The h Bar - 2016-07-05

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user54412

2:06 AM

@Sanya When in doubt, just ask on Meta. There's generally no downside. (I mean, don't invest three days crafting the perfect question, since it might be deemed unsuitable there and then your work will feel wasted.) People might downvote, but on Meta that doesn't affect your reputation.

@ChrisWhite Good evening

user54412

That's like the least trolling thing you've said this past month :p

screw you

user54412

:(

contrary to your beliefs, I do not consciously troll

Alfred Centauri

2:11 AM

@0celo7 you're a philosophical zombie troll?

2

no

I'm not a troll

user54412

@Danu I need tikz help :( Why is this so cumbersome, and why do the tex.SE people always use it for anything relating to graphics?

Alfred Centauri

@0celo7 That's exactly what a philosophical zombie troll would say ergo...

@AlfredCentauri no

@AlfredCentauri For instance, it is possible that for $f,g\in\mathbb F_p[x]$ we have $f(x)=g(x)$ $\forall x\in\Bbb F_p$, but $f\ne g$.

so there goes your theorem

i.e. "walks like a duck, talks like a duck" is wrong

It does not have to be a duck.

user218912

3:03 AM

I finally found a roommate.

@ChrisWhite It's a kind of masochism. And I'm being sucked in, too.

user218912

and my roommate likes the colour blue.

user54412

4:07 AM

@JohnRennie and it just completed, apparently exactly as planned

user54412

though the science instruments won't be activated for a couple days, and the next close flyby will by in a couple months

user54412

(that's a crazy elliptical orbit they're on)

user54412

4:19 AM

@dmckee All I want is to position a graphic at some point on the page. The tex.SE answer begins "quite easy to use" and proceeds with 8 paragraphs followed by 20-lines of arcane @-strewn tex templates just to define a coordinate system on the page. This can't actually be a sensible thing to do, right?

4:35 AM

0

Q: What's wrong with this question? Why did it get downvoted?

Can relativistic mass be treated as rest mass? It seems clear, pointed, and of broad interest. I doubt most introductory students of physics could answer it without thought.

5:23 AM

“Did Einstein Kill Schrödinger’s Cat? A Quantum State of Mind” / aaronson

5:40 AM

When a neutron decays, is it necessary for a anti-neutrino to be released, if electron carry 0.782MeV of energy?

@AnubhavGoel Lepton number has to be conserved. An electron has lepton number +1 and the anti-neutrino has lepton number -1, so they add up to zero. Since the initial lepton number was zero this means lepton number is conserved.

@ChrisWhite we get used to this sort of thing and forget how frakking amazing it is! :-)

5:54 AM

If you are given a neutrino and anti-neutrino, how do you find which one is which?

aloha

That depends what you're asking. In beta decay we know it has to be an antineutrino because it has to have a lepton number of -1 to balance out the electron.

However if you see you see a neutrino from an unknown source whizzing by and you ask whether it's a neutrino or antineutrino that's harder. As far as we know all neutrinos are left handed and all antineutrinos are right handed, so you can tell by measuring its helicity.

But it's possible that neutrinos are Majorana fermions, in which case they are their own antiparticles.

user54412

@JohnRennie What really wowed me was how casually they were talking about the computer rebooting if it had too many radiation-induced errors, whereby it would figure out where it was and continue with the maneuver.

user54412

6:10 AM

I have enough trouble coding on computers that don't randomly flip bits. And we're talking not just data bits, but instructions too!

@JohnRennie When a neutron decays, if electron carry 0.782MeV of energy, how much E energy does neutrino carry?

@ChrisWhite indeed :-) I hadn't realised just how bad the radiation is until I read that Juno can only do 36 passes though the most intense radiation before it's basically fried.

@AnubhavGoel in beta decay the total decay energy is 1.16 MeV and this is shared between the electron and antineutrino. So the electron doesn't always have 0.782MeV. Its energy can be anything from zero to 1.16 MeV. This apparent non-conservation of energy was how the neutrino was first discovered.

