The h Bar

John Doe

17:00

@EmilioPisanty Starting to look more like what you have after getting ordering right.

Emilio Pisanty

@JohnDoe in which case you're done, right?

John Doe

@EmilioPisanty Yes almost, the numerator is the same now. Is the denominator there to indicate the amount of probability of finding the state in $| + \rangle$ at the start, hence the the fraction $P$ gives the ratio of the probability after to the probabilty at the start of finding the particle in state $| + \rangle$? Hence this is the intensity?

Emilio Pisanty

@JohnDoe yes

though frankly, directly modelling step 1 is pretty silly. Instead what you normally do is you read step 1 as a preparation step giving you $|\psi\rangle = |+\rangle$, and then you start off the manipulations from step 2 onwards.

but since you already had the projectors right I let it stand

John Doe

@EmilioPisanty Okay that makes sense. In you answer it seems that you stating that the intensity does not depend on the intial $| \psi \rangle$ at all if $\psi \neq | - \rangle$?

Slereah

There are 4 libraries with the Tipler thesis

0celouvsky

17:09

@Slereah which ones?

Slereah

If I ask them will they just send me a pdf for free

0celouvsky

is Tipler dead?

Slereah

worldcat.org/title/causality-violation-in-general-relativity/…

0celouvsky

@Slereah yes

@Slereah I can go to the university in MD next time I'm home

college park

Emilio Pisanty

@JohnDoe That is correct. Work it out.

Slereah

17:11

Well we can try that if they won't send it

catalog.umd.edu/F/…

0celouvsky

is it a holy grail of GR papers?

Slereah

There we go

University of Maryland

John Doe

@EmilioPisanty Will do. Thanks a lot for your assistance, it's been quite informative.

Slereah

No, it's just not available online

0celouvsky

@Slereah I can definitely get it because I'm a university student

Emilio Pisanty

17:11

@JohnDoe take care.

0celouvsky

they will send it to me

write the email and I can send it

Slereah

"hello plz send thesis"

It's in the UMCP Severn Library University Archives apparently

status : non-circulating

It's a secret

0celouvsky

wtf

oh, that just means it's not on the shelves

Slereah

yeah probably not

It's probably in some dusty storeroom

0celouvsky

you have to email the math-t.phys person

Kiarash

17:21

I've heard it's not possible to have wave function in 2 dimensions. does anyone know anything about it? is it right?

0celouvsky

@Slereah does $\sqrt{|a|^2+|b|^2}\le |a|+|b|$ look right?

ACuriousMind

@Kiarash What do you mean? What kind of wavefunction?

0celouvsky

never mind

Slereah

@Kiarash what

@0celouvsky Square it baby

0celouvsky

@Slereah yeah

just checking sanity

Slereah

17:25

you can most definately have wavefunctions in two dimensions

Kiarash

quantum mechanical wave function. I heard it relates to the algebraic topological properties of R^2.

@ACuriousMind

ACuriousMind

That makes no sense, what's wrong with wavefunctions in $L^2(\mathbb{R}^2)$?

0celouvsky

algebraic topological properties?

$\Bbb R^n$ is pretty boring from a topological perspective

(algebraic topology)

Slereah

also what does "in two dimensions" mean

ACuriousMind

Also, that. All $\mathbb{R}^n$ are contractible, they don't really have topological properties

Slereah

17:26

Two spatial dimensions or one spatial + one time

Kiarash

@ACuriousMind yup. but R^2-{0} is not contractible. I don't know that much about it. I just heard it and I know it somehow relates to statistical mechanics of identical particles. (just the keywords I've heard!)

@Slereah 2 spatial dimensions

Slereah

Are you talking about anyons

ACuriousMind

@Kiarash There is something special about two dimensions - you not only have bosons and fermions, but anyons

The reason is that while the universal cover of all the higher rotation groups is twofold, in two dimensions its a countably infinite cover

That would indeed be an "algebro-topological property"

Slereah

Then you have the 1+1 dimensional spacetime where the spinors are completely bogus

Kiarash

@ACuriousMind yup! anyons. thank you!

