The h Bar

As otherwise (even if you have defined the multiplication to work like the scalar mutlpication) you get SQUARED the scaling of your coordinate system as you change coordinates

user116211

amazon.in/FOUNDATIONS-DIFFERENTIAL-GEOMETRY-CLASSICS-LIBRARY/dp/…

which I must say, might be an interesting sight

user116211

Quite cheap and export-friendly too, @0celo.

user116211

5:17 PM

@0celo7: I didn't know India is that good.... just other day we were discussing some weird sides of the country.

The only problem with these indian versions is that the covers are generally hideous

and I've heard mixed reports about print quality

although you get what you pay for

cover is fine

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@BernardMeurer they use black-and-white images of the international editions to reduce the price.

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@0celo7 Beautiful!

@MAFIA36790 This geometry book has no pictures.

5:18 PM

That's a nice cover

So that's irrelevant.

The print quality is pretty terrible though.

@IceLord I'm back. Did you solve your problem?

user218912

yes

that happens on quite a few pages

What's up, Bernie?

user116211

5:21 PM

The recent parliament decision was that the fact that a book is not meant for export has to be written at the front cover and not in the back and in a red background; so, it's weird why that is written so small in the back @0celo.

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@0celo7 ohh.

@DanielSank Just being an angry granpa

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Even if the book is not exportable, it is explicitly mentioned at Amazon; I didn't notice anything in the site.

because Apostol is 300 USD in US amazon

user116211

15 mins ago, by Bernard Meurer

I ain't paying 300 bucks

user116211

5:23 PM

I suggested him to export the cheaper Indian versions.

user116211

Although they are not export-friendly.

@BernardMeurer that's terrible.

@MAFIA36790 The best print quality by far are AMS books.

@BernardMeurer Go get the library's copy.

@DanielSank How do they expect a student to pay that?

user116211

5:24 PM

But if @0celo7 can export, I'm sure @Bernard can also.

Then "lose" it and pay the fine. It;s probably less than $300.

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@BernardMeurer Is there any EMI facility?

@DanielSank That's not right man, I'll just get the 20 dollar indian copy

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@0celo7 I've not read so far; but I would name Dover.

@MAFIA36790 EMI?

5:25 PM

Dover are paperbacks @MAFIA36790

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@BernardMeurer yes; we have that facility.

Dover has very nice print quality

I have ~5 dover books.

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@0celo7 How are they so cheap?

B.c. they're paperbacks from authors who are dead or don't own the copyright

5:26 PM

@BernardMeurer Fair enough.

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@0celo7 ah!

@0celo7 Does the copyright really matter?

Well Apostol is dead

I've always wondered where book purchase money goes.

Equated monthly installment

@DanielSank According to my prof who wants to write a book, not to the author.

user116211

5:26 PM

An equated monthly installment (EMI) is defined by Investopedia as "A fixed payment amount made by a borrower to a lender at a specified date each calendar month. Equated monthly installments are used to pay off both interest and principal each month, so that over a specified number of years, the loan is paid off in full." It further explains that, with most common types of loans, such as real estate mortgages, the borrower makes fixed periodic payments to the lender over the course of several years with the goal of retiring the loan. EMIs differ from variable payment plans, in which the borrower...

user218912

@DanielSank I didn't completely finish the problem because I just did some bs near the end to get the right answer even though i was off by 1/2

But the copyright can be sold to a big company like Wiley or Prentice Hall.

And then the author gets some money.

user218912

@DanielSank I solved the integral by using the orthonormality of sine and cosine.

@IceLord cool

@IceLord :|

@DanielSank Dover prints lots of stuff that's old and out of print.

5:28 PM

@0celo7 and?

user218912

@DanielSank just figured it out xD

Greetings and salutations, @JohnRennie

John Rennie

Evening all

@DanielSank I don't know. What was the question :P

@JohnRennie Hey!

user218912

5:29 PM

I had to divide the $\delta_{mn}$ by $\frac{2}{a}$ xD

@Danu are there things in life that are related to complex manifolds?

@DanielSank Aren't greetings and salutations the same thing?

@MAFIA36790 Kobayashi-Nomizu are recommended if you like geometry and Bourbaki.

@IceLord No idea what you're talking about, but great!

@DanielSank String theory.

5:30 PM

This circuit problem from a previous user got me curious, cannot really figured why the voltage dropped will differ when the switch closed unless the cell has internal resistance

i.imgur.com/Zr8XpaF.png';

Dudes this jazz is balling

@Secret What's the actual question?

1 hour ago, by MadRabbit

Hey guys, I know this is a really basic problem but I can't for the life of me figure out why flipping switch in this 'http://i.imgur.com/Zr8XpaF.png' circuit would change the output of voltmeter. Isn't the voltage equal when connected in parallel and as such it shouldn't make any difference if the additional 'branch' is connected as the voltage from the supply stays the same. Thanks.