Damn, I need another (pint mug of) coffee, and I've only been up two hours. Some mornings it's hard to get going. Thank goodness the Physics SE exists or I'd have to do some real work.

user116211

6:26 AM

@yuggib: Have you read the New Foundation Set Theory?

user116211

Does it permit the Universal Set?

@JohnRennie hyperphysics.phy-astr.gsu.edu/hbase/particles/proton.html This page is confusing me. Why have they shown Q=0.7823MeV, when it's 1.16MeV

user116211

In $\sf ZF$, do we need Axiom of Regularity along with permitting the weaker version unrestrained Comprehension schema axiom to defeat Russell's Paradox?

user116211

Also, a noteworthy line by Jech:

user116211

> The Separation Axioms are too weak to develop set theory with its
usual operations and constructions. Notably, these axioms are not sufficient
to prove that, e.g., the union $X ∪Y$ of two sets exists, or to define the notion
of a real number.

user116211

6:31 AM

I'm going to look into it further.

user116211

@JohnRennie: Farage washed his hands of Brexit.... how clever guy he is ;(\

user116211

@3750 Good!

@JohnRennie Oh! I get what they meant, they decreased mass energy of electron from 1.29

Well! I meant that from the free energy available 0.783MeV, if electron takes 0.7819MeV, some proton, how much did neutron get(KE+MassE)?

Somewhat reluctantly I have to do some real work for the next hour or so. Back in a bit ...

6:52 AM

I have a question about the purcell effect, which is basically the enhanced relaxation rate gamma rate of an atom in a cavity. It is given by kappa*g/delta, where kappa is the linewidth of the resonator (omega/Q), g is the coupling between the atom and the resonator and delta is the detuning between the relevant atomic transition. Lets assume high anharmonicity so that other levels don't play a role. How am I supposed to interpret the effect? Continuing on the next line

As in, say that the numbers are such that I get a gamma due to the purcell effect of 3 MHz. My relaxation rate is 3 MHz higher, I get that. But from the resonator point of view, what do I see? If I look at its output, do I see an enhanced transmission at the qubit frequency? Something like a lorentzian with a 3 MHz linewidth?

@ChrisWhite One possibility to achieve that might be to code everything redundantly, i.e. you have the same instructions and the same data at different memory locations. At specific time intervals, or after a heavy calculation, these redundant memory locations are compared, and if there are too many differences, you reboot.

Did they say what kind of persistence they use?

@MAFIA36790 No I haven't, but I strongly doubt it

it seems thta he does a trick to avoid the paradox

e.g. it does not allow $x\notin x$

i.e. it allows only for some formulas, not every formula

there are also set theories, like bernays-goedel that alllow for two types of objects, sets and (proper) classes

7:11 AM

What do you need, @ChrisWhite? I know it's cumbersome, but as with everything one can grow accustomed to it

What's nice about tikz is that you can keep everything inside tex

user116211

@yuggib ohh.

@ChrisWhite picture positioning? That's not really tikz, is it?

user54412

@Bass I haven't looked into it.

user54412

@Danu Well, I want to manually put an image outside the flow of things, in beamer. And the Masters all say to put the \includegraphics inside a tikz node.

user54412

I think I finally hacked something workable.

user54412

7:20 AM

It's times like these that make the weak go back to power point. But I will endure. No sacrifice is too great for software ideology.

2

7:35 AM

@ChrisWhite that does make some sense.

So you're just using invisible lines or what

To adjust the position

7:55 AM

@ChrisWhite thank you :)

8:08 AM

@AnubhavGoel in the question you've just posted what does which orbit/shell/value of n does it belong mean? Are you asking about the electron? If so it's a free particle and isn't in any orbital/shell.

@AaronAbraham you're welcome. Re problems/Iridov/whatever: getting good at doing these is just practice. There are only so many variations of mechanics problems and if you work your way through Iridov you'll basically have done them all.

