'm searching for it...

user116211

Just don't make it resemble it like a forum; you know SE is not a forum; chat is different thing @JohnRennie.

user116211

@Kaumudi Reddit?

user228700

@MAFIA36790 Very funny.

user228700

Aha! Found it:

user228700

6:21 AM

toughstem.com

user228700

@JohnRennie

user116211

19

My question was closed1 on Phys.SE. Can you recommend me another internet site where my question might be on-topic? Here we keep a list of other internet sites that might help students2 of physics. One site per answer. To keep the list at a reasonable size, please only include sites which fulfil...

@Kaumudi the advantage of the SE is that its rep and voting system make it clear who the trustworthy answerers are. On sites like the Physics Forum you never know if you can trust answers.

user228700

That's not Physics Forum...

user116211

@JohnRennie PhysForum is really messy.

user228700

6:22 AM

But no, that's not anything like what u're proposing either...

user116211

Pages after pages go with on and off comments.

user116211

Really hard to find the answer among the heaps.

@Kaumudi If I decide to go ahead (and there's a 50/50 chance I won't) then the site will be called Learning Physics or something like that. The emphasis will be on learning how to solve problems, not just on providing the answers.

user228700

@JohnRennie: It's very frustrating when I'm stuck on a problem but I can't ask here 'cause it'll get closed. 'Cause there is almost always some misconceptions associated with the inability to solve the problem. And unless u can ask someone about it, u won't learn.

user228700

And this is exactly what I've been doing by asking u...

6:26 AM

@Kaumudi that's exactly the sort of thing I have in mind.

user228700

Would u agree if someone were to accuse u of helping me solve all my homework questions?

user116211

I hereby ACCUSE JohnRennie for helping homework monsters!!

user228700

😑😑😑

user116211

There will be a trial now.

I don't think there's a problem in helping a student understand their homework. I do think there's a problem if you do their homework for them.

user228700

6:28 AM

Yeah, that ^

Anyway, I need to go offline for a few minutes as work (i.e. paying work) calls ...

user116211

@JohnRennie, I saw some meta posts where opinion like homework questions helped to clear concept and learn physics, surfaced.

user116211

Well, there is some reason why Bourbaki hardly contains any exercise.

user228700

@JohnRennie I'd pay you for all the explaining u do, no kidding. Although, since I'm almost broke, it wouldn't compare to what u get for all the computer stuff u do.

user116211

7:00 AM

> If there's one thing the USSR did right, it's STEM education.

user116211

;)

quantum-mechanics newtonian-mechanics

I think India does pretty well too. It's just in the so called advanced western economies that there's a critical shortage of people with even basic STEM qualifications.

user116211

The old Soviet Union books are quite famous here.

user228700

7:33 AM

@JohnRennie Oh, India is overdoing it, to say the least.

user116211

-3

Q: Timeflow Theory

John David Best has his web site Vida İnstitute. He put my articles page in 'Timeflow Theory' 'http://vidainstitute.org/?page_id=656'. Vida Institute is intersting site. And my web site is www.timeflow.org In your opinion, discovery of a planet is more exciting. Or, as I've presented in the atta...

user116211

KILL IT!

@Kaumudi I don't know enough about India's economy to comment, but I'd be surprised if a developing economy could have too many engineers. Your point may be that it's unfair to force students into becoming engineers if they don't want to, but that's a different point.

Mark Mitchison

8:22 AM

@DanielSank Gardiner's Handbook of Stochastic Methods

But van Kampen is also good. Gardiner takes more of a stochastic calculus approach, van Kampen is more focused on the master equation.

ManishEarth

@JohnRennie is right. India has a lot of folks who are engineers by title, but never wanted to be or aren't good at it

user228700

8:39 AM

@JohnRennie: I don't understand how it's a different point, since u said "India does pretty well too". I was merely pointing out what ManishEarth has said. More than half the engineers who graduate from the tens of thousands of engineering colleges in India remain jobless/are misemployed.

@MarkMitchison Ok, thanks. I have Van Kampen and have been slowly working through the exercises.

> More than half the engineers who graduate from the tens of thousands of engineering colleges in India remain jobless/are misemployed.

