The h Bar

John Rennie

12:00

@Blue suppose we want to run the app, let it work through some stuff then stop at the printf("line3")

Prathyush Poduval

@Blue I thought about it and realised that I had replaced the autocomplete features and all with manual googling, and now I feel it's a pain to do it now I've realised what I've been doing. So now I'm going to download VS the moment I get back home!

John Rennie

What we do is set a breakpoint by clicking in the left margin. I'll do it now ...

Anonymous

Okay so far

John Rennie

Hmm, why isn't it working ...

Ah, I wasn't clicking far enough to the left :-)

Anonymous

Now it shows the red dot

Anonymous

12:02

Yep

John Rennie

Now if we run the app (press F5) it will start running then stop where we've put the break point.

You try ...

Anonymous

Trying

John Rennie

There you go!

So with a big complicated app you can set a breakpoint at the bit where you think it's going wrong

Anonymous

Got it. Yes. Awesome :)

Anonymous

@JohnRennie Exactly

John Rennie

12:05

You can hover over variables to see their value

Fiv

@JohnRennie Are you busy?

John Rennie

@Fiv five minutes

Fiv

@JohnRennie Ok.

Anonymous

@JohnRennie Hover over where ?

Fiv

@JohnRennie I'm waiting then

John Rennie

12:06

@Blue Let me show you. I'll run it to the getchar then type an x

See. If I put the cursor over the variable a it shows me what a is set to

Anonymous

Yes , it does !

Anonymous

That looks useful

John Rennie

The VS debugger is just awesomely brilliant. You'll really come to value it when you're working on huge complicated apps!

I'll disconnect from your PC now. Hang on ...

Anonymous

@JohnRennie Hehe, yes :)

John Rennie

BOOM! I'm gone.

Anonymous

12:10

@JohnRennie lolol

John Rennie

If you installed Team Viewer you can uninstall it now or maybe keep it in case we need it in the future.

Maybe have a play with VS and do something a bit more complicated ...

Anonymous

@JohnRennie I'll keep it actually. It looks pretty useful. But thanks a lot for all the help :D

John Rennie

@Fiv I think we've finished playing with VS. What did you want to ask?

Fiv

@JohnRennie As first, It's too honorable to talk with you for me.

Anonymous

@JohnRennie Yep, sure

Fiv

12:12

I was gonna ask a question about nuclear physics.

Do you think the significants digits are important for atomic radii calculations?

John Rennie

If you do an experiment to measure an atomic radius then your experiment will always have some error i.e. the value you get won't be exact.

Fiv

is it better to use 3 significant?

John Rennie

When you're telling someone else what you measured you need to tell them how accurate your value is i.e. how many significant digits it has.

Fiv

@JohnRennie That was the most important thing for me!

I was thinkin about how they give wrong answers.

John Rennie

@Fiv The number of significant digits depends on how accurate your experiment was.

Fiv

12:16

and im seein the reason now.

what do you mean by tell them how accurate your value?

if you can show an example, it'd great.

John Rennie

Suppose I measure an atomic radius as 0.87654321 nanometres

But my experiment is only accurate to 1 picometer (i.e. 0.001 nanometres)

Fiv

you rounded it right?

John Rennie

That means the real value could be 0.001 nm less than my value or 0.001 nm greater than my value.

Fiv

so let's take a question

calculate the radius of iridium atom, given that ir has an ffc crystal structure, a density of 22.4g/cm3. and atomic weight of 192.2g/mol.

John Rennie

So it would be silly for me to tell people my measured radius is 0.87654321 nm. I would say it is 0.876 nm plus or minus 0.001 nm.

Fiv

12:18

What do i need to tell them?

However, they're giving wrong answers without telling them to solve it with 5 significant digits.

John Rennie

OK. You're given the density as 22.4 g/cm^3.

Fiv

Yes, absoulety.

