00:00 - 17:0017:00 - 00:00

Anonymous
5:05 PM
@ııııııııııııııııııııııı The effective mass concept doesn't explain the splitting...

@heather Does this answer not have what you need? It explicitly states that the BBO crystal will have one optical axis $V$ and will convert photons polarized along it into two photons polarized along $H$ orthogonal to that, while it leaves the polarization along $H$ alone.
As far as I have understood what you are looking for, this seems to be precisely the information you wanted.

Sorry if this is a stupid question but is $\langle A\mid=A_i$ and $\mid A\rangle=A^i$?

Anonymous
@CooperCape What does $A_i$ and $A^i$ mean?

Einstein notation thingy

@CooperCape Whenever you find yourself tempted to write an equation that has not exactly the same free indices on both sides, you know something has gone wrong.
An equation of the form $X = Y^i$ is always false, as is e.g. $X^i = Y_{ij}$, because there's an $i$ ($j$) on the r.h.s. that's not there on the l.h.s.

5:18 PM
But like $\langle A\mid=\begin{bmatrix}A_1&A_2&A_3\end{bmatrix}$ right?
So isn't that the same as a subscript index?

If you have a vector $v$ that has components $\begin{pmatrix}v^1\\ v^2 \\ v^3\end{pmatrix}$ in some basis with basis vectors $e_i$, then $v = v^i e_i$.

I know that I'm just wondering if $\angle\mid$ is equivalent to using indices in some cases?

@CooperCape No. $\lvert \cdot \rangle$ is basically just another way to denote a vector, like putting arrows on top as in $\vec{v}$.

Oh I see
And $\mid\rangle$ is the covector or something?

Anonymous
@CooperCape It's the transpose

5:23 PM
Ohhh

Anonymous
Look up bra-ket notation if you wish

This work for higher order tensors than first or...?

@ııııııııııııııııııııııı I tend to agree that it doesn't
but there's relatively little that I can do about that
> If you do not award your bounty within 7 days (plus the grace period), the highest voted answer created after the bounty started with a minimum score of 2 will be awarded half the bounty amount (or the full amount, if the answer is also accepted). If two or more eligible answers have the same score (their scores are tied), the oldest answer is chosen. If there's no answer meeting those criteria, no bounty is awarded to anyone.
In its present form (i.e. unless that answer is substantially improved), I'm unlikely to award it manually
the system will then behave as above

@CooperCape not particularly well, tbh.
I mean, it can handle them, but it the notation will tend to hide a bunch of stuff you might care about
so e.g. $|a\rangle = |b\rangle \otimes |c\rangle$ is perfectly valid in that notation

braket notation sucks dude

5:33 PM
where the LHS is a rank-two tensor, set in the RHS to the tensor product of two vectors
and where of course the rank-two tensor is also a vector because it belongs in a vector space
@BalarkaSen ¯\ _(ツ)_/¯

@ACuriousMind let me take a look - thanks for the reference, though.

it's the worst possible notation except for all the other alternatives

who in their right mind would simultaneously work with row and column vectors

@ACuriousMind that's.... a bit of a simplified picture of nonlinear optical processes

@Blue Welllll. Technically, it is also a covector.
Every vector corresponds to the covector obtained by dotting/taking inner product with it.

5:39 PM
@EmilioPisanty Yeah... This

@Mithrandir24601 have you got any recommendations for intro NLO books?

@EmilioPisanty Erm... It's not introductory, but I've ordered Boyd's Non-Linear Optics textbook...

@Mithrandir24601 yeah, I've had a dig at it, it's OK if you already know the layout of the material, but it's pretty dense

Anonymous
@BalarkaSen Learnt something new today :)

any experience with it?

5:43 PM
@EmilioPisanty Never heard of it...
Not that that's saying much

i found a pdf of boyd on the internet earlier, which is what i'm looking at
it is also what made me figuratively bang my head against the wall, so =P

IT got wise to my shenanigans =(
there I was looking for a book to recommend to @heather

heh

@heather you know what that site is, right?

libgen
the place of free books and shiny things
i try to avoid it, but i already use sci-hub, so.
anyway, i generally find pdfs even off libgen for most books.

5:57 PM
good.

1

I recently encountered a question about "1000 people whispering" and wrote an answer. Subsequently I did some experiments where I recorded a whispered sentence 19 times, and did some manipulations to show how this makes the "inaudible" audible. I would like to update my answer with this work - b...

6:26 PM
@Blue Yes; for that, you need to solve the eigenvalue problem and find the electronic band structure (or at least analyze it qualitatively). The effective mass concept explains the names given to those points of the band (light, heavy, etc.)