@MAFIA36790 But be prepared to cry. KN is extremely hard to read.

i.e. Literally what I just said

5:31 PM

It's best read with 4 or 5 other books at hand to explain everything.

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@0celo7 Nothing is hard after you overcome Bourbaki.

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@0celo7 Very well.

@MadRabbit @Secret We need to know how much the voltage drops. Give numbers.

@MAFIA36790 That's...not true.

Bourbaki won't prepare you for Ricci flow.

user116211

5:32 PM

@BernardMeurer: ^^^

@Secret it's probably the internal resistance of the battery, but without numbers I can't say.

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@0celo7 Just kidding; but their treatment to logic is extremely dull.

John Rennie

@MadRabbit it's because the voltage recorded by the meter is the battery voltage minus the current through the battery times the battery internal resistance.

Great.

Besse's index is wrong.

The page numbers are all shifted.

So I guess if the battery is ideal then there will nto be difference in the voltage dropped then

user218912

5:34 PM

@DanielSank there's one thing in my finished solution I don't understand though.

user116211

EMI makes your life easy.

@MAFIA36790 ?

user218912

@DanielSank I read in a book that when you're squaring sine or cosine you write the second one with a different coefficient like m instead of n and then multiply them

AH

I see

user218912

why does that work?

5:35 PM

@IceLord Could you perhaps say that in math?

:)

user218912

like

@MAFIA36790 Do you have any AMS books?

I have a few, they're quite nice.

user218912

@DanielSank $\int [\sin(n\pi x)]^2 dx= \int \sin(n\pi x) \sin(m \pi x) dx$

I'm getting a Cambridge hardcover soon...wonder how nice it'll be.

Hopefully very nice because I intend on reading all of it.

user116211

@0celo7 Well, no; most are either Springer or Wiley. I have two books of Dover.

user116211

5:36 PM

@IceLord Horror; fix that!

@IceLord That's just plain wrong unless you're integrating.

also use \sin

user218912

sorry forgot the integral

user218912

why is it true when integrating? @0celo7 @DanielSank

@MAFIA36790 What Springer books do you have?

@IceLord I learned that in Freshman PDE class, I think you can figure it out.

@IceLord That's false.

@IceLord It's not.

user218912

5:37 PM

@DanielSank how I saw it in a book?

@DanielSank Are you sure

@IceLord You didn't.

@0celo7 Yes

user218912

I didn't?

@IceLord Go to a BadBadNotGood show if you have the chance

You probably saw this $\left( \int \sin(n \pi x) dx \right)^2$.

user218912

5:39 PM

no I'm sure it was like that.

:32397571 Would it kill you to not make irrelevant, confusing comments like that?

@IceLord There was something else going on

@DanielSank Yes, it would actually.

user218912

okay now i;m confused

Ok, I now know what was going on

Was there a sum over $n$?

user218912

YES

user218912

5:40 PM

I forgot to write that

user218912

dammit

user218912

and you can switch it to a sum like

user218912

$\sum_{m,n = 1}^n$

user218912

on the r.h.s.

I'll wait for you to write the whole expression.

I can't read your mind :)

Hi, @dmckee

5:43 PM

@IceLord Do you know what $\int_0^1 \sin(n\pi x)\sin(m\pi x)dx$ is?

Can you do the integral?

@MAFIA36790 Reading KN right now...praise be to cheap Indian books!

user116211

@0celo7 I have Bourbaki Set Theory; Axler's Linear Algebra; Callahan (although not mine); two books on first-order logic.

user116211

@0celo7 :)

Callahan?

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@0celo7 Multivariable Calculus.

user116211

not read that; but the pics are really good.

5:49 PM

Interesting.

user116211

Well, wait...

I wish I had lots of money, I'd just buy every book that looks cool.

@DanielSank Depends on what you mean by "life"

String theory uses it in an essential way to get 4d models.

user116211

@0celo7 I've ordered it; it will be shipped within a week. I have a borrowed one which I've not read it till now ;P

@BernardMeurer Part of it simply has to be "all that the market will bear". But there is a degree of complexity to the textbook market.

5:50 PM

When you want to go down from 10 to 4 dimensions you need to get rid of 6 dimensions (=3 complex dimensions) so you usually compactify on a three-dimensional manifold.

To get a "nice" effective theory in 4d, you need certain properties for this manifold.

The nature of the market for introductory astronomy books is probed in an article someone pointed me at:
www.phy.ohiou.edu/~tss/mercury.ps

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@dmckee so, why is the price different at different countries? I know there can be difference but the margin is quite high.

Yeah. Postscript. Sorry about that.