In my day we used the Cavendish Problems in Classical Physics booklets to get up to speed. I don't know if these are still published. Amazing I still have my copy from my first year in university in 1980.

If you want to do well in the exam then just work through all the problems until you can do them in your sleep. That's pretty much what I did for my finals. Then once the exams were over I forgot it all again and got a life instead.

8:23 AM

@JohnRennie You mean n=∞

@AnubhavGoel the electron was never in a bound state. The energies involved are vastly greater than typical atomic binding energies.

Wow so strong form, just means Euler-lagrange equations and weak form, is the full thing with integrals

hmm

lolz because it is stronger hahahaha

8:51 AM

Strong form is basically useless unless you have some weird boundary conditions

@ChrisWhite off the top of my head, something like shift={(current page.north west)},shift=(2,-2) puts the (0,0) coordinate of your picture 2 cm down and 2cm over from the top left corner. I do this all the time.

You might also need the overlay option to prevent the picture from messing up your layout.

Recent Questions - Physics Meta Stack Exchange: How to deal with “spam” for papers?

posted on July 05, 2016 by Wrzlprmft

I noticed some answers that: have nothing or little to do with the question; include an undisclosed link to a paper that is either by the answer’s author or particularly liked by the answer’s author – as evidenced by their profile and number of links (22) to that paper in other answers. If we take the current wording of the spam flag (“Exists only to promote a pr…

9:07 AM

"Do not tell me I cannot sum infinite series without regularization. I can. I will not provide details on how I do this."

lel

@JohnRennie What about," I meant that from the free energy available 0.783MeV, if electron takes 0.7819MeV, some proton, how much did neutron get(KE+MassE)?"

@AnubhavGoel The neutron doesn't exist after the beta decay, so how can it get any of the energy? Or did you mean how much does the neutrino get?

9:25 AM

No come on Luboš, tell us what you really think.

0

A: What's wrong with this question? Why did it get downvoted?

I've just added another (just second) negative vote to the original question once my suspicion was confirmed: It is not really a question, it is an attempt to promote obvious misconceptions about relativity. Dmckee gave an answer (which I upvoted). Some of its general lessons are: One should d...

9:57 AM

@ChrisWhite it's on my blog too

10:24 AM

@JohnRennie Sorry it was a typo!!! What about," I meant that from the free energy available 0.783MeV, if electron takes 0.7819MeV, some proton, how much did neutrino get(KE+MassE)?"

Hey! Is there some change in bounty system? I wanted to start a bounty on someone else's question. It showed I need to give +100 minimum rep. Last Time I gave +50. What just happened?

3

Q: Charging by induction

When we charge an conductor by induction and grounding, we first bring a negative charge to the conductor. As a result the mobile electrons of the conductor get repelled and stay far from the negative charge. After we ground that conductor and then those repelled electrons go to the earth. But ...

electrostatics electricity potential-energy superconductivity voltage

I can spare +50, but +100s double, I won't

11:21 AM

@JohnRennie Good morning my formerly European friend.

12:06 PM

@0celo7 soon(?)-to-be-former-european friend

@yuggib Why the question mark?

@0celo7 not formerly European just yet :-)

It'll be two years from the moment article 50 is invoked, but when that is depends on who becomes prime minister.

what is that anyway

Article 50 is the clause that allows any member of the EU to leave.

@yuggib I tried to teach my 6yo nephew some geometry, he said "no"

I tried to teach him some topology, he said "no"

Analysis, "what's that"

12:19 PM

lisbon-treaty.org/wcm/the-lisbon-treaty/…

He's Asian too, stochastic analyst confirmed

@JohnRennie hmm, why not initiate it now

@0celo7 The leavers want to invoke it now and get the hell out. The remainers want to negotiate first, then invoke article 50. The subtext is that if the negotiations go well enough we might decide not to leave after all.

Well it seems to me like there was a lot of bullshit flying around the leave decision

That people thought it would not rek the economy

Basically the UK wants everything they currently get from the EU, but without freedom of movment i.e. we want to be able to throw out all those pesky foreigners.