Anonymous
@ııııııııııııııııııııııı Which eigenvalue problem? I can't understand why along a single axis there can be two different types of holes

Anonymous
I know E-k differs for different axes

Anonymous
But for the same axis...I can't understand why

Anonymous
Probably something to do with angular momentum and spin momentum

@heather from my experience, the nonlinear part of various topics/courses have two faces depending on your stance: a rather easy one and a very hard one
1st: a rather easy one when thought as part of a course and you're just studying for the exam; because there's not much that can be done other than understanding and reproducing the existing formulas. New questions will be so difficult that are unlikely to be on the exam.
2nd: a very hard and challenging face when you're trying to do research/something new about them because, again, there's not much you can do :)
@Blue I don't know the exact problem, but that plot seems to be a band structure of some crystal. When you solve the Schrodinger equation for the crystal you obtain the band structure, and each band is labeled by a couple of quantum numbers (energy, ...)

Anonymous
6:47 PM
@ııııııııııııııııııııııı These are very hazy for me, still :/

Anonymous
Anyway, thanks

From the preface:
{proudly available on libgen (▀ ͜͞ʖ▀) }

@EmilioPisanty I know but it is my impression that @heather doesn't really care about the correct non-linear optics description so much but rather about a working description of what the spdc crystal does to the polarization in an optical circuit.

@BalarkaSen false

ur false
I was joking; I am not familiar with that notation beyond what it is

7:02 PM
@BalarkaSen hehehe

@DanielSank i am trying to print the fibonacci serie. I created the algorithm to add a number to the one before but i do not know how to repeat this for a given integer "n"

Anonymous
@nasil $t_n=t_{n-1}+t_{n-2}$. Recursion.

@Blue i meant python

Anonymous
@nasil I suppose you can implement algorithms in any programming language

Has Daniel helped you before with this or why did you ping him with that?

7:14 PM
@ACuriousMind yes
@
he helped me before
@Blue i am asking how to repeat a process

Anonymous

@nasil Okay, just making sure you're not pinging random people ;)

@ACuriousMind no problem

@ACuriousMind Stepan Trofimovich Verkhovensky was quite famous for his avant garde orchestral play consisting of poetry uttered forth by inanimate objects. By the way, can you LaTeX the full solution to this homework problem up for me? Plz see this page: ncatlab.org/nlab/show/(infinity,1)-category
@Blue maybe you can help me too
kthnxbai

Anonymous
@BalarkaSen O_o...hOmOtOpy....sEgAl space....all GrEeK to mE

Anonymous
7:22 PM
That's hw....omfg XD

Anonymous
@BalarkaSen bwahahahaha

Anonymous

Anonymous
@BalarkaSen Here's the solution to your hw question. ^

so it gives the desired result

Anonymous
@nasil Good!

7:28 PM
but i do not know how to repeat it until the integer "n"

Anonymous
@nasil Learn recursion dUdE

Anonymous
Or learn using loops

@nasil Do you understand what a function is? What you want to do is define a function that takes n as an argument and spits out the n-th fibonacci number.

spits out the members of the serie until the number "n" and the number "n"

@Blue thanks for your help. I'll post the same question on math.SE and physics.SE and ping 10 more different people I don't know because I didn't like your LaTeX font

7:29 PM
@ACuriousMind no i do not
in maths i do
i do not know how to create one in oython

Anonymous
@BalarkaSen 0001110010000000111100101010101010111100101100110001010011

@ACuriousMind If you couldn't get a research position (now or after your PhD), I suggest we start a restaurant together with AFT....
A lot of (easy) money in that
Other tech jobs (developer, etc. ) are bullshit

@nasil then you should look at whatever Python tutorial you like and learn that
Because it is what you want to do here.

@ACuriousMind that is the problem i am mainly dealing is not being able to find tutorials
there is always a feeling inside me that there could be a better one

Anonymous
@ııııııııııııııııııııııı Broring. You should start the world's most popular meme website with AFT

7:34 PM
and just annoys me keeps me from studying

Anonymous
I bet you'll be millionaires soon. (Of course AFT might flee with all of the money. No guarantee about that)

Anonymous
:P

@nasil Just pick one. If you feel it's above or below your level, try another one. Don't sweat the choice.

@ACuriousMind do you have a favorite

@Blue ...why do you keep writing "broring" instead of "boring"?

