The h Bar

6:00 PM

@0celo7 sadly I'm about to slump into my armchair with a beer and my current book. I started work 11 hours ago so I'm fading now.

anonymous

Right. I get it :)

Balarka Sen

@0celo7 I think you won't like Gromov's writing

But it's coauthored so that's better

anonymous

@0celo7 What balls? I just realized that John's messages about combing hedgehog testicles are missing on the starboard for a long time :P.

Balarka Sen

probably

@anonymous Hairy ball theorem says you can't do that

skill patrol

(removed)

anonymous

6:04 PM

@BalarkaSen Hehe :'D

0celo7

why don't we call it the Kiwi theorem?

anonymous

Hedgehog testes aren't that hairy !

0celo7

@BalarkaSen Lee calls the ham sandwich theorem the "Tofu Sandwich Theorem"

@anonymous ...how do you know?

anonymous

@0celo7 I saw them

0celo7

Why were you looking at hedgehog testes?

The people deserve an answer

Balarka Sen

6:09 PM

busted

anonymous

@0celo7 I am really curious about the reproductive system. :'D

0celo7

just go watch some hentai, jesus

DanielSank

What do folks think of this comment

Without any idea of the noise sources (including the amplifiers), the question is useless in any practical sense. As a homework exercise, well, that runs afoul of the general homework policy. And the question is worded, well, horribly. — Jon Custer 3 mins ago

anonymous

@0celo7 That's gross

0celo7

and looking at hedgehog nuts isn't??

hey

6:10 PM

Hii

anonymous

@0celo7 -_- Hedgehogs don't wear clothes.

0celo7

you're hopeless

good luck in prison

anonymous

LOL. See you there! :'D

hey

Can I ask a chemistry question ? Of high school level

0celo7

@anonymous they won't take me alive

skill patrol

6:13 PM

Top of the world ma?

anonymous

@hey Go on!

0celo7

@hey we only allow PhD level questions in here.

hey

We have to find among the following in which dehydration can take place .

I think it should be first option as there would be resonance when carbon is formed.

0celo7

Oh god. Organic chemistry. It is allowed @hey

hey

Thanks man

@0celo7 do you love organic

anonymous

6:15 PM

@hey What is the reagent?

conc. H2SO4 ?

Balarka Sen

I think it should be (1) too. There's an intra-molecular hydrogen bond happening, so it's easier to extract up the water molecule, roughly.

0celo7

@hey Organic is PhD level chemistry.

Balarka Sen

I don't understand the resonance logic though.

anonymous

@BalarkaSen That is bad reasoning. Dehydration will destroy the hydrogen bonding if that happens. That is at best an hindrance and not a cause.

hey

@anonymous no reagent is given just asking maximum dehydration

Balarka Sen

6:17 PM

@anonymous Dehydration just extracts the H2O molecule: why should it destroy the hydrogen bond? I don't understand that.

hey

@0celo7 but there is a school level exam in which it was asked

Balarka Sen

If anything it should break the C-O and C-H bonds.

anonymous

@BalarkaSen Initially there is intramolecular H bonding but after dehydration there isn't.

0celo7

@hey not in America!

@ALL "Cookies and Cream" poptarts actually taste like Oreos

hey

@0celo7 in India there is such exam , if you have heard of it . IIT JEE

Balarka Sen

6:20 PM

@anonymous I don't see that as a sufficient reason. Maybe after the C - O and the C - H bond breaks, the attraction formed by the H-bond in H --- O makes them have a covalent bond?

Sounds plausible by common sense

"proof by common sense"

0celo7

@hey the JEE is insane by our standards

harder than college

Mostafa

@DanielSank I think he's right...the question doesn't talk about noise at all.

anonymous

Actually all of them can get dehydrated with (conc) H2SO4 as a 2 degree carbon is formed. But first option will provide conjugation with C=O.

So that would be my best bet.

hey

@0celo7 lol

vzn

@anonymous lol ~~pop science~~ ... are you a student? physics? what country?

anonymous

6:22 PM

@BalarkaSen "the attraction formed by the H-bond in H --- O makes them have a covalent bond?"....what do you mean? I don't really get you.