But keep the free trade.

But if the EU grants us that all the other countries will want it as well and the whole thing will fall apart.

I hear the Netherlands and maybe France have leave movements brewing

12:24 PM

Every European country has some fruitcake demagogue who wants to leave the EU. However in no country other than the UK is this more than a minority position.

"fruitcake demagogue"

I'm not sure what that means, but it's probably not nice

And even in the UK 51.9:48.1 was hardly an overwhelming win for the leavers.

Be nice Mr. Rennie

@JohnRennie Any idea what the turnout percentage was?

And were immigrants allowed to vote or only citizens?

High. 72% I think. Only holders of UK passports could vote.

Oxford English Dictionary: "fruitcake demagogue" - see "Nigel Farage"

I've seen him in a few debates and liked what I've seen.

But then again I'm sure one side is lying through their teeth.

This is why politics is getting boring for me.

Especially in America where one side is completely unlikable and probably lying and the other is confident enough to spout lies as truth.

So both sides could be lying through their teeth.

I really hope Trump doesn't pick Christie Kreme as his running mate. I would have to say a dozen prayers before voting.

12:32 PM

Have to go shopping now. Back later.

@JohnRennie cheerio old chap

@Secret want to write an essay for me?

I am not an essay machine. The closest thing I can do is give suggestion, but it depends on how well I knew a topic

I think it is a logical deduction from the fact that an incredibly violent outward explosion occurred, and that that explosion and the fact that matter seems to have been originated from the same point both result from one and the same event. It could be wrong of course, but a theory claiming that all matter was globbed together and then accelerated away at the speed of light for no apparent reason is no better. I don't believe we have any direct evidence of this though. It's a bit like assuming the earth is round purely on the basis of the fact that it has shown to curve. — Neil 1 hour ago

::sigh::

@Neil As a cosmologist, I agree that such a theory claiming matter to have all been at the same point and then have exploded outward at the speed of light is nonsense and probably wrong. Thankfully, that is not at all similar to the actual Big Bang theory. Phew! We really dodged a bullet on that one. — Jim 3 mins ago

@Jim so what is your job now?

Are you going to get your PhD

@0celo7 Physics lab coordinator at University of Toronto: Mississauga. And yes, I fully intend to get a PhD in cosmology

12:38 PM

@Jim please don't be devoid of life like one of our lab coordinators

I wanted to pick up something I ordered for work

I asked here where the package was

@0celo7 lmao, I am one of the farthest things from that

"I don't know, look for it"

Then I wanted to return an extension cord I borrowed from her colleague, but he was not in at the time

did it make sense to ask her?

I wanted to put it by his desk

She said "just pile it on the floor somewhere"

@Jim Yes, she accepts all our mail

She's never in a good mood and her pants probably fit her 10 years ago in high school

ah, then yeah. Sounds jaded

so she's young

12:41 PM

@Jim Well, her office does. We have 2 lab coordinators but the mail was literally next to her desk

Her colleague would at least offer to help go through the mountain of packages

And I find it weird that you can just walk in and grab packages

see, I have nothing to do with mail. Students only come to me when it's lab time or for questions about homework

@Jim Ah, we have to send emails to those guys w/ account numbers and they order anything we need

prevents students from buying ridiculously expensive stuff because they (lab staff) know how to shop around and prevents profs from having to worry about buying shit

I can't imagine any situation here where a student would need to order something through the school and they wouldn't have some sort of supervisor who would do it for them

our students obtain quotes. The profs then get quote and say "Yup, looks good, I'll order it" or "Nope, too expensive, find a cheaper one"

different systems

wait what questions about homework?

I would not go to these guys about homework questions unless it was like FORTAN stuff

they do department IT too

We're a small department compared to physics but the largest in the US, I think

@ACuriousMind Have you seen the LC connection defined like this? $2\langle \nabla_YX,Z\rangle= L_Xg(Y,Z)+\mathrm d X^\flat (Y,Z)$?