Anonymous
7:35 PM
@ACuriousMind Boring is Broring :P

Anonymous
I mean boring is boring

Anonymous
But whatever XD

@nasil I have forgotten which one I used to learn Python and it wasn't my first programming language, either, which changes considerably what one is looking for in a tutorial.

@ACuriousMind Why are you so brothered about that?

@BalarkaSen why do you crare?

7:37 PM
@Blue The good thing about a restaurant is that you both eat and make money

Anonymous

@ııııııııııııııııııııııı What culinary style did you have in mind?

@nasil I am a brofessional spelling-nazi.

Anonymous
Special Dental Care Food

@ACuriousMind Haven't decided yet....

Anonymous
7:40 PM
@ııııııııııııııııııııııı See my suggestion ^ ;)

Anonymous
Well, why the f*** am I procrastinating

Anonymous
:P

@Blue I'm an expert on that one

You mean brocrastinating.

@Blue That sounds as if we're selling dog treats, not people food :P

Anonymous
7:45 PM

@PrathyushPoduval impossible for my purposes
@ııııııııııııııııııııııı 2.60

Anonymous

@ACuriousMind so if a mod's account gets deleted there's nothing that can be done?

does anyone here have or think will have hair loss?
@ACuriousMind is it possible to delete your account on just one SE website?

@0ßelö7 Yes, deleted accounts are unrecoverable. But accounts simply can't so easily "get deleted".
@ııııııııııııııııııııııı Yes, I think most deletions are only on one site by default unless you explicitly trigger the deletion of your network account.

7:49 PM
Hair multiplication or hair cloning is a proposed technique to counter hair loss. The technology to clone hair is not yet available. Many millions of dollars were put into research on the subject by Aderans, but they have stopped researching it. Experts previously assumed that in the case of complete baldness, follicles are completely absent from the scalp, so they cannot be regenerated. However it was discovered that the follicles are not entirely absent, as there are stem cells in the bald scalp from which the follicles naturally arise. Abnormal behavior of these follicles is suggested to be...

Anonymous
@ııııııııııııııııııııııı I think I will have brain loss. Any cure for that?

@Blue Brain cloning?
(using stem cells)

Anonymous
@ııııııııııııııııııııııı Aha, that's what I need

@0ßelö7 $2.6 per liter?! Anonymous Buy a Tesla 7:52 PM This is the most downvoted answer on Physics SE -21 Is there an elegant proof of the existence of Majorana spinors? No. Because they don't exist. The neutrino is not a Majorana spinor. It's a Weyl spinor. See Dirac, Majorana and Weyl fermions by Palash Pal. He said “the neutrinos had to be uncharged because of conservation of electric charge,... @Blue crack GR and travel using a customized wormhole @Blue Same here :/ I have tons of work to do @ııııııııııııııııııııııı who the fuck uses liter? Gallon @0ßelö7 Liter is the universally accepted SI unit for volume The strongest military and economic force in the world uses gallon. Get with the program. @ACuriousMind yep basically that. 8:07 PM @heather: I have an answer for you. =D =D =D =D ^the above times infinity Q: "What is the mathematical representation of the operation that type I SPDC performs on the polarization of photons, with a photon being represented by a|0> + b|1> (i.e., the standard representation of a qubit in a quantum computer)? Would the representation be dependent on the dimensions of the BBO crystal(s) used?" A: Sure check out §II.D.2 in the beautiful paper http://dx.doi.org/10.1103/PhysRevA.63.042310 The representation is independent of the dimensions of the BBO - length is parameter of unitary operator and width etc fixes the mode of interest. Here's a link to the arxiv version: arxiv.org/pdf/quant-ph/0010049.pdf Anonymous @0ßelö7 Russia uses the Metric System ;) @ACuriousMind how does it work? @Blue that's not even a good troll and a link to the published version: hdeguise.lakeheadu.ca/pdffiles/bellinequality.pdf 8:09 PM At least say China thank you, let me take a look @0ßelö7 The strongest military force in the world is Russia Anonymous ^ the section titled "2. Pair generation using PDC" ? @heather Yes I suppose so. I gotta run... 8:11 PM Wot I will check it out later myself but now no time... :( okay @ACuriousMind am I allowed to call him insane? oh gosh i have no hope > Consider the action of an SU(1,1) transformation, generated by the realization corresponding to either the degenerate PDC algebra of Eq. (2.19) or the nondegenerate PDC algebra of Eq. (2.20), on the vacuum state |0>. I may get a different answer a different person.. but this is what I got now. 8:13 PM i do appreciate your help, perhaps it'll become clear after some staring. @heather sounds like physics Gerry and Knight is probably a better place to get warmed up on the topic. Bye for now. at least it's better than maths @0ßelö7 @ZeroTheHero okay, have a good day =) @ACuriousMind with the answer you linked to me, is it reasonable to consider, basically, the$V$polarization axis as sort of like the one state and the$H\$ horizontal axis as sort of like the zero state (or vice versa)? Because if so, I think that answer makes sense to me.