John Rennie

That implies the error in the density is 0.1

i.e. the density could be as low as 22.3 or as high as 22.5

Fiv

it seems 22.4

John Rennie

Generally speaking if you're given a value you should assume there is a possible error of 1 in the last digit.

Fiv

12:22

oh got it now.

John Rennie

You're given the density as 22.4 not 22.40000

Fiv

Atomic weight is same too.

that's given as 192.2

John Rennie

Well you're given the atomic weight as 192.2 so you assume the error is 0.1 i.e. the atomic weight could be as low as 192.1 or as high as 192.3

Fiv

Yes, absoulety.

I'm gonna give them the avogadro's constant

as $N_{A} = 6.022 \times 10^{23}$

John Rennie

You have the density to three figures and the other parameters to four figures

Fiv

12:25

so?

John Rennie

So the error in the density is the biggest

Fiv

What would you recommend me to do?

John Rennie

When you're quoting the result you use the same number of figures as you have for the density

Fiv

The thing is everyone whom I'm asking this question gives anohter answers.

like 1.34, 1.35 and 1.36

the correct one is 1.36

Emilio Pisanty

@DanielSank "put a pin on X" = take topic X and pin it to the wall = let's talk about this at some other time

;-)

Fiv

12:28

I've been told that the reason they're giving different answers is significant digits.

What would you recommend me to do?

Emilio Pisanty

Fiv

I mean how should I ask this question?

Emilio Pisanty

^ one of my slides from Friday

@DanielSank @DawoodibnKareem, also CC @BernardoMeurer, that slide was prepared by inking in with a stylus on Power Point.

if there is a non-proprietary way to achieve that, then I'm all ears

Fiv

@JohnRennie Are you there?

John Rennie

@Fiv Well, what value do you get when you do the calculation?

Fiv

12:31

@JohnRennie I'm getting 1.34

However, that's not correct answer.

John Rennie

Give me a moment, and I'll do the calculation myself ...

Fiv

k

There's only an answer and that's 1.36

I wanna get the answer 1.36 when I ask this question to someone.

Slereah

@Fiv are you named after the feline immunodeficience virus

Fiv

lmao

John Rennie

Hmm, how are you doing the calculation?

i.e. what equation are you using?

ACuriousMind

12:39

I'm sorry to interrupt this conversation, but this user was, once again, a sockpuppet of a currently suspended user.

5 messages deleted

John Rennie

@ACuriousMind Oops :-)

Emilio Pisanty

@ACuriousMind ooof. I guess for some people there simply isn't any way to make them understand that sockpuppets really are not OK.

ACuriousMind

@EmilioPisanty Oh, I'm very certain the repeat offenders are perfectly understanding of the fact that socks aren't okay. They just don't care. :P

0celo7

@ACuriousMind can you say who the offender is?

ACuriousMind

@0celo7 I see no reason to

0celo7

12:54

👺

ACuriousMind

Google tells me that's a "Japanese Goblin Emoji". Truly, we live in a wonderful age.

Slereah

it certainly beat penis nose

John Rennie

If you ever feel the urge not to lower the tone don't worry that we would be disappointed :-)

3

0celo7

@JohnRennie is that English?

ACuriousMind

Why wouldn't it be?

Emilio Pisanty

13:04

@ACuriousMind I guess I meant "not OK" in the sense that their direct interlocutors find it an explicit breach of trust, more than just the abstract rules

0celo7

@ACuriousMind the words are English but the sentence sounds like Engrish

ACuriousMind

@0celo7 Just because its grammar is more complicated than the average American sentence doesn't mean it's not English ;P

You could perhaps argue it's not idiomatic, but then again it sounds very British in its indirectness to me

0celo7

What tone is he even talking about?

There’s also a double negative or something that doesn’t make sense

Please rewrite the sentence in simplified English in bullet points

heather

if you keep the tone [of your messages?] the same, we won't be disappointed

0celo7

What tone??

heather

13:09

no idea

=P

0celo7

Don’t worry, we’re just stupid Americans (MAGA)

Anonymous

@0celo7 Look at the message before JR's. You'll get it..