0celouvsky

17:37

What does the universal cover of the plane minus a point look like

I've never thought about it

Maybe just modify the infninite rotini

Slereah

plane minus a point is just a cylinder

0celouvsky

That's not simply connected

Slereah

Just use polar coordinates

Well yes, the cover is $\Bbb R^2$

Take polar coordinates and then make $\theta \in \Bbb R$

0celouvsky

I think my modified infninte rotini is R2 in disguise

Slereah

mama mia

ACuriousMind

17:46

@0celouvsky It's an infinite "spiral"

0celouvsky

@ACuriousMind you mea rotini

ACuriousMind

A helicoid if you want to be fancy

0celouvsky

And I already got it

Looks like an infinite rotini to me.

So once again I was right

ACuriousMind

"The infinite rotini" sounds like the worst magician ever.

2

0celouvsky

@ACuriousMind and yet it's a perfect description of the space

Slereah

18:04

I think pretty much every 2D manifold will have $\Bbb R^2$ as a universal cover

Except the few quotient manifolds of the sphere that aren't also a sphere

Are there any simply connected manifolds in $\Bbb R^n$ that aren't products of $\Bbb R^a$ and $S^b$, $a, b < n$?

Emilio Pisanty

anybody got time and inclination to check up on this?

0

A: Non-linear optics Hamiltonian

Your expression for the hamiltonian is incorrect. Following up the reference trail of the paper you quote quickly leads to a related paper that makes it clear that the relevant quantity in that formalism is $$ H = \frac12\int\left[ \int \mathbf E\cdot \mathrm d\mathbf D\right]\mathrm d\mathbf r, ...

it does look like there's some significant monkey business in that paper

Emilio Pisanty

18:19

oh, sciencealert, you're such a paragon of careful journalism

DanielSank

18:49

@EmilioPisanty What... the...

I don't...

?

@0celouvsky That's amazing.

Emilio Pisanty

19:08

@DanielSank this breathless fanboy of a piece

ultimately not a terrible mistake

but in the context of how terrible the article is, though...

loltospoon

Hello everyone

I have an interesting question

I have to do a final project for an electrodynamics class

And I would like to make it related to my favorite Marvel character, Iron Man

:D

Does anyone have any ideas? The project is a presentation + paper. I need to present on something that is related to the concepts learned in class. The entire class simply follows Introduction to Electrodynamics by David Griffiths.

AccidentalFourierTransform

7

Q: How to make sense of quantum fields differential equations?

A quantum field is an operator valued function, that is, a function $\varphi(x)$ defined on spacetime which assigns operators on a Hilbert space to each event $x$. In a more rigorous approach a quantum field could be defined as an operator valued distribution on spacetime. Anyway, it is quite co...

@Slereah you should post an answer there ^

you know much more than me, you'd get the bounty

0celouvsky

19:26

@DanielSank what is?

skull petrol

@loltospoon how about if Iron Man became magnetized and you could do something on his field lines as he flies around the North Pole?

AccidentalFourierTransform

@loltospoon something related to ACDC?

skull petrol

Don't you need a slash between AC and DC?

Pardon me, "slash" plays for guns and roses :-)

AccidentalFourierTransform

0celouvsky

I don't get it.

skull petrol

19:36

Of course you don't.

AccidentalFourierTransform

Of course.

skull petrol

Trollers gotta troll.

AccidentalFourierTransform

trollers gotta trolle

skull petrol

:D

Nick Irelan

friendly convo i dropped in on lol

AccidentalFourierTransform

19:42

WHO ARE YOU

Nick Irelan

i am nick

AccidentalFourierTransform

hi nick

:: blushes ::

DanielSank

@0celouvsky The thing I replied to.

skull petrol

We like to keep things friendly around here @NickIrelan welcome :-)

loltospoon

@skullpetrol I was thinking of somehow relating something he is known for to a concept in Electricity and Magnetism

Nick Irelan

19:48

Ty, this is my first time here @skullpetrol

loltospoon

For example, I could do a presentation on his heads-up-display (HUD) and talk about the resolution limits of the human eye

But I'd really like to talk about his chest piece (mini arc reactor) but I don't know how to relate it to electricity and magnetism

Nick Irelan

Mini arc reactor? From Iron Man?

skull petrol

I guess I don't know enough about this guy.