@heather the key part seems to be after Eq.(2.20):
> . That is, a pair of photons is created in the same polarization in type-I PDC and a pair of photons is created in opposite polarizations in type-II downconversion.

[Some rant inspired logic question]
Prerequisites:
The Hardest Logic Puzzle Ever is a logic puzzle so called by American philosopher and logician George Boolos and published in The Harvard Review of Philosophy in 1996. Boolos' article includes multiple ways of solving the problem. A translation in Italian was published earlier in the newspaper La Repubblica, under the title L'indovinello più difficile del mondo. It is stated as follows: Three gods A, B, and C are called, in no particular order, True, False, and Random. True always speaks truly, False always speaks falsely, but whether Random speaks truly or falsely is a completely random matter...
Fatalism is a philosophical doctrine that stresses the subjugation of all events or actions to fate. Fatalism generally refers to any of the following ideas: The view that we are powerless to do anything other than what we actually do. Included in this is that humans have no power to influence the future, or indeed, their own actions. This belief is very similar to predeterminism. An attitude of resignation in the face of some future event or events which are thought to be inevitable. Friedrich Nietzsche named this idea "Turkish fatalism" in his book The Wanderer and His Shadow. That acceptance...
Warning: The following content based on the hardest logic puzzle ever contains rant
Suppose you are a patient affected by coughing with 4 possible scenarios:

8:17 PM
@heather 👿

1. Chronic: For every second, you cough
2. Dormant: For every second, you will not cough
3. Random: For every second, there's a chance that you will or will not cough
4. Wicked: For every second, the occurence of coughs occured in a way to maximally make you suffer
The logic question, is to devise a suitable mindset, medication, environment etc. ,such that no matter what the nature of the cough is, you minimise the suffering
What we know: We know from the solutions to the hardest logic puzzle ever and its extension, the solution to 1-3 exists
However: Is there exists a solution to a wicked cough?
More philosophically, is metafatalism possible?
and now...
Why is the above contain a rant: A wicked cough prevent me to get sleep last night and I was forced to wake up at 6:00
O and btw, some dictionary:
Metafatalism: The subjugation of everything including fate itself such that no matter what it choose to do, it cannot affect the outcome
In simple terms: Trapping fate itself in a state of And I Must Scream

In more engineering terms: A system that is so robust to noise and uncontrolled factors such that now matter how they occured, they become part of the system

And finally: So much crazy thought inspired from poor sleep!

8:22 PM
@ııııııııııııııııııııııı and the US could destroy every country on the face of the Earth. Counting WMDs in strength is retarded.

@heather There are actual problems with that answer though - There's a probability of obtaining more than 2 photons at once, it doesn't mention the timing issues (to be fair, they're not normally issues - all the photons don't just magically appear at the same instant) - the process is spread throughout the crystal, the photons are emitted in cones, they don't all have exactly the same wavelength

::groans::

Anonymous
@ııııııııııııııııııııııı I think we should avoid posting pictures of controversial leaders in this chat room esp. dictators.

Anonymous
Mentions of NK makes me sick anyway...

8:25 PM
Oh, the number of photon pairs produced depends on the length of the crystal. The list goes on

Congratulations @heather - you have been awarded the achievement Discover physics is not linear

@Mithrandir24601 lol

@BalarkaSen Now do "roflmao"

8:30 PM
Feeds is mean :-(

@AccidentalFourierTransform This is violence against men

@ııııııııııııııııııııııı so what?

@AccidentalFourierTransform People have already announced their frustration with this by electing Trump

I am pro-violence and pro-Trump so I don't get it

8:36 PM
@Secret Disappointing: not rolling on the floor

@AccidentalFourierTransform Everybody has a Trump inside....your job is to not awaken it in the first place, and slowly suppress and finally defeat it.

@heather Yes

@ııııııııııııııııııııııı Geoff New, huh?
Definitely worth a look

@ACuriousMind so the answer makes sense, but @Mithrandir24601 says it's incomplete and is not a full answer =(

Geoff New is fantastic
I love his talks

8:43 PM
@ııııııııııııııııııııııı My Trump want to destroy the world and ensure it stay destroyed forever

@Secret What the fuck?