0celo7

No, I saw that message

So what?

Anonymous

So, umm, do I need to explain the message? :P

0celo7

I’m not sure what penisae have to do with this discussion but if you want to tell me that’s ok. I don’t judge

Anonymous

13:14

I'm not taking risks...lol

ACuriousMind

::chuckles quietly in the background::

CooperCape

@Blue if you were to say which book is better would you say the artin one or the axler one..

Cause I kinda want to get one in print cause I much prefer to read it

But idk which one now.

(Although the axler one is cheaper..)

Anonymous

@CooperCape Artin contains much more than Linear Algebra

CooperCape

Ahh okay... thanks.

Anonymous

Basically Linear Algebra+Abstract Algebra

CooperCape

13:23

(I'm just flicking through to contents of both)

Anonymous

BUT, another alternative to Artin is: Axler+Gallian

Anonymous

Axler is for LA

Anonymous

And Gallian is for the Abstract part

CooperCape

Hmmm

hard choices

Anonymous

Both are pretty nice and colorful (and easy to read)

CooperCape

13:24

(checks pricings)

Slereah

Hall talks about nice functions a lot

He should just make the set of nice functions

CooperCape

Galian is $$

Anonymous

I got Gallian for about Rs. 500 I think. Pretty cheap

CooperCape

hmmmm: amazon.co.uk/s/…

Anonymous

Around 6 British pounds i.e.

CooperCape

13:25

Oh wow

Anonymous

@CooperCape amazon.in/Contemporary-Abstract-Algebra-Joseph-Gallian/dp/…

Emilio Pisanty

@0celo7 John was telling Slereah, in British Euphemistic English, not to talk about penises.

Anonymous

If you're able to find a version of that on Amazon.com

CooperCape

Hmmm yeah

I'll look around

gah

Anonymous

@CooperCape amazon.com/Contemporary-Abstract-Algebra-Joseph-Gallian/dp/…

Anonymous

13:27

Found it

CooperCape

I'm beginning to think book companies don't like British people...

amazon.co.uk/…

that one right?

Anonymous

@CooperCape Yeah, but that looks too expensive. Order from Amazon.com instead

CooperCape

Yeahg

Or I might just get Artin as one book

Euugh

Prathyush Poduval

Why not get a tablet? It'll feel like you re reading from the real book (almost)

Anonymous

@CooperCape There's a bit of problem with Artin i.e. it doesn't have great typography...and not good for first time learning. BUT it is complete as a book and has most of the stuff you'll ever need in Algebra (for Physics).

CooperCape

13:30

Huuugghguhhg

I gotta go I'LL THINK ON IT

Anonymous

So some tough choice there :P

Anonymous

Good luck deciding

0celo7

@EmilioPisanty seemed like he was saying the opposite

Prathyush Poduval

@CooperCape aren't the books there in your library? (or any nearby one)

Anonymous

@PrathyushPoduval Reading technical books from a tablet is a bit of a problem for some people

Anonymous

13:32

I tried it...

Anonymous

Better to just download and print it, and then get it bounded

Prathyush Poduval

@Blue What kind of problems? eyesight?

Anonymous

@PrathyushPoduval Yeah, and some people just like scribbling on their books...like me

Prathyush Poduval

Yeah I always prefer the print edition, but if I bought all the books I wanted, my parents would be pretty broke

Anonymous

I don't feel like I've digested a book unless I scribble (notes) on the pages with a pen/pencil

Prathyush Poduval

13:34

Unless it's some marvelous proof, I don't write much on my books

@Blue I like my books to remain in the new condition

Anonymous

@PrathyushPoduval Printing and binding is actually pretty cheap

Anonymous

Just for Rs. 50 you can get any book bounded

Anonymous

@PrathyushPoduval Unlike me :D

Prathyush Poduval

@Blue I tried it once, price went too around 500

Anonymous

@PrathyushPoduval Where do you stay dude :P

Anonymous

13:35

It's dirt cheap here

Prathyush Poduval

Idk, it was a Xerox centre I went to. Where do you bind the books?