1:04 PM

@ACuriousMind What is "differentiable" and "smooth" in El Deutsch

ableitbar?

@0celo7 No

glatt?

@0celo7 ableitbar/differenzierbar and glatt.

@ACuriousMind It's a generalization of the fact that a vector field on $\Bbb R^n$ is constant iff it is simultaneiously a Killing field and a gradient.

@0celo7 they're already saying that it will take years for them to leave the EU

@0celo7 try "category theory"

1:06 PM

@0celo7 general questions about physics homework. I was just as surprised as you, but that's the way it is here and I can help so why not

@yuggib I've already left, but I will next time I visit them

@yuggib how does one show part 2 directly w/o Frobenius?

user image

I'm not sure if the problem wants me to use Frobenius or not...

The proof using Frobenius should be in Lee.

Either Lee MDG or Lee SM.

Maybe KMS too.

@ACuriousMind Do you know? Probably not...

1:46 PM

@ACuriousMind Ah, to prove that the restricted holonomy is a Lie subgroup one needs the follow Theorem: Let $H\subset G$ be a subgroup of the Lie group $G$. If every $h\in H$ can be connected to $e$ by a $C^1$ curve in $H$, then $H$ is a (connected) Lie subgroup of $G$.

This requires a nice black box theorem

2:24 PM

@JohnRennie wondering about this. isnt the radiation mainly from the sun? which hits everywhere/ "evenly" except the shadow side of the orbit? or is there something localized in the flyby area? are you saying the probe will eventually malfunction from radiation exposure & its age is related to that? (which doesnt sound right...)

Jupiter has a very strong magnetic field, and that traps then accelerates particles from the Solar wind. That's what creates the very high radiation levels.

@0celo7 what did you order? are you doing (gasp) experiments? o_O

I think it's basically Jupiters version of the Van Allen belts.

@JohnRennie were these even known to exist prior to this mission? never heard of them before... its 1st ever case of the aurora being measured isnt it?

Juno's orbit needs to get very close to Jupiter, and that means having to go through the belts. However the orbit has been chosen to minimise the radiation exposure. Even so, 36 orbits is all it gets, then sizzle.

2:28 PM

@vzn I'm an experimentalist.

@vzn It's not the aurorae. The radiation belts are quite separate. We've known for ages that they existed, hence the carefully chosen orbit and the radiation hardening for the Juno mission. As I say, Earth has them too, but Jupiter's radiation belts are much, much stronger.

what do you mean its not aurorae? afaik it was visualized 1st time ever in that recent image

re brexit, ran across new interesting pov alternet.org/world/brexit-vote-shouldnt-shock-global-elites ... my current model which fits USA/UK both is a rough idea of "shared prosperity". public has a sense of whether there is shared prosperity, loosely or closely linked to inequality/ estimated by difficulty of finding good paying/ full time jobs. if its hard, public concludes there is low shared prosperity & then is more in the mood to reject foreigners/ immigrants.

I mean the aurorae are a different (though related) phenomenon. See:

Magnetosphere of Jupiter

The magnetosphere of Jupiter is the cavity created in the solar wind by the planet's magnetic field. Extending up to seven million kilometers in the Sun's direction and almost to the orbit of Saturn in the opposite direction, Jupiter's magnetosphere is the largest and most powerful of any planetary magnetosphere in the Solar System, and by volume the largest known continuous structure in the Solar System after the heliosphere. Wider and flatter than the Earth's magnetosphere, Jupiter's is stronger by an order of magnitude, while its magnetic moment is roughly 18,000 times larger. The existence...

