The h Bar

Cows

00:10

@user929304 still there?

user929304

Sure

Cows

Awesome

enumaris

3 hours to go through 1 epoch of 1.2million training examples :D :D

not too bad

Cows

so first some background. I recently appreciated this $\Psi(x,t) = \Sigma_n a_n\psi_n(x)e^{iE_nt}$

I am attempting to understand QM

user929304

So far so good :)

Cows

00:14

ok so want to understand averages now

let me explain

What is an average value?

of $\psi$

and what is a time average, of $\psi$?

Is this terminology even used?

ACuriousMind

No, because it's underspecified. You don't take expectation values of wavefunctions, you take expectation values of observables with respect to certain states/wavefunctions

Cows

so like $<\psi | A | \psi>$

user929304

Indeed, the psi s are just complex vectors in Hilbert space, you can add them or compare their overlaps

Cows

This is the average value of A with respect to psi

so given

user929304

In your example, A is an operator not a vector, and an operator indeed has an average

As each eigenvalue has a probability associated to it, so you can meaningfully define an average value for it

enumaris

00:19

For the general wave function $\Psi(x,t)$ you will get expectation values of operators in this manner: $\langle A(t)\rangle = \int_{-\infty}^{\infty}\Psi^*(x,t)A\Psi(x,t) dx$

Cows

$A_{t_0}$ and $A_{t_{1}}$ is there an appropriate terminology for time average between the two?

enumaris

You can plug in the expanded version

if u wish

ACuriousMind

@Cows What do you mean by $A_{t_0}$? Don't throw around undefined notation

Cows

let me attempt to define

enumaris

I should have used the notation $\langle A \rangle (t)$ for clarity

the expectation value of $A$ will be generally time dependent if the wave function is itself time dependent

Cows

00:21

I mean a relation between an operator $A_0$ defined at time $t_0$ and one $A_1$ defined at time $t_1$

user929304

@Cows you can define operators in time, you just have to move to Heisenberg picture, but you don't need to if you only want to look at expectation values

ACuriousMind

@Cows If you have operators that are defined at certain times, then you are in the Heisenberg picture and your $\psi(x,t)$ shouldn't depend on $t$. I mean, there are explicitly time-dependent observables but they're rare and not really of interest right now when you're starting QM

Cows

aha hmm interesting

enumaris

Maybe he's doing time-dependent perturbation theory where both have a t dependence? o.o

See: en.wikipedia.org/wiki/Interaction_picture

but probably don't skip to that when you're just starting QM...

Cows

ok

good night

00:27

@Cows allow me to introduce you to @SirCumference

he loves mayo too. he dips his electronics in it every night.

Cows

@goodnight hehe

enumaris

ew

good night

Nov 25 at 6:43, by Sir Cumference

Wow...I dropped my charger plug into a jar of mayonaise

dip drop same thing

quartata

User with a bunch of R/A posts: physics.stackexchange.com/users/176849/boi

ACuriousMind

@quartata Already on it ;)

good night

00:32

@ACuriousMind f a s t b o y e

quartata

Thanks

ACuriousMind

@goodnight ?

quartata

Memes

good night

@quartata idk what you're talking about

:p

enumaris

I reread Ballentine chapter 1 yesterday...the spectral theorem and rigged Hilbert spaces finally clicked lol

learning is weird

good night

00:44

how do you find friends irl

Phonon

@ACuriousMind speaking of steam by the way, do you play anything these days? Have you checked out The Witness yet?

enumaris

go out and meet people

how else do u find friends irl

good night

@enumaris how

that's too random

anything new in the physics literature in the past year?

any new qft or gr books?

that matter

enumaris

01:26

I'm rereading a bunch of old books heh

good night

lmao

david tong flipping the generic math in physics talk

►

enumaris

hmm

user929304

@ACuriousMind by the way, do you have posts where you explain a bit the problem with position/momentum eigenstates not being proper states in H, and the need to extend H to include them? I recall having read one very clearly explained one from you, but I cannot find it anymore... :(

DanielSank

01:55

What's going on in here?