Are there specialised piracy shops?

Anonymous

@PrathyushPoduval Here

Prathyush Poduval

@Blue I thought you were talking about getting the books printed out then binded :P

Anonymous

@PrathyushPoduval No. I get it printed from my father's office printer for free. And then go there to get it binded

Slereah

"The problem with is idea is that the function exp[−ithk 2 /(2m)] is not a “nice” function in the usual sense."

He's very concerned about niceness

Emilio Pisanty

13:38

@0celo7 well, BEE does take some practice to master

Slereah

for a moment I thought you meant the other BEE

Emilio Pisanty

Brits often take a page from the Germans' Warum einfach, wenn es so schön kompliziert sein kann

Prathyush Poduval

@Blue I don't prefer the printouts. There's some feel to the book which you buy. Book>tablet>>laptop>>>>printout

I tried it once, didn't work out

Anonymous

@PrathyushPoduval Well, when you're broke, printouts seem the best....and I can't read math books from laptops or tablets

Anonymous

If it's a novel or something I might use a tablet to read

Prathyush Poduval

13:42

Feynman's book is great btw

0celo7

@Slereah good

Who is this?

Prathyush Poduval

The second half of his book is his adventures during the investigation of the challenger disaster

Anonymous

@PrathyushPoduval Oh, nice!

Slereah

@0celo7 Hall

Also he just used $\ll$

Physicist trash!

Emilio Pisanty

@Slereah you're French

you use « and »

Slereah

13:47

Not really

Emilio Pisanty

I don't see how you can complain about $\ll$ with a straight face

Slereah

They're not available on French keyboard

Emilio Pisanty

@Slereah no need

> In Microsoft Office applications, typing the US quotation mark (on the 3 key) will produce either a left Guillemet "«" or right Guillemet "»" based on the spacing.

Slereah

What kind of dork uses Microsoft Words

Emilio Pisanty

@Slereah >95% of French computer users?

Slereah

13:52

Dorks the lot of them

Emilio Pisanty

ah

Slereah

15:00

Hall have mercy

Stop using results from the future

he keeps talking about the spectral theorem

Two chapters from now

0celo7

@Slereah :(

What page are you on

Slereah

119

"Now, a physicist would say that the operator A in (6.1) does have eigenvectors, namely the distributions δ(x − λ)."

Damn physicists!

"The operators of interest in quantum mechanics, however, are not compact."

Isn't spin compact

bolbteppa

15:16

How do you remember the integral representation for the unit step function $\theta (t - t') = - \lim_{\varepsilon \to 0} \frac{1}{2 \pi i} \int_{-\infty}^{\infty} \frac{e^{-i\omega(t - t')} d \omega}{\omega + i \varepsilon}$ :(

ACuriousMind

@Slereah Yes. But the "operators of interest" here are more likely position and momentum :P

bolbteppa

Oh

Slereah

@bolbteppa Looks like the scalar field propagator!

bolbteppa

Derivative of Dirac delta function

Just remember Dirac delta, or scalar propagator yeah!

Hall is that rigorous qm book right

He mentions projective representations in there, which is a gold star for it

Slereah

yeah

It's not like 100% rigorous math

But much more than a typical QM book

bolbteppa

15:21

I even forget how to derive the Dirac delta from nothing and have to check notes :(

Slereah

what do you mean derive the dirac delta

I need to read Hall to read Reed and Simon

But Hall references Reed and Simon

End my life

bolbteppa

Derive the expression for it's Fourier expansion $\delta(x - x_0) = \frac{1}{2 \pi} \int_{-\infty}^{\infty} e^{i(x - x_0)t} dt$ one should know like the back of their hand

Slereah

I guess take that

Apply it to a function

Switch the integrals?