Jaime Gallego

@AccidentalFourierTransform github.com/lhartikk/ArnoldC

0celouvsky

@DanielSank on mobile 😰

AccidentalFourierTransform

19:51

what in tarnation

> TALK TO THE HAND "hello world"

0celouvsky

@skullpetrol what the hell?

Are you calling me a troll?

What have I done to you?

AccidentalFourierTransform

@JaimeGallego btw how did your exams go?

skull petrol

You call me an old woman.

>8(

Jaime Gallego

@AccidentalFourierTransform They went quite well. But the rate is going up tremendously. Our Spanish classes are now a unit a day.

0celouvsky

If you're in the business of calling me a troll you bet you are

Nick Irelan

19:54

just be nice. you dont gain anything from arguing on the internet

skull petrol

^

AccidentalFourierTransform

@JaimeGallego damn

high school sucks

0celouvsky

@NickIrelan that's stupid

Jaime Gallego

Plus I have the SAT a month from now

AccidentalFourierTransform

it is worth the effort though

Nick Irelan

19:56

sorry @0celouvsky its the truth though

AccidentalFourierTransform

I hope you get accepted somewhere in the US

good luck with that

skull petrol

Are you in any AP classes? @JaimeGallego

Jaime Gallego

AP does not exist in Spain, at least not in the public education system

skull petrol

:(

Jaime Gallego

I'm on a bit of a disadvantage there, but no prob

0celouvsky

19:57

@NickIrelan the internet is not daisies and sunshine

There are old women like @skullpetrol that are fond of character assassinations

skull petrol

But it can be @0celouvsky

Jaime Gallego

@AccidentalFourierTransform Thanks!

Nick Irelan

@0celouvsky if someone says something about you they want you to respond in turn and be upset though

dont feed into it

yeah the more you get upset the more they will use it against you

0celouvsky

Yep, there's only trolls here

skull petrol

(removed)

I still cannot believe the raiders are moving to Las Vegas.

2

Nick Irelan

20:02

well CA doesnt need more teams

skull petrol

Davis jr is an animal

NY and Florida have 3 teams each.

Nick Irelan

NY only does techically

the jets are from New Jersey

TanMath

Does anyone here know a lot about open quantum systems and the FMO complex? I have some questions on some articles I have read...

skull petrol

Askaway.

0celouvsky

No one knows

TanMath

20:08

you changed your name...

Hey @DanielSank...how's everything @ google going?

1. is quantum dissipation the same as recombination?

0celouvsky

@TanMath what?

TanMath

2. What exactly does thermal relaxation mean? Why is it that the Redfield equation includes it, but Lindblad doesn't? I know it has something to do with the so-called secular approximation...

@0celouvsky used to be 0celo7

skull petrol

He changes his name every other day 0celo7, 0celou, and 0celouvsky

TanMath

3. So, there is dephasing, recombination, relaxation, trapping... what other effects can the environment have on the FMO complex?

0celouvsky

My name has been Revolver J 0celouvsky since as long as I remember

TanMath

20:12

been reading this:

arxiv.org/abs/1311.4688

skull petrol

What's the J stand for?

TanMath

and this:

arxiv.org/abs/0807.0929

Of course, the latter model only includes dephasing, trapping and recombination, using the haken-strobl model...

The former model includes the quantum dissipation and relaxation

Nick Irelan

I notice tanmath is the only one talking about his questions

TanMath

lol

0celouvsky

@skullpetrol Joliqué

@NickIrelan what does that mean?