Physics?

Phase

02:18

@goodnight enumeris is right, to meet people irl you gotta... meet people irl

The Dark Side

02:40

@JohnRennie With all due respect, I don't think that argument holds. The vectors are not anti-parallel, only their z-projections annul each other. So, the argument is $M_L = 0$ for sure. I think the question stands, why $L = 0$?

Mohammad Areeb Siddiqui

-2

Q: Working out equation of motion from potential energy

A potential energy of a particle in 2 dimensions $x$ and $y$ is given by $$V = \dfrac{k(x^2+y^2)}{2}$$ And the equations of motions for this particle are to be calculated given that the mass of the particle is $m$. I used $F_x = -dV/dx$ and $F_y = -dV/dy$ and got \begin{align} m\ddot x =& -kx ...

anyone?

The Dark Side

@JohnRennie - By virtue of "spatial quantization", there is always an angle $\theta$ between ${\vec L}$ of any of those electrons and ${\hat z}$, such that $\cos \theta = \frac{m_l}{\sqrt(l(l+1))}$. How do you conclude that the vectors annul each other?

Cows

Just got back from buying some very expensive water. Watching Tax reform debate now

Semiclassical

03:05

let me know if graduate student tuition waivers get mentioned

i'd want to watch that

Semiclassical

03:18

@Cows I meant to ping you on my last message, woops

Cows

03:32

Yup they got mentioned several times.

Hmm presumable grad students make between 10 and 15k a year

Correction if you go to a top 10 uni Then you get between 35k to 60 k in graduate school.

i.e 35k to 60k a year

Semiclassical

huh, so it is getting mentioned? good

which debate is this? the cnn one?

Cows

Well 35k a year hehe

I had no idea stanford grad students could make as much as 45k lol. That's.quite a bit of cashola lolz

Semiclassical

is that their stipend or their tuition waiver?

Cows

I think their salary ? May be

google.com/…

I happen to know drom talking to some people that you can hit 70k if you play the game right

Sorry was Charing from phone. Using my kindle now

0celo7

03:52

who the hell is getting a 60k stipend

maybe if you get an NSF fellowship and a department stipend

Semiclassical

yeah, that doesn't sound right

The Dark Side

It could be 60 k of millicurrency !!

0celo7

60k Canadian (shots fired)

Cows

I.e 70k if you get other things too, but I won't really know I am not a grad student. Especially not a Stanford grad student to everyone's delight I might add.

Semiclassical

huh: phdstipends.com

0celo7

03:56

@Semiclassical Fuck, can I just be a PhD student at Northwestern forever?

Or is that over 5 years

Cows

@0celo7what do younger there?

0celo7

that makes zero sense

Cows

Just in case anyone was wondering I have never been a graduate student nor have I been at any point lol. He he

Sorry was typing while eating

Semiclassical

What I wince at are the stipends which work out to be significantly less than what a living wage would be for the costs in that area

The Dark Side

^

They are, mostly !

Cows

03:59

Wanted to ask how long you were there for

Semiclassical

i'm looking at some of the stipends listed for the UMN, and while the STEM ones are pretty much at living wage level

one in American Studies works out to 0.70 living wage (whatever that means, you'd have to look into the guts of that)

which...yikes

Cows

Yeah

Semiclassical

oof: there's a "department of design, housing, and apparel" one which is at 0.47

Cows

If you do literature you are screwed

Semiclassical

this is all self-reported, though

and I could well believe there's some details missing

Cows

04:04

USC math seems to be ~15k

There is a strong correlation between money and talent pool at all levels

@Semiclassical don't worry the Republican guy said it won't go anywhere during the debate

So nothing is likely to change on this front

Semiclassical

we'll see.

Cows

Unless he lied hehe

Semiclassical

he's one person.

even if he doesn't think the language shouldn't be there, that doesn't mean others won't.

as long as the house bill is out there with that language in there, I'm not going to rest entirely easy.