It turns out that if you want supersymmetry in 4d, you need a Kähler manifold, which is a manifold that is both complex and Riemannian, in a way such that the two structures are compatible.

@Danu How does that work in M-theory when there's 7 dimensions that need to go away?

5:51 PM

@MAFIA36790 Segmenting the market (i.e. making more money)

@Danu Indeed, I agree with that.

Looking like a good citizen to those not paying much attention.

@0celo7 You take one of the limits where it reduces to a 10d theory lel

I don't know jackshit about M theory

Perhaps this is where this whole story of $G(2)$ holonomy manifolds (which happens only for dim=7) comes into string theory.

Simple recognition that not everyone can actually lay hands on the going price in the post industrial parts of the world.

user116211

amazon.in/Advanced-Calculus-Geometric-Undergraduate-Mathematics/…

5:53 PM

@Danu By "life" I meant "stuff I might care about".

@DanielSank So, do you care about string theory?

That paper on astro books is an interesting read.

@Danu In that I don't know anything about it, no.

@DanielSank Then I do not know any applications :)

I do notice that in math more people are simply putting new books on the web.

5:54 PM

@Danu Ah. ok.

I'm honestly not too interested in applications

I'm going full math now.

@Danu Another one bites the dust.

user116211

@0celo7 As I mentioned earlier, I often use the EMI facility; it lessens the financial burden.

By pass the publishers all together, though I'm not sure that university bureaucracies are quite ready to treat that the same as "published a textbook" in the traditional sense.

Which is a concern for me, because I see the possibility of some of the stuff I prepare for students turning into a book in time.

@dmckee In any way, 300 dolars for a 666 page book?

5:56 PM

@DanielSank I see it more as leaving the physicists behind in the dust, but that's a matter of perspective ;)

And I'd like it to count towards a promotion in a big way.

user116211

@dmckee So, our community will have an author in you ;))

Perhaps. Eventually.

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@dmckee Good!!

Right now it is a collection of materials posted to a "Supplementary reading" folder on the LMS each semester.

5:58 PM

@Danu heh

user116211

Anyways, @dmckee, apart from Valter Moretti, do we have other authors as users in Physics SE?

Well, define "author".

user116211

@dmckee Who has a book related to academia , physics or maths in Amazon that is not out of publication ;P

We have blog authors. We have occasional participation for big name physicsist whose review articles are book like.

And so on.

@MAFIA36790 We have a user who has a vanity-press book on Amazon.

user116211

@dmckee I could name Lumo for his the Reference Frame.

6:01 PM

Vanity press is a lot cheaper these days then it used to be.

Concerning the edit: he'd assure you that it was.

user116211

Thanks @dmckee.

user116211

Yuggib also wants to write a book after his retirement....

@DanielSank Honestly, the transition is to a large extent due to some kind of... Almost intellectual dishonesty I've observed in the theoretical physicists at LMU.

Over the past year, I had a friend who was working---for his master's thesis---with "the most mathematical" people in the entire department.

It turns out that they don't really give a crap about understanding the background of the stuff they work on. Which is generally okay in physics, but the areas they work on are extremely demanding and interesting mathematically. Nevertheless, they mostly disregard that stuff. Even if they kinda know some of it, they just do not care.

In the case of my friend, I saw him slowly doing more and more "super advanced stuff" like computing Gromov-Witten invariants etc etc, without having even the slightest clue of what it actually was he was computing.

user116211

I'm off for now; night comrades.

It comes down to a sort of perverse return to plug-and-chug at the highest level. At least in his case.

I decided that I'd rather really know what I'm doing. Of course my actual enjoyment of mathematics also plays a role, and other factors do too, but the stuff I saw happening over the last year really made a difference in my mind.

/rant

6:17 PM

@Danu slow clap

You've summed up my thoughts on theoretical physics.

@Danu yep

user218912

6:45 PM

@0celo7 idk

user218912

what is it?

@IceLord I learned it in my Freshman PDE course

I think you should know it

user218912

please tell me.

user218912

we don't have a freshman pde course lol

user218912

it's 3rd year for me

user218912

6:49 PM

unless it take it next year which i will

If it's in Shankar...Lee

user218912

:o

I don't think it's in here...but we'll see.

Lol

found it.

user218912

page?

How much is it worth to you

user218912

6:51 PM

idk man

user218912

if my prof asks I can just be like

user218912

"that's well known fact"

user218912

and give some bs explanation

what BS explanation would you give

there is an easy way to do that integral

user218912

oh you're talking about that integral

user218912

6:53 PM

how do you do it?

yes.

user218912

okay you can tell me if you want but it's not that important to me to buy it from you.

user218912

right now i'm trying to figure out the dimensions of a canonical free scalar field in mass units.