He's like a general giving a briefing in an old-school british wwii flick

@heather Sure. But do you care about these issues for your purposes?

@ııııııııııııııııııııııı "Everybody has a Trump inside" there is an Ivanka joke somewhere there

@ACuriousMind When you're trying to do an experiment and the end of the answer contains the phrase "So, without considering the various experimental complications that can limit this in practice"...

8:46 PM
Can we turn the meme dial a bit down again please?

27 mins ago, by Secret
Why is the above contain a rant: A wicked cough prevent me to get sleep last night and I was forced to wake up at 6:00
::apologies to 0celo for strong language::

Anonymous
@Secret I have a bad cough too since the past few days. The best solution is to not sleep at night. :p

I already don't have enough sleep of 4-5 hours per night, the cough makes it even worse
(meanwhile coughing off screen)

Anonymous
Sleep in the morning in that case (?) I feel sleepy by 5am and the cough can't keep me awake

@ııııııııııııııııııııııı random bit of G New lore: having discovered third-harmonic generation in the sixties, and worked in nonlinear optics all the way through to emeritus professor, one good day the physics department decided that it didn't have enough space and that the emeritus offices needed to be converted into a PhD student bullpen. At which point, you'd see him happily sidling up to his desk at the bullpen, between two PhD students.

8:51 PM
I did have see a doctor and took medication, but so far it is quite slow acting
also the cough is wicked because it gets worse only at night

At some point he did leave, though, and I inherited his copy of Numerical Recipes ::grin::

lol
Is there anything (of the talks you mentioned) available online?
by the way, has the YouTube logo color changed recently?! It looks brighter than before for me

9:15 PM
@ııııııııııııııııııııııı Yeah, yet another redesign.
@AccidentalFourierTransform @BernardoMeurer The cult starteth. I'm sending this now for printing.
^ PGP enlightenment

9:37 PM
@JaimeGallego nice! it looks great
did you design it?

I did, but it took me more time than I care to admit.
Learned lots though.

@JaimeGallego Dope!

@ACuriousMind how does one pronounce Orlicz?

10:32 PM
@0ßelö7 no idea

@ACuriousMind Do we have any Polish people here?
I know a Pole IRL but I don't want to talk to him

I don't think any of the regular chatters are Polish

10:51 PM
@ııııııııııııııııııııııı not that I'm aware of
Would like to have one handy though

@ACuriousMind according to los Google, it is a -ch at the end

For occasions such as this one

11:02 PM
@heather the paper is actually fairly straightforward but technical. It may only partially answer your question; we'll find some time during the week to make sure you get all you can from it. TTFN

@ACuriousMind is it Way-el or Why-el?

stupid question of the day: how do you convert a torrent file into something readable?

@0ßelö7 I have no idea what you're talking about

@ACuriousMind I might need to say Weyl in a talk and don't want to look like a fool

@heather If you mean a fire with the ending .torrent, that usually doesn't contain the data you want, but only the metadata information for the torrent program on where to download it from.

11:14 PM
@ACuriousMind yeah, .torrent.

@0ßelö7 Ah. Then the latter, just like the German subjunction meaning 'because'.

erm...how do i get the file then?

@heather You need a BitTorrent client program that can read the .torrent information and initiate the actual download. What are you downloading that offers a torrent but not a traditional download?

erm... a book off of libgen

Are we really teaching her how to illegally download pirated media on the chat?
Seriously?

11:19 PM

@heather Ah. You might want to be careful with that because there's no actual guarantee the torrent will be what it promises (i.e. illegal torrents are one of the ways malware is spread)

@0ßelö7 Nothing about the BitTorrent protocol is inherently related to illegal content.

@ACuriousMind i guess i'll just not then
maybe i can find what i'm looking for another way.

why didn't you get the djvu from libgen

11:23 PM
where do you find that?
i'm not seeing it.
actually, nvm
i found a pdf a different way.

11:42 PM
@heather are you good to go over this later in the week?

sure - tonight, later in the week, this weekend.
i just don't really get any of it right now, tbh.

0

I am currently writing up a 'basic electronics' student workbook and am up to the point of explaining conductors, insulators and semiconductors. It was my understanding that all metals are conductors (to varying degrees) due to the fact that they had one, two or three valence electrons which were...

yeah that's ok... It hasn't been cited much so don't feel bad about it.
I have to fix some stupid code like ** right now ** but I will prepare a sharable file and we can start from there.

okay.
thank you again!

I started already as my code runs some set up calculation.

00:00 - 17:0017:00 - 00:00