Nick Irelan

20:15

I mean someone should answer him

TanMath

nobody here knows open quantum systems... except @DanielSank... and @MarkMitchison

0celouvsky

@NickIrelan no one here knows how to answer them and there's no duty to answer questions regardless

We're not going to stop the regularly scheduled conversation because @TanMath asked @DanielSank a question.

TanMath

@0celouvsky "asked anybody who knows open quantum systems"

just saying...

0celouvsky

Which is probably only DS, let's be real.

TanMath

true...

does MM come here anymore?

0celouvsky

20:20

No

skull petrol

^

TanMath

aw... that's really sad...

He is also an expert in that field... especially since his former advisor used to work in the same exact field of quantum biology in photosynthesis (FMO complex)!

:36371837 what's this leadership you are talking about?

skull petrol

(removed)

TanMath

??

@0celouvsky why the delete?

0celouvsky

Because they are watching.

TanMath

20:23

??

is this 1984??

skull petrol

Big brother is watching.

TanMath

lol

where is big brother?

Nick Irelan

I feel like i need to start deleting stuff

TanMath

@bigbrother where are you?

Nick Irelan

/nick Big Brother

skull petrol

20:26

:-O

Physics Meta

0

Q: How to get the Bronze Editor Badge

I was trying to get the Bronze Editor badge, so I edited one post by fixing a few grammar errors and making the question clearer. However, I thought editing was a privilege only earned at 2000 rep? After I submitted my edit, I got a message saying it would only be displayed once peer reviewed. ...

support editing badges

0celouvsky

@NickIrelan this isn't IRC

TanMath

Big Brother, show your face if you dare!

skull petrol

>8(

Nick Irelan

honsetly this is better than irc

TanMath

20:27

see...nothings happening...

Nick Irelan

its like a discord/irc mix

0celouvsky

@NickIrelan no, the white knighting is awful

TanMath

big brother doesn't exist...

who made you think he exists?

0celouvsky

The flag system is completely broken

TanMath

so complain to the mods...

problem fixed!

Nick Irelan

20:30

we just need bots for trivia and such

skull petrol

trivia

Noun: trivia (countable and uncountable, plural trivia)

insignificant trifles of little importance, especially items of unimportant information
These trivia take up too much of the day.
This trivia takes up too much of the day.
A quiz game that involves obscure facts.
I joined the trivia club this semester!

(8 more not shown…)

Adjective: trivia

nominative feminine singular of trivius
nominative neuter plural of trivius
accusative neuter plural of trivius
vocative feminine singular of trivius
vocative neuter plural of trivius

(2 more not shown…)

Nirelan

have you ever been on IRC

skull petrol

yes

Nirelan

well check out a triva room on it

skull petrol

Will do.

Jaime Gallego

20:36

Ingsoc is doubleplusgood

We have always been at war with Eastasia

0celouvsky

@TanMath he told me

@TanMath they can't do anything about it

it's a stack exchange wide policy

the SE staff don't care either

Nirelan

lets all move to discord

skull petrol

The system is what it is.

TanMath

@0celouvsky complain to the SE staff until they get so annoyed that they will be relieved of your constant complaining when they fix it...

Nirelan

or relieved when they ban you

skull petrol

20:43

been there done that^

ban

Verb: ban (third-person singular simple present bans, present participle banning, simple past and past participle banned)

(transitive, obsolete) To summon; to call out.
(transitive) To anathematize; to pronounce an ecclesiastical curse upon; to place under a ban.
(transitive) To curse; to execrate.
(Can we find and add a quotation of Spenser to this entry?)
(Can we find and add a quotation of Sir Walter Scott to this entry?)

(15 more not shown…)

Noun: ban (plural bans)

prohibition
Milton
under ban to touch
A public proclamation or edict; a summons by public proclamation. Chiefly, in early use, a summons to arms.
Bans is common and ordinary amongst the Feudists, and signifies a proclamation, or any public notice.

(56 more not shown…)

Physics Meta

21:36

0

Q: Bounty going to waste - what should I do?