Cows

That's true

Semiclassical

though I'll feel better if the Senate bill comes out and it's not in there

Cows

04:14

If your PhD is on a topic marginally close to engineering I am sure you PI can come up with creative ways of subsidizing the difference

North Korea just showed the world they are on the nuclear table too

Anyways off to study to an upcoming interview. Gotta make money. . . .

Anonymous

04:57

4h-

Anonymous

Oops, typed by mistake. Ignore ^

0celo7

05:12

@Cows do you think engineering professors have random money out the ass?

Cows

@0celo7 lol, most of the engineering professors I have met are also running companies on the side. I knew(slaved for) one who did. Unfortunately i was too naive and illequiped to take advantage of any profits lol

0celo7

I don't know a single one who does that. Where'd you go, Harvard? Princeton?

Cows

by running companies I mean pushing out patents and getting funds from other sources for innovation et al

ha Harvard/princeton moi? lol

Non pas du tout

J'etait eleve a ASU

@0celo7 you are french right?

0celo7

No. Why would you think that?

Cows

oh I assumed sorry

lol

but yeah no I was an undergrad at ASU some years back

I did not graduate though hehe

At any rate a lot of Physics profs were moonlighting as engineers( engineering research guy/gals?)

enumaris

05:27

time to learn RNNs woooo

Cows

although CS is the only guaranteed way to get moola

no other way

enumaris

I want moola

Cows

Moola is great

people treat me like a human when i have it and as a dog when I have no moola

I used to be a dog

but thanks to moola I am human too now

@enumaris you will have no problem getting moola. Your background is good

enumaris

hopefully XD

Cows

hehe going over php interview questions and answers

@0celo7 poincare was an engineer right?

0celo7

05:39

dunno

Cows

mining engineer to be precise

but his phd was in differential equations

John Rennie

@Blue we can do the install whenever you're ready

Anonymous

@JohnRennie I'm ready!

Anonymous

We can do it now

0celo7

What are you doing

installing malware?

Anonymous

05:45

@0celo7 Ya...

Anonymous

Basically changing from 32-bit to 64-bit

Cows

via vnc or teamviewer?

or voodooo ? lol

John Rennie

The first step is to prep the USB key

Anonymous

Okay, how to proceed?

John Rennie

Put the USB key into the laptop then open a command prompt

Anonymous

05:49

@JohnRennie Done

John Rennie

Type diskpart

When you get the doskpart> prompt type list disk

Anonymous

Anonymous

done

John Rennie

Cool. Disk 0 is the hard disk and disk 1 is the USB. Type select disk 1 then list partition

That should show a single partition 14GB in size

Anonymous

05:53

ok

enumaris

Bernardo made me promise to not use proprietary malware

John Rennie

Now type clean

This will completely wipe the USB key

And once that's done enter these four commands:

Anonymous

@JohnRennie Uh, but doesn't the USB have the Windows files? That will get deleted too, right?

John Rennie

create partition primary
select partition 1
active
format fs=fat32 quick

@Blue you are going to copy the Windows install files from the ISO to the key

Anonymous

Actually I had already copied those files yesterday. But there are some other files on the USB key too. So, okay, I'm following the steps: 1) clean ...

Anonymous

05:58

"DiskPart succeeded in cleaning the disk."

John Rennie

You can copy and paste the next four commands into the commnd prompt

Saves typing ...

Anonymous

@JohnRennie Yeah, that's what I did :P

Anonymous

"0 percent completed"

John Rennie

OK, once the format command has finished type exit to exit Diskpart then close the command prompt.

Anonymous

06:00

" 100 percent completed

DiskPart successfully formatted the volume."

John Rennie

Now eject the key and reinsert it. You need to do this because in cleaning it we removed the drive letter for the key

Anonymous

@JohnRennie Okay, done

Anonymous

@JohnRennie Done

John Rennie

Now mount the ISO

Anonymous

@JohnRennie You mean copy the ISO to USB? Or something else?