Check that $$\int \int dt dx e^{i(x - x_0) t} f(x) = f(x_0)$$

bolbteppa

I found a way to get it from the sinc integral which takes ages, that switching thing rings a bell as well

Sir Cumference

Sigh, there needs to be a way to trade hats

Slereah

15:26

they're not pokemons

Sir Cumference

@Slereah Then we need a battle system for hats too

bolbteppa

The reason I can't just sit down with Reed and Simon in a room and nothing else is the theorems are not motivated enough, e.g. who cares about Hahn-Banach, but it's not a fault of R&S, really well written what it does do, so I'm kind of side-prepping that book periodically

Slereah

@bolbteppa This equation is equivalent to the integral of the Fourier transform of $f$

I think by using some properties of the Fourier transform you can get the appropriate thing

bolbteppa

I think Zee does that switcharoo thing and I glossed over it

John Rennie

@0celo7 admittedly I grew up hearing that type of construction so I'm used to it, but was it really that hard to parse?

Slereah

15:29

Decompose it as like

$$\int dt dx e^{i(x - x_0) t} f(x) = \int dt dx e^{ix t} e^{-i x_0 t} f(x) = \int dt e^{-ix_0 t} \hat f(t)$$

Which I think gives you back $f(x_0)$

badaboom badabing

i probably forgot a bunch of factors but that's the sketch

bolbteppa

Yeah I should go over that method properly

Slereah

You can also do the physicist way

$$\int dk e^{ikx} \delta(x) = e^{ik0} = 1$$

Hence the inverse transform is just $$\delta(x) = \int dk e^{ikx}$$

But that is turbo physicist proof

bolbteppa

That's pretty awesome

Slereah

(Spoiler $e^{ikx}$ isn't a test function)

It's not even of fast decay!

Slereah

15:58

" the spectral projections being provided by a projection-valued measure and the functional calculus being provided by integration with respect to this measure"

Oh no

"The reader who is willing to take things on faith can simply take in the examples of the position and momentum operators in Sects.6.4 and 6.6 and accept these as prototypes of how the spectral theorem works."

I BELIEVE

bolbteppa

At least Bourbaki put in very small writing the examples which use material not in logical step with the previous material, I can't read books which do that kind of thing with a straight face

0celo7

@Slereah the book is very rigorous past like chapter 7

John Rennie

16:18

@Kaumudi.H Since you asked:

On the left is chicken in breadcrumbs, in the middle is sweet potato in a spicy batter and on the right is pepperoni and tomato in a pastry shell.

Posh chocolate biscuits for dessert.

ooolb

16:58

delish

DanielSank

@EmilioPisanty Inkscape, gradient fill

John Rennie

@ooolb it was a very nice meal. I am currently finishing it off with some after dinner mints.

ooolb

what kind of mints

John Rennie

Mint crumbles.

I think they are made by pressing icing sugar into a mould under a high enough pressure that it forms a firm solid. Then when you put them in your mouth it rapidly crumbles to release the peppermint flavour.

Captain Bohemian

17:15

I am eating white pepper biscuits.

CooperCape

yo ho ho

Captain Bohemian

I eat them because I feel so cold,

I also have a bag of garlic peanuts nearby.

dmckee

17:31

@0celo7 Example a highly-multiple negatives from literature: goodreads.com/quotes/…

I would guess that is Adams making fun on that idiomatic style.

John Rennie

The English have long understood that language can be an entertaining toy to play with.

CooperCape

@Blue (you probs don't care but...) I went for Axler/Gallian combo

I just preferred the look of them - and I felt you were right about Artin, it really doesn't look for beginners at all!

Balarka Sen

Language is a virus from outer space

CooperCape

Extra-terrestial live has been found in the form of language

Emilio Pisanty

@DanielSank what?