I recently put a bounty on a question, but still no one is answering it. When the bounty period ends, will the bounty just go to waste? If no one is answering I would prefer to just answer the question myself and get my 50 rep back, but I don't know if this is possible or allowed. Any advice w...

support questions bounty

0celouvsky

22:44

hello?

heather

hello

ACuriousMind

Hello.

heather

new meta post I made - anyone want to comment?

0

Q: Let's get things rolling again with the homework policy

Okay, so the last time we had a focused discussion of the homework policy was August 2016. Blech. Then, we got on a bit of a tangent which was partly my fault. And now here we are, still stuck in the same spot. I don't know about you, but this homework policy needs to be fixed, and before anyone...

discussion homework

ACuriousMind

Still catching up with my inbox, have patience

heather

23:00

okay

ACuriousMind

@heather 1. I don't like the middle part, in particular its focus on individual users and that it comes before you tell us what you actually want to do. I'm halfway through the post and I know that DanielSank has had some great idea that ACuriousMind approved of, but you haven't told me what it actually is ;) Put the important information up front and the fluff later.

2. It's not exactly clear to me what the post is asking for. Where I last left off with Daniel was that we wanted to pose a meta post that would list all the bits and pieces of phrasing that need to be changed, and the answers would be specific proposals for specific wording of these pieces. It's not clear to me whether your post is asking users to vote on Daniel's old formulation or asking them to propose something new

3. The overview over what exactly we need to change/reword is missing.

heather

#1 I just fixed

#2, I was originally thinking that I was asking for users to vote, but now that you say it, I guess the latter is probably better

#3, could you clarify what you mean?

ACuriousMind

@heather There are six different pieces of text relating to the homework policy that each need to be formulated. An overview is in the old thread about the homework policy

loltospoon

@Nirelan yea. I'm trying to make an electrodynamics presentation explaining one of the concepts from our class via the Iron Man suit

ACuriousMind

That is, the things you quote in the question are a first step, but we can't just say "great, lets take that wording and stick it into the policy" because it doesn't cover everything that needs to be changed.

heather

23:14

right, okay.

ACuriousMind

So right now it's a post that tells us we should do something about the homework policy but it doesn't really tell us what exactly. This is why Daniel wanted to crowdsource the new meta post before it going live, by the way - I'm not sure why that thing just fell on the wayside again, but these meta posts need to be carefully crafted

heather

okay, how's the edit?

ACuriousMind

Much clearer on what input is being sought, very good

Physics Meta

0

Q: Let's get things rolling again with the homework policy

Okay, so the last time we had a focused discussion of the homework policy was August 2016. Blech. Then, we got on a bit of a tangent which was partly my fault. And now here we are, still stuck in the same spot. I don't know about you, but this homework policy needs to be fixed, and before anyone...

discussion homework

ACuriousMind

I'm a bit unhappy with the giant and a bit borked block quote in the middle - if we're sourcing new proposals you shouldn't quote the old - and incomplete - one in the question

heather

23:19

okay

let me fix that then.

ACuriousMind

I also would tone down the amount of fluff about how tiring it is to talk about the policy, but since it's your post it can be as grumpy as you like :P

heather

=P

how is it now?

ACuriousMind

Much better than what we started with :)

heather

=D

I'll reduce the fluff a bit, and that should round it out nicely.

okay, how's the fluff sector now?

ACuriousMind

Now the main problem is to get someone to actually sit down and craft these texts. Emilio posted a complete set of proposals with the older question, and as far as I can see no one ever edited any of these proposals. We basically implemented what Emilio single-handedly proposed.

@heather Now it's a fine question, I'd say.

heather

23:25

@ACuriousMind okay, thank you for your help!