Ah, I didn't realise that.

user228700

Riight.

I'd like to see the split between unemployed and misemployed. It's very common to see technically trained people working outside their discipline but in fields where their training in analytical thinking helps.

user228700

@JohnRennie Eg: My father is the director of a news company and everyday, he receives tens of applications for the post of some type of journalist from engineering graduates.

8:47 AM

Ok, an engineering degree isn't an obvious qualification for journalism :-)

user228700

Exactly. Some others become auto/car drivers.

But if there is pressure on schoolchildren to go into engineering that means a sizeable proportion of them won't be much good ...

user116211

I'll open a casino in future.

user228700

And since we're speaking about misemployment, I must mention something that happened to us (my family) a few months ago...

@MAFIA36790 now that's the way to make money :-) Just as long as you have a good grasp of probability!

user116211

8:49 AM

@JohnRennie yeh; It should be Quantum Casino.

user116211

No Boolean probability is allowed.

@Kaumudi Yes ...

user228700

We had been travelling to the railway station in a cab. The cab driver was friendly and began to speak about the political situation here, in Tamil Nadu.

user228700

From his structured and complicated opinions regarding the current state of things, we immediately guessed that he was well educated. The traffic was terrible and as we got to know about him more, he told us that he is a doctor...of psychology. Then again, he graduated from one of the colleges here, so obviously, there wasn't much scope for proper employment but still. He's got an effing PhD and he goes around driving a cab. It was one of the most horrifying moments of my life, tbh.

user228700

This speaks volumes, mostly just about how amazing our colleges are.

user228700

8:58 AM

What, no comment? :-P

user116211

Well, now I'm feeling more motivated to open a casino.

user116211

O maybe I should join a gang in Mexico ;/

user228700

@JohnRennie?

user228700

@MAFIA36790 Lol, maybe you should. Teach them some physics while u're at it.

GPhys

oh god

I always forget all my commutator algebra Q_Q

9:12 AM

@Kaumudi I can't comment. The impression I get is that India's economy is booming, and under those circumstances there's rarely a shortage of employment.

user116211

@JohnRennie We need commies now.

user228700

@JohnRennie Sigh, yes, I guess. But there is a lot more to it than that and I'm not qualified to explain it.

GPhys

my usual strategy is to quietly calculate the poisson bracket and hope the answer isn't something like $xp$

or do silly algebra tricks :D $[x^2,p^2]=[x^2,p]p+p[x^2,p]$

yuggib

what else do you want to do?

user228700

@JohnRennie: Are u busy atm?

9:24 AM

It would be cool if the jacobi identity has some interesting geometrical meaning. I mean, the way the three terms are cyclic permutation just screams it is something ROUND

9:34 AM

@Kaumudi I'm sort of doing a few jobs, but if you have a question I can probably squeeze it in :-)

user228700

Thanks :-) I think it's OK; Martin over at CSE chat has (hopefully) got me covered for this one...

user228700

9:58 AM

@MAFIA36790: U there?

user228700

Oh, crap.

user116211

10:15 AM

What?

To start with: Time first loops

and then space started to squish

It's all making sense now, finally ,after 8 years

What are you looking at? It is of course a god dang CTC!
The tesseract spacetime is predestinating its own collapse

Nope, they got it wrong, tesseract honeycombs only allow apparent teleportations (as seen form our 3D persepctive) and only a limited extet

10:53 AM

Actually, not parallel reality nor alternate timelines, but the same worldline crossing itself (or at least somewhere near) many times. Damn, Slereah is going to love all those CTCs in this thing!

The Spherical Droste Effect, with added twist and recursion.

11:13 AM

Please explain spacetime geometry that can give rise to such stroboscopic effect

IT is unsure if it is even meaningful to plot the timeline of events of this movie. but one thing is clear, the spacetime of this thing is NOT a tessrect.
The spatial part may be, but definitely not the spacetime

heather

11:32 AM

@JohnRennie, I'm very interested in your proposal (for the homework site) but I'm wondering if really there should just be a reformulation of the homework policy such that some homework questions - like the ones you are interested in - are allowed. There has been debate over whether engineering questions or math-y questions are closed too quickly, and so I think it's worth looking at to see if that's feasible.