0celo7

@BalarkaSen I know you don't care for analysis but that parabolic PDE PEU is very interesting. Lots of applications to geometry (curvature flows).

anonymous

@vzn Yeah it is a pop science book :) We spoke earlier in Physics Meta chat room.

0celo7

@Mostafa Did you try to say something?

Were you silenced by the IIT?

oh god they killed him

vzn

@anonymous yes cant recall much or maybe you didnt say much :| ... fyi there are some excellent documentaries on LHC you might enjoy. also note that carroll book is pre-higgs discovery

Mostafa

@0celo7 Don't get fooled by the appearance...it's just lots of lots of techniques and things to memorize

Balarka Sen

6:24 PM

The H-bond acts as an attraction between the H and the O atom (indeed, it's about 1/10-th of the attraction happening with covalent bonds). After breaking of the C - H and C = O bonds, maybe the attraction gets them close enough for them to form a covalent bond by sharing of electrons?

That's all I meant

I personally don't understand your logic by conjugation, but then I don't know much about chemistry. If you want to explain I'll listen

0celo7

@Mostafa Memorization is so hard

anonymous

@BalarkaSen C = O bonds don't break during dehydration...

hey

@anonymous and @BalarkaSen answer is given as second option

Balarka Sen

@0celo7 Yeah, I heard.

@hey Strange!

0celo7

@BalarkaSen *PDE REU

Mostafa

6:26 PM

But it works for a good portion of the questions on these exams...

anonymous

@hey Yeah, that is the second best option as the first option hydrogen bond is destroyed inside the molecule.

Mostafa

@anonymous have you memorized the periodic table?

0celo7

> Therefore, the global existence and existence of solutions

anonymous

The (+) charge will be in conjugation after hydride shift

0celo7

Hmm.

Mostafa

6:27 PM

(I did)

anonymous

@Mostafa Yeah.

Balarka Sen

@anonymous oic. i dunno the mechanism

what happens?

anonymous

@hey That's what I and balarka were talking about. The initial hydrogen bonding inside the molecule stabilizes it so greatly that dehydration would make it somewhat less stable. But in the second option there is no initial hydrogen bonding.

Mostafa

@anonymous That's a good way to get round many time-consuming chemistry questions....

anonymous

@Mostafa Hehe. It is useful. True. But we are expected to know it anyway :)

Direct questions are never asked though.

Balarka Sen

6:30 PM

chem is strange and hard

Mostafa

The best (only?) way to get a high score is such exams to be prepared for difficult time-consuming analytical questions, solve them apriori and memorize the results. (and answer from your memory)

anonymous

Mostafa

@0celo7 I also memorized 350 words in 5 days for the general GRE 2 years ago.

anonymous

@Mostafa Doesn't work in JEE :P Good for school exams though :)

Chem is easy once you devote sufficient time to it.

I personally love organic chem :)

Balarka Sen

That's what I'm bad at

Mostafa

6:33 PM

Isn't chemistry the easiest subject of the test?

Yeah it is ^

JEE is insane.

i know right?

@anonymous Have you ever scored above 90%?

on chemistry

0celo7

You could be masters of PDE if you didn't have to devote all this time to trivial trivia.

That's what this seems like, trivia.

You're never going to use this.

anonymous

6:35 PM

@Mostafa In school I always scored above 90. In JEE advanced mocks never crossed 70-75 :/.

Balarka Sen

who wants to be masters of pde dude

that's a worthless goal

Mostafa

@BalarkaSen Isn't Classical Physics just study of PDEs?

Balarka Sen

do topology instead. cool pictures

0celo7

@Mostafa no

Mostafa

:|

Balarka Sen

6:37 PM

i certainly wouldn't want to be a master of classical physics instead though!

anonymous

@0celo7 Not everything is done for a goal. I personally love studying the JEE topics. I do the physics, chem and maths out of love. Scoring marks in the exam is secondary. I don't even want to be an engineer.

Bernardo Meurer

The best strategy to study is to give up

0celo7

@anonymous I love math but I would not want to study hard integrals

That's what the JEE seems to be like

Balarka Sen

@Bernardo yeah man who cares

anonymous

@0celo7 That's like saying I love cricket but I don't want to learn bowling.