John Rennie

06:03

Open a Explorer Window and navigate to wherever you downloaded the ISO file

Right click on the ISO file and choose the option Mount

It will create a new virtual DVD (with a new drive letter)

Anonymous

This is what I get when I click Mount

John Rennie

Now you need to copy all the files off the virtual DVD onto the key. I would do this using a command prompt and the xcopy command, but you can do it any way you want.

The copy will take a while ...

Anonymous

I just did Ctrl A+Ctrl C+Ctrl V :)

Bernardo Meurer

@JohnRennie Morning John!

Anonymous

06:06

Yeah, 5% now

Anonymous

Hi, Bernardo

Bernardo Meurer

@Blue Have you heard the word of our lord and savior Richard Stallman?

John Rennie

@BernardoMeurer oh no! Bernardo's here to see us installing ... WINDOWS!

Anonymous

We are installing proprietary malware so that we can install free software later on (linux) :P

Bernardo Meurer

@JohnRennie ::prepares exorcism equipment::

enumaris

06:07

lol

Bernardo Meurer

@JohnRennie NOT ON MY CHRISTIAN CHAT

John Rennie

@BernardoMeurer to be far Blue is only doing this so he can use the Linux subsystem - that's the good news.

Bernardo Meurer

@JohnRennie Ugh, I despise the LSW :P

John Rennie

The bad news is that the Linux subsystem is ... dum, dum DUUUUUM ... Ubuntu! :-)

Bernardo Meurer

@Blue Why not dual boot?

@JohnRennie There are other distros! He can use SUSE

John Rennie

06:09

Not supported in the Windows 10 Linux subsystem

Bernardo Meurer

SUSE isn't as bad, I have Arch on LSW on my Windows back in BR

What?

Anonymous

@BernardoMeurer My PC has 32-bit Windows. That's why I'm trying to install 64-bit Windows first. Only the 64-bit supports dual boot

Bernardo Meurer

I had it back at home .-.

Anonymous

My processor is x64

Bernardo Meurer

@Blue Hum, that's not true, I am certain of it.

You'd just need to dual boot i686 Linux :)

I think

Anonymous

06:10

Yeah, but I think the 32-bit has some issues anyway. I can't use Matlab for example...

Anonymous

Better to use 64-bit

John Rennie

@Blue have you copied anything you want to keep off the hard disk? The reinstall will completely wipe the hard disk.

Anonymous

@JohnRennie I don't have anything important on the hard disk. Just pdfs downloaded from libgen :P I can get them again

Bernardo Meurer

@Blue Definitely don't use i686

Anonymous

And mostly I have everything backed up on Google Drive

John Rennie

06:14

Cool :-)

Anonymous

76% percent now

John Rennie

I like to do a comparison of the USB and the ISO to confirm everything copied. I do this using a command line tool of my own devising. Do you want to grab a copy off my web site?

Anonymous

@JohnRennie Okay, sure

John Rennie

swarchive.ratsauce.co.uk/dircomp.exe

Save the file in some convenient directory that you can find ina command prompt

Anonymous

Saved it on Desktop. .exe format

Bernardo Meurer

06:17

@JohnRennie Just use rufus?

John Rennie

@Blue Open a command prompt and type cd Desktop

Anonymous

done

John Rennie

type dircomp -? and you should get info about the command. This is just to check it downloaded safely.

0celo7

Ubuntu can’t connect to the internet

Anonymous

John Rennie

06:20

Excellent :-)

Anonymous

next?

Anonymous

The files have transferred

Anonymous

:)

Anonymous

to USB

John Rennie

Is E: the key letter and F: the virtual DVD letter?