I don't mean the background

I mean the math

John Rennie

17:38

@CaptainBohemian I hadn't heard of white pepper biscuits before. Do you mean Pfeffernüsse

Prathyush Poduval

@CooperCape wise choice with axler, a wonderful book

CooperCape

It looks quite nice and I liked the contents

Also in response to what you said earlier about libraries the closest is 15mins drive away and I'm too young to drive :c

Prathyush Poduval

what about your school?

CooperCape

Won't have it

I looked around...

Prathyush Poduval

maybe convince the librarian to buy it...

CooperCape

17:48

Nah I have four brothers divide the cost by four and it's reasonable! (for christmas...)

Prathyush Poduval

@CooperCape Yeah, which is also why I didn't like artin much it looks quite old

@CooperCape all your bros are interested in the same stuff?

CooperCape

@PrathyushPoduval Nah... they all over 25... I mean't like they by 1/4 of the book each for me :)

Artin looked like a book that would de-motivate me...

Prathyush Poduval

kek, no christmas presents for you then :P

Captain Bohemian

Prathyush Poduval

@CooperCape Artin is the book you might need in the future

Emilio Pisanty

17:50

Is @BernardoMeurer or any other linux-knowledgeable person around?

I want to know what repo my machine is getting google chrome from

CooperCape

@PrathyushPoduval That's why I was considering it - But I guess they might have it in a uni library (at least they should, right?)

Prathyush Poduval

Yeah they should

are you accepted anywhere yet?

Captain Bohemian

@JohnRennie they look different from Pfeffernüsse.

CooperCape

Bristol, Exeter and Manchester

(I'm an official Oxford reject now!)

Prathyush Poduval

oxford?

oh okay

CooperCape

17:51

lol yah

Prathyush Poduval

you applying next year, or taking from your current choices?

CooperCape

But Macnhester's got Brian Cox! (that's not why I like it...) and I really liked their course

I think I'll go Manchester.

I wasn't too bothered about Oxford.

Prathyush Poduval

Hey @JohnRennie, I've decided to format my laptop. There's a option to have a fresh start which keeps my personal files and removes all 3rd part software etc. Is it alright to do it like this?

Emilio Pisanty

@PrathyushPoduval ... OS?

Prathyush Poduval

@CooperCape liked it in the sense, the syllabus or proffesors?

@EmilioPisanty Windows 10

CooperCape

17:53

Both kinda... They have a ton of research groups and the extra options throughout seemed really good.

Prathyush Poduval

Is it a 4y or 3y course?

John Rennie

@PrathyushPoduval "Fresh start"? Is that an option offered by the manufacturers recovery DVD? I don't recall anything like that in the regular Win10 install.

CooperCape

@PrathyushPoduval I applied for four year

John Rennie

@PrathyushPoduval ah, you mean this?

Prathyush Poduval

@JohnRennie Settings->recovery option->Learn how to start fresh with a clean installation of windows

@JohnRennie Yeah

(btw, how do you add hyperlinks in chat?)

CooperCape

17:56

[text](link)

John Rennie

@PrathyushPoduval I've never used it, but what I would say is that the most stable option in the long term will always be to completely wipe the disk and do a bare metal install.

Prathyush Poduval

@CooperCape [okay thanks](www.google.com)

CooperCape

hmmm

Prathyush Poduval

doesn;t seen to work

@JohnRennie How do I do that?

CooperCape

cc

Uhh

[cc](www.google.com)

that link don't work?

ACuriousMind

17:57

@PrathyushPoduval You need the protocol, i.e. the https:// part.

Prathyush Poduval

okay thanks

yeah got it!

@JohnRennie and also, is partitioning the hard disk recommended? (I have around 3 in total)

DanielSank

@EmilioPisanty Ok then just use the drawing thingy in Google slides?

Or Inkscape.

Or literally any program...

John Rennie

@PrathyushPoduval when you boot off the Win10 install disk or USB key there are two options. The simplest route is to take the Custom option when you're offered the choice of Upgrade or Custom, and that takes you to a screen where you can delete the existing partitions and create new ones.

Transcript for