Balarka Sen

6:39 PM

JEE is a good, hard set of puzzles. I wouldn't belittle it. I can't do half of them in finite time.

0celo7

I'm not belittling it

I'm saying puzzles are stupid

Bernardo Meurer

Honestly though, if you need good grades just accept it, sell your soul and bust your ass for a month solving problems until you get okay

Balarka Sen

But it is indeed not a good prototype of mathematics as done by the actual world

Bernardo Meurer

@BalarkaSen I'm taking topology this semester

Anything I should know beforehand?

Balarka Sen

Not all of math is puzzles.

Bernardo Meurer

6:41 PM

@0celo7 ?

Balarka Sen

@Bernardo A bit of analysis won't do much harm.

anonymous

It it weren't for the tough puzzles I wouldn't even appear for JEE. They provide the thrill. Just like olympiads. I have all my life to do mainstream maths. Why worry about it now?

0celo7

Why are you taking topology?

Bernardo Meurer

@BalarkaSen Already took that last semester

@0celo7 because it's on my Analysis II syllabus

0celo7

You're going to do metric spaces

Balarka Sen

6:42 PM

You should do Chapter 2 of Rudin if you really want to get an idea.

Bernardo Meurer

Holy fuck, Fantano rekd Future

Balarka Sen

@BernardoMeurer Good, then you're more or less ok

0celo7

Yeah he did. Did you not see my message?

Bernardo Meurer

@BalarkaSen I should have gotten that book and forgot

@0celo7 Yes, I'm replying to that

0celo7

Aha

Bernardo Meurer

6:42 PM

@0celo7 I told you already I got a new syllabus

Worse one possibly

Mostafa

@BalarkaSen I don't like solving over 200 multiple choice problems in 4 hours. I like focusing and thinking on one problem in that time.

0celo7

I feel like Fantano is just disappointed a lot

Balarka Sen

@anonymous Sure, that's fine. You should do whatever that makes you happy.

I have personally never felt the Olympiads, or JEE type problems very interesting.

Maybe momentarily, but not for a long time to stick to it

Mostafa

@BalarkaSen I love classical physics!

just starting to read this:

press.princeton.edu/titles/10157.html

2

Balarka Sen

@Mostafa You shouldn't do it then. Focus on what makes you happy.

Bernardo Meurer

6:47 PM

God, I hate Quavo

Lil Uzi scares the shit out of me

Mostafa

> In this book, a central theme will be a Geometric Principle: The laws of physics must
all be expressible as geometric (coordinate-independent and reference-frame-independent) relationships
between geometric objects (scalars, vectors, tensors, ...), which represent physical
entitities.

0celo7

@BernardoMeurer QUAVO

Mostafa

From that book ^

0celo7

@BernardoMeurer what's wrong with Uzi now :(

Bernardo Meurer

He's a mutant

I like Post, he's kind and sweet

0celo7

6:50 PM

He's not the biggest mutant

Balarka Sen

@0celo7 did you ever hear the album i gave you

0celo7

Boat is a freak

@BalarkaSen no! Please send it to me

I was wondering about it the other day

Bernardo Meurer

It's like Yatchy, I hate him too

He sounds so stupid it hurts

Balarka Sen

there @0celo7

It's totally my favorite now, along with Earthling (the next album)

0celo7

@BernardoMeurer If you can't take the heat, get out the streets

skill patrol

6:52 PM

David Bowie is so...on the edge.

Bernardo Meurer

@0celo7 'Cause it get cold like Minnesota

Balarka Sen

@skillpatrol He's awesome

Bernardo Meurer

I like Bowie

Lil Yachty - Minnesota ft. Quavo, Skippa da Flippa

►

0celo7

@BernardoMeurer I think we're getting a Drake album this Friday.

Bernardo Meurer

I don't care for Drake

skill patrol

6:56 PM

@BalarkaSen how about pink floyd?