If it isn't possible, I would be interested in helping/supporting the new site, though I'm not sure how much I could help.

Another thing worth considering is whether it will turn into a situation similar to math and math overflow, in which case I'd whole-heartedly disagree (this is also why I'm wondering about incorporating it into physics somehow).

Emilio Pisanty

12:04 PM

Yo @JohnRennie, check this out

Q: Moments around a pivot system.

user116211

12:40 PM

0

Vane mounting System: Question 1: Take the moments about P for (a): My answer: $Sb = g(aM + cm)$ Though I think this is wrong since I don't know how to incorporate the $P$ force. Question 2: Take the moments about P for (b): My answer: $Sb + Ra = (x+a)Mg + cMg $ Can anyone help me, this ...

forces free-body-diagram

user116211

Homework?

user116211

Does Hillary's victory guarantee a nuclear war?

user116211

Karlsruhe neutrino mass experiment has been turned on

user116211

Anti-West terrorists are steps from crippling South African universities at least for a semester

user116211

A Cambridge video introduction to strings

user116211

12:47 PM

I love his blog :)

user116211

1:06 PM

0

Q: Daughter (9) wants to demonstrate quantum physics for Science Fair

That's pretty much it. This is the result of a kid's book in which a boy goes searching through parallel universes to try and find his dead mother, and there are explanations of Schrodinger's Cat and quantum entanglement along the way. I am an arts graduate and clueless: the project is supposed...

quantum-mechanics education

user116211

I'm voting to close this question as off-topic because there is no actual conceptual query in it. — MAFIA36790 1 min ago

user228700

1:48 PM

@IanEmnace: Is this you:

user228700

Was watching the video and this is one of the top comments...I thought I'd seen that picture before. Isn't that the same as ur avatar?

Ramanujan

@Kaumudi possible duplicate. (lol)

3:12 PM

@ACuriousMind What is the intuition for the smash product?

"One can think of X ∧ Y as a reduced version of X×Y obtained by collapsing away the parts that are not genuinely a product, the separate factors X and Y."

What does that even mean?

@0celo7 It's just gluing two pointed spaces together at their basepoints.

@ACuriousMind That's the wedge sum, no?

@ACuriousMind Yes, that's the wedge sum.

So what is the smash product?

Eh, I always mix these two up. The smash product is the quotient of the product by the wedge sum. I'm not sure there is a better description of it

For example, $S^m\wedge S^n$ has a cell structure with just two cells

wtf

How am I supposed to prove this stuff?

Smashing Pumpkins on "Muppets Tonight"

The sentence you quoted means to say that the wedge sum is not "genuinely a product", it's just the original spaces sitting inside the product.

So quotienting it out gives you everything that the product "adds" to the original spaces

Slereah

3:18 PM

possible informations on the smash product :

@ACuriousMind Ok I need to learn how to algebraic topology

I'm a damn analyst, how does one prove stuff via pictures??

@ACuriousMind so an n sphere is two n cells glued together, right?

yes

So n sphere x m sphere has how many cells?

btw, do not expect any deep insights from me today, I'm sick and my thoughts are moving rather slowly :P

Sorry, hope you feel better

3:25 PM

thanks

@0celo7 Four

You take all cells $e_\alpha$ from one complex and all cells $e_\beta$ from the second one and then take all possible combinations $e_\alpha\times e_\beta$.

bolbteppa

Should I stop studying lie algebras and learn how to write the relativistic point particle in terms of twistors, it's right there :'(

Then you do the same for the gluing maps, and there is your product cell complex

@0celo7 Wait

That is a possible cell structure for the sphere, but the canonical one is gluing an n-cell to a 0-cell

And the canonical one will let you figure out more easily what the smash product of two spheres is.

Are they homeomorphic?

@0celo7 Yes, it's basically the difference between an atlas with two hemispheres and the stereographic projection

3:43 PM

Hi all

hello

Congratuliations @ACuriousMind for getting the mod post, I tried to vote for you but I didn't have enough rep that time

@IanEmnace thanks