@ACuriousMind I might try to work on them, and @DanielSank probably will.

vzn

@heather hey any interest in collatz still? this new numberphile video seems to be getting a lot of views & maybe generating some recent burst of internet focus on the problem... :)

Collatz Conjecture in Color - Numberphile

►

heather

what are your thoughts on "the problem solving policy" being our temporary new name for it @ACuriousMind

ACuriousMind

@heather Everyone comes here with a problem they want solved, I think it's not a good name and would much prefer something like "our policy for calculation requests", but less unwieldy.

heather

"arbitrary calculation policy"?

0celouvsky

Hello

heather

23:30

@0celouvsky hello

ACuriousMind

@heather I'm not sure what the "arbitrary" is supposed to mean there, and I think "calculation policy" just sounds weird...

heather

everything i'm thinking of is stupid or unwieldy =/

brb

0celouvsky

@ACuriousMind This book on operator theory says "the definition of a manifold is explained in [H63]." Now, I know the usual references for such things, and H is not one of them. So I look in the back and it's Hörmander's "Linear Partial Differential Differential Operators"

ACuriousMind

@heather I have the exact same problem

0celouvsky

You know you're in deep trouble when a book references a PDE book for manifold theory :D

ACuriousMind

23:33

Very strange indeed

0celouvsky

@heather I can ask a conceptual question that is off-topic, no?

Like a multiple choice question that involves no calculation

Is that supposed to be off topic?

heather

okay, back

@0celouvsky yeah, that's off-topic

you're right, it's not just "no calculation"

0celouvsky

so it's not a calculation request

heather

it's "nothing without showing your work"

0celouvsky

I conclude that we should just delete the whole site imo

heather

23:41

um.

0celouvsky

leave the chat

but give me mod powers

heather

the "show your work" policy?

@ACuriousMind

not really short enough though

ACuriousMind

@heather We're not making new policy. The highly upvoted post by Daniel that you cite as justification for moving forward is definitely about the calculation-y aspect of questions

Insufficient effort is a different - and in no way less difficult - debate.

heather

urgh, good point

ACuriousMind

Also, we don't need to cover strange edge cases - how many of these multiple choice homework-y questions are there that the calculation-y policy would not cover? One a week? Custom close reason "We don't do your homework for you" is fully sufficient for that

0celouvsky

23:46

@ACuriousMind With an attitude like that I'll ask a bunch just to prove you wrong.

@Danu hola

heather

that's the thing though @ACuriousMind - we shouldn't be using anything related to "homework" as a close reason.

this renaming should cover everything the homework policy did.

Danu

@ACuriousMind did you see this? arxiv.org/abs/1703.09238

ACuriousMind

@heather The first close voter will use whatever custom close reason they want.

Danu

The abstract sounds like it may in passing address your recent question

0celouvsky

what's a T-brane?

heather

23:49

@ACuriousMind i mean that we shouldn't rely on custom close reasons involving the word "homework" for edge cases.

ACuriousMind

@heather I 100% guarantee you that any reformulation we come up wtih will slightly change what exactly it applies to when read literally

Danu

We all are, my child

ACuriousMind

Literally, any change in phrasing will some nitpicker point out that a question of a very specific type is not covered anymore

Danu

@0celouvsky ^^

ACuriousMind

And it's pointless anyway because we're currently not following the letter of the old policy!

0celouvsky

23:50

@Danu ...mammals?

heather

but one a week is a not insignificant edge case.

ACuriousMind

@Danu I asked the question precisely because I don't want to hunt through the literature myself :P

@heather We close over 250 questions a week. It is.

0celouvsky

@DanielSank For some reason the analysis/operator algebra seminar was invaded by a stochastics person today. I didn't understand much...

Danu

@ACuriousMind SORRY FOR HELPING ;)

heather

@ACuriousMind alright then.

ACuriousMind

23:54

Well, I mean, I made taht "one a week" up. But you really have to keep in mind that we close around 100 posts per week for being homework. Losing coverage for one or two is still morally a "rewording" in my book

People wanted to do this rewording because "don't let perfect be the enemy of good" so let's keep at that.

heather

okay.

::suppresses OCD tendencies::

how about the "conceptual question policy"?

Transcript for