0celo7

@BernardoMeurer he is very monotone, I can't stand him on solo tracks

But his collabs are always excellent

Balarka Sen

He's a bag of crazy ideas. I mean the album I linked is about 7 different people or something involved in an underground crime hysteria about murder art, which is, in short, mutilation and making art out of the victims

@skillpatrol Haven't heard a lot by them but they're ok

0celo7

@BernardoMeurer check out Gucci Mane and Drake "both"

It's good

skill patrol

@BalarkaSen sounds like Edgar Allen Poe :P

Or the silence of the lambs

Balarka Sen

yeah, but darker. 1.Outside and Earthling is more or less a textural diary of the last couple years of the century (or millennium)

skill patrol

7:02 PM

(removed)

0celo7

What?

I missed it

DanielSank

Everyone stop.

john custer knows how to design Chebychev filters

@DanielSank - you always want your input signal range to be as close as possible to the ADC full scale (except of course when noise kills you). This is not a particularly deep physics question. And, as many find out, noise sources are the real limiter. On the other hand, I know how to design and build a 4-pole Chebyshev band pass filter... — Jon Custer 19 mins ago

0celo7

@DanielSank is this significant?

Mostafa

@DanielSank Only 4-poles? I can design with 6 poles and even more :P

@0celo7 It was about Drake appearing in Justin Bieber's Baby

Mostafa

7:20 PM

@101010111100 Here is one of my favorites: "The algorithm fathoms in a synergetic manner globally, and an antagonistic depth quest locally.". Whatever that means! — Coconut Feb 19 at 7:15

What does it mean? :/ ^

AccidentalFourierTransform

duh, it means that the algorithm fathoms in a synergetic manner globally, and an antagonistic depth quest locally

5

skill patrol

7:34 PM

Yeah! What else could it mean?

heather

hello all

skill patrol

hi

how are you?

heather

good @skillpatrol, yourself?

skill patrol

Fine, thanks.

AccidentalFourierTransform

@heather Hi there

who starred that?

skill patrol

7:39 PM

(removed)

AccidentalFourierTransform

once again, the starring patterns of this chat have proved elusive

5

:-P

¬¬

heather

lol

another devious twist in starring patterns

skill patrol

<.<

Balarka Sen

nah. predictable

skill patrol

>.>

AccidentalFourierTransform

7:42 PM

nah. predictable

Mostafa

( ͡o ͜ʖ ͡o)

skill patrol

predictable. nah

heather

o_0

AccidentalFourierTransform

Mostafa

The h-Bar's become chaotic...Where's ACM

skill patrol

7:47 PM

0_o

AccidentalFourierTransform

bye fellas

Bernardo Meurer

Wow

For once this wasn't my fault

DanielSank

@BernardoMeurer What, all the stars?

Mostafa

The room suddenly became unstable

heather

i think spacetime is dilating around this room...

Bernardo Meurer

7:55 PM

@DanielSank Something to do with the Big Bang or something. Like it all exploded and then we got stars from that when the universe was born

skill patrol

@heather time is the one that dilates

(removed)

Bernardo Meurer

These mods are removing everything

Mostafa

What's going on? who's starring everything?

Danu

I think I'm gonna go ahead and remove these random stars

Mostafa

can you?

Bernardo Meurer

8:04 PM

@Danu They aren't random, they are a scream against the oppressive regime we live in

@Danu The stars on the removed message were clearly a meta-joke

Danu

@BernardoMeurer You're probably semi-joking, but I don't think it is particularly funny. If you have a serious complaint about the PSE moderators then do something with it; if not, maybe just consider cutting it out.

Bernardo Meurer

@Danu You'll never know, I'm the Schrodinger critic

Never know... what?

@Danu Exactly.

:)

8:12 PM

:)

0celo7

8:24 PM

@ACuriousMind you should be proud of me. I just went to a seminar on linear algebra and algebraic geometry

Danu

Seminar on linear algebra?

So how'd they apply algebraic geometry in linear algebra (or vice versa?!?!)

DanielSank

I tried to take a course on algebraic geometry once.

It sounded so awesome, but I didn't understand the first lecture so I didn't take it.

I was sad.

Danu

Haha

Was it more classical algebraic geometry

or more like schemes and stuff?

DanielSank

As I said, I didn't understand it.

Schemes? I don't remember any schemes.

I remember a sheath or some such thing.