Anonymous

06:21

USB Drive is G

John Rennie

Ok in that case type `dircomp -d -v0 F:\ G:\`

Anonymous

"Comparing "F:\" with "G:""

John Rennie

This will take a while but it it will confirm that everything has copied correctly to the USB key. I'm always extra cautious about this because when the install starts we'll be wiping the disk and there's no way back once we've done that! :-)

Anonymous

Yep! I'll tell you when it's done

Anonymous

Lol...this does take lot of time

Anonymous

06:27

It's still showing comparing :D

John Rennie

To be fair it's comparing 3.5GB of data off a USB2 drive. That's going to take a while :-)

Anonymous

phew phew :P

Anonymous

@JohnRennie So, it's seems all files were transferred properly

John Rennie

OK. We're all set.

You need to restart the computer, then when the Dell Logo appears press F12 a few times until you get a message at the top right of the screen saying Preparing boot menu or something like that

Anonymous

06:35

Alright, let me bring my phone so that I can be online here, meanwhile...

Anonymous

1 min..

Anonymous

Alright. I'm on phone now. Restarting laptop...

Anonymous

@JohnRennie

John Rennie

Hmm, your laptop has UEFI enabled ...

Try the third option down "USB Storage Device"

Anonymous

06:42

Alrighty...

John Rennie

When the installer starts you need to press shift-F10. This will open a command prompt. Then we'll be running diskpart again to clean the hard disk.

Anonymous

Bernardo Meurer

@JohnRennie zdnet.com/article/how-to-run-opensuse-linux-on-windows-10

?

Anonymous

It's showing a setup window

John Rennie

Excellent. Press shift-F10 then type diskpart

Bernardo Meurer

06:44

Wait, wrong link

fossbytes.com/opensuse-linux-on-windows-10

John Rennie

@BernardoMeurer Ah. Cool. I live and learn :-)

@Blue how's it going?

Anonymous

@JohnRennie Done that. It's showing DISKPART>

John Rennie

select disk 0
list part

Bernardo Meurer

@JohnRennie Why are you making him do this?

Why not use the Windows GUI?

John Rennie

@BernardoMeurer I want the disk shiny clean before the install starts

Bernardo Meurer

06:48

Ah, alrighty

John Rennie

I do this a lot. Trust me! :-)

Anonymous

Done. It's showing 4 partitions

Bernardo Meurer

@Blue Yeah, trust the antichrist

Anonymous

And their sizes

Bernardo Meurer

He knows how to set up the malware

:P

John Rennie

06:50

@Blue 450MB, 99MB, 16MB and 149GB?

Anonymous

1- 100 MB 2-77 GB 3- 450 MB 4- 70 GB

Anonymous

3 is the Recovery

John Rennie

Ah, good, that's fine. Now type clean to TOTALLY WIPE THE DISK OH MY GOD THERE IS NO WAY BACK FROM THIS :-)

@Kaumudi.H Hi, remember doing this on your laptop?

user228700

:-) Yep!

Anonymous

Diskpart succeeded!

Anonymous

06:53

Now ? :D

John Rennie

type exit then exit again to close the command prompt. Now we can begin!

Anonymous

Done

Anonymous

Back to setup menu

John Rennie

On the first screen choose whatever language options you want. It will be defaulted to the UK because it's my setup image. Then click Next.

Anonymous

Should I choose US English or UK English. I'm in a dilemma ;)

John Rennie

06:55

Is your keyboard US or UK?

Is shift-3 a dollar or pound sign?

Anonymous

$ sign

Bernardo Meurer

£

The mark of Rennie

John Rennie

Then choose US otherwise the keyboard map will be wrong.

@BernardoMeurer me and the other 60 million residents of the UK :-)

Bernardo Meurer

I meant because the people you give laptops to get shift-3 to be £ :P

John Rennie

Ah, yes :-)

The keyboard is easily swappable if you want to do it ...

Anonymous

06:58

Alright. Language -UK and Keyboard input -US international :)

Anonymous

Click on next ?

John Rennie

Once you've set the regional options click Next then Install now

Then accept the licence agreement

Then choose the lower option Custom: Install Windows only

Anonymous

It's asking me to select which OS to install

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