Danu

@DanielSank Sometimes they tell you something about the general outline of the course at the start :P

@DanielSank Sheaves

That sounds like classical stuff. Really nice and beautiful

I know a little bit about classical algebraic geometry but none of the more modern stuff

But I think you can also do a lot of sheaf stuff in the more modern approach

so who knows what you were subjected to

DanielSank

8:30 PM

I had posted a link that I was hoping would sit on the star board for a while. It had 6 stars, but was bumped by what looked some some other folks playing around with the stars.

So here's the link again

Danu

In any case, the concept of a sheaf is not TERRIBLY hard---it just seems a little bit of an unnatural thing until you get a big picture kind of understanding of what kind of problems they are used to solve (again, in classical alg. geom.)

DanielSank

Homework policy meta draft

4

Balarka Sen

I think sheaves classically came up from complex analysis

also I think you're using the term classical algebraic geometry for complex algebraic geometry

Danu

Yeah, they were definitely useful in the theory of Riemann surfaces

@BalarkaSen But isn't that what the classical stuff is?

David Z

@DanielSank One comment: I don't support saying that the highest-voted proposal will be used

Danu

8:32 PM

(mostly)

0celo7

@Danu Well, it's the analysis seminar, so it was about von Neumann algebras

Balarka Sen

Well, I just mostly think of the classical stuff as varieties.

0celo7

But he was only considering finite-dimensional ones

Balarka Sen

The story is actually sort of subtle over arbitrary alg closed fields than C

Danu

@BalarkaSen Okay, but that's essentially complex alg. geom., isn't it?

DanielSank

8:32 PM

@DavidZ Can you drop a comment on the document, please?

Balarka Sen

@Danu Over C

Danu

@BalarkaSen I see

0celo7

But he didn't explain what he was doing had to do with those

David Z

@DanielSank sure, later

0celo7

He's studying hadamard matrices

DanielSank

8:33 PM

@DavidZ Thank you.

Danu

Fair enough---I come at it from an "(algebraic) GEOMETRY" kind of perspective of course @Balarka :)

0celo7

And those lie on varieties, apparently. But he forgot the word for variety and kept calling them "manifolds"

Balarka Sen

@Danu Yeah. I dunno much about anything so take my opinion as a grain of salt anyway!

Danu

@0celo7 Maybe he actually meant manifolds?

@BalarkaSen Actually

0celo7

So people kept asking him what these things were supposed to be

@Danu nah, he corrected himself eventually

Danu

8:34 PM

Do you know anything about whether other kind of fields are interesting from a topology/geometry perpsective?

Are finite fields useful at all?

0celo7

But my topology prof eventually erupted with "AH, they're varieties," and all of the analysts in the room were still clueless

HDE 226868

@JohnRennie Strange but true. Upvotes get you no reputation points, but bounties and, I believe, acceptances do.

0celo7

Anyway, not very interesting. But I want to see the sequel

@BalarkaSen what's a hopf algebra?

Balarka Sen

@Danu Oh yeah the story for finite fields is very much interesting even though I know absolutely nothing about it. There's the Frobenius endomorphism story (basically counting fixed points of a diophantine eqn over a variety over F_p^n), and eventually gives you a Lefschetz-like formula

Danu

@BalarkaSen I'm looking for applications to geometry/topology (of the smooth kind)

I'd really like to find some sort of good motivation for all the algebraic stuff

Balarka Sen

8:37 PM

@0celo7 It's both an algebra and a coalgebra. You have a multiplication $X \times X \to X$ and a comultiplication $X \to X \times X$.

Danu

But so far I can't escape the feeling that it's more for its own sake (more general versions of originally geometric ideas etc)

0celo7

@BalarkaSen comultiolocation? (Wow autocorrect doesn't even try on that one)

*comultiplication

Balarka Sen

@Danu Ah, that is much harder. The best I can do is present it to you as a "generalization" of what happens in $\Bbb C$ to what happens in other fields. Indeed, through most of the algebraic algebraic geometry I learnt I took that as a motivation: take a theorem in complex. Is it true in arbitrary fields? To what extent? How does the picture generalize?

That finite field story, eg, gives you something unexpectedly topological (the Lefschetz fixed point formula)

Danu

@BalarkaSen Yeah, but for me that in itself does not sound so attractive, somehow.

Not to sound too dismissive or anything

I just don't know any reasons to care, you know?

Balarka Sen

I understand that feeling.

I went through a lot of that when I started learning this stuff. But in the end I found it a fun endeavor.

Bernardo Meurer

8:43 PM

@Danu I'm not a civil engineer

David Z

@heather They do. But community approval measures popularity, not directly whether a proposal is good or not.

0celo7

8:55 PM

@BalarkaSen pls talk to me about hopf algebras

They will show up in the next analysis seminar

Balarka Sen

@0celo7 what do you wanna know

0celo7

What a comultiplication is. I googled it and got a commutative diagram. I don't think in terms of those...

Balarka Sen

@0celo7 It's a certain map $X \to X \times X$. I mentioned that before.

0celo7

@BalarkaSen yeah, I saw that. What does it do?

heather

i think this could be mod hammered

0

Q: About composite materials

Dear everyone I am so happy if somebody can help me to deal with these equations.

particle-physics

skill patrol

9:00 PM

How was Chicago? @0celo7

0celo7

@skillpatrol mostly good

Balarka Sen

@0celo7 It can do literally anything, except that there's an identity. I forget what the right notion of that is but I think it's that there's an $e \in X$ such that $h(e, x)$ and $h(x, e)$ are both identity.

@0celo7 Sorry, sorry, total garbage. Forget I ever said that

So I think identity is a map $e : X \to X$ instead.

skill patrol

Popcorn is served.

Enjoy

Did you decide on the textbook yet? @BernardoMeurer

DanielSank

bye, everybody

Bernardo Meurer

@skillpatrol No. I asked the prof and he just made it worse

skill patrol

9:15 PM

Cya

heather

@DanielSank, have a good day.

Bernardo Meurer

he told me to get the Giancoli, then Daniel told me to get kleppner and kolenkow, and someone here said Halliday

So now I have no clue

skill patrol

Did the prof suggested Giancoli? @BernardoMeurer

Bernardo Meurer

@skillpatrol Yep

But that one has "For Engineers" in it

I hate that

skill patrol

Which is the cheapest?

vzn

9:20 PM

@DavidZ btw thx for plugging the special guest session in regular mtg, wasnt able to make regular mtg, wanted to :(

skill patrol

@BernardoMeurer rob suggested a good one.

Danu

@BernardoMeurer Giancoli sucks, I must say.

Bernardo Meurer

You guys are going to make me cry, I swear

Danu

There's a nice color-and-everything version on da webz

Bernardo Meurer

Everyone likes a different book and thinks another one sucks

skill patrol

9:34 PM

What was the name of rob's suggestion?

Bernardo Meurer

I'm trying to find it in chat search but there are too many robs

DanielSank

@BernardoMeurer Theif!

0celo7

@BalarkaSen Are you here? I want to talk about $P^2\vee P^2$

Balarka Sen

go ahead

Bernardo Meurer

@DanielSank It's on my passport

skill patrol

9:47 PM

Feb 10 at 1:21, by rob

@BernardoMeurer We teach our freshman majors out of Chabay and Sherwood. Every time I reread a chapter, I think "Yes, that's totally how real physicists think about this sort of problem." I like that text a lot.

Bernardo Meurer

@skillpatrol Right, that's the one that's worth it's weight in gold

skill patrol

You gotta pay for quality.

0celo7

@BalarkaSen So the universal cover is just $S^2\vee S^2\vee\cdots$, but what exactly is the group action? I guess one should pick some distinguished two spheres first, then the generators move the spheres from left and right to the middle, alternating?

Balarka Sen

@0celo7 You mean to say, the action of $\Bbb Z/2 * \Bbb Z/2$ on this? Mark the infinite chain of spheres by even and odd numbers resp. The first copy of $\Bbb Z/2$ acts by antipodal map on some fixed even sphere, while flipping the two infinite chain of spheres attached at antipodal points. Same with the second copy with odd spheres.

David Z

→ 186 messages moved to Physics Meta

Hopefully I got all the right ones, let me know if not

heather

9:55 PM

some popcorn stuff got in there

Balarka Sen

who cares

heather

and your move to the meta room comment's there

David Z

@heather I thought that was part of it :-P