First detected in the 1950s and measured precisely by Pioneer 10 in 1973.

ie something like "if its hard for me/ friends/ family then we shouldnt let other people in either/ yet"

seems a bit wild to me the hubble didnt find aurorae until recently if magnetosphere has been known since 1950s. seems like some kind of gap/ likely some kind of story there

@vzn I gave up trying to understand my fellow citizens years ago. They're all completely mad except for you and me ... and I'm not so sure about you :-)

2:40 PM

@JohnRennie lol. how churchillian of you. ("democracy is the worst form of govt except for all the others") alas "understanding fellow citizens" may be a crucial part of an enlightened democracy (and political unions!)...

@ACuriousMind Apparently one can Fourier transform on a symmetric space.

Actually I think the Brits generally manage things quite well. We managed to keep a remarkable amount of political stability over the last millenium. I think the British are arch-compromisers and that works well in stopping us from getting too extreme.

All the Brexit hoohaa will eventually peter out into a compromise that pleases no-one but leaves no-one hopping mad either.

@ACuriousMind Ok wtf Helgason defines Lie groups as groups that are analytic manifolds, what's up with that

can one always turn a smooth manifold into an analytic one?

@JohnRennie personally think its a permanent gamechanger in intl politics signalling the end or at least decay of "reagan-thatcher" neoliberalism (holding sway/ grip for 3-4 decades) :)

We'll see.

2:47 PM

@0celo7 so?

@ACuriousMind we once talked about Fourier transforms on a general manifold

@0celo7 No, but Lie groups are indeed analytic

???

I've never heard this before

@ACuriousMind Hmm, what's an example of a smooth manifold which cannot be given an analytic structure?

I do not understand the proof given on MO of this fact

I have no clue what they're even trying to do there

3

Q: analytic structure on lie groups

I need a reference for a result I have heard only very vaguely "A lie group (smooth) has a compatible analytic manifold structure". (Would even appreciate a concise way to refer to the result..) I gather from a discussion on a related question that "There is an amazing theorem of Morrey and Gra...

lie-groups smooth-manifolds reference-request

2:54 PM

@BalarkaSen Hm, maybe the answer is "yes" and all smooth manifolds are indeed analytic

I don't see how I would prove that either, actually.

38

Q: Can every manifold be given an analytic structure?

Let $M$ be a (real) manifold. Recall that an analytic structure on $M$ is an atlas such that all transition maps are real-analytic (and maximal with respect to this property). (There's also a sheafy definition.) So in particular being analytic is a structure, not a property. Q1: Is it true th...

differential-topology dg.differential-geometry gt.geometric-topology

Something something Nash: realize it as a real algebraic set and then I think real algebraic sets are also analytic subsets of R^n.

It appears to be another variant of that Whitney smoothing

I've never heard of this before, what the hell

2:58 PM

Hmm, looks like Greg Kuperberg mentioned my idea.

The MO proof is taken from Kolar et al.

@0celo7 Heard of what?

It makes just as little sense there as on MO

@BalarkaSen Lie groups are analytic

(by "analytic subsets", I meant can be given structure of an analytic submanifold)

does the existence of analytic maps imply the manifold is analytic?

3:00 PM

But I am unsure how to make my idea work because I may have to cut my manifold out by nontransverse functions.

ok, so I get that multiplication $\mu$ is $C^\omega$ near $e$

(indeed, to cut out by transverse smooth functions even, I need my manifold to have stably trivial tangent bundle)

Why does this imply it's $C^\omega$ everywhere?

@0celo7 I think because the Lie group is generated by every neighbourhood of the identity

@ACuriousMind I know that, but I don't see what that does for me.

oh, derp

@ACuriousMind Is the German hack worth getting?

In German?

user218912

3:11 PM

should I do 7 courses in first semester?

@0celo7 So far, I'd say yes

http://physics.stackexchange.com/questions/266350/is-the-strange-connection-between-subatomic-particles-trans-dimentional

The closest thing that is similar to what the op had in mind is some proposal that suggest wormholes to explain entanglement, which (I refuse to comment as I knew nothing about it other than pop sci explanations)

@ACuriousMind So the German voice acting is tolerable?

@0celo7 Yes, and since it is made by Germans I would not expect the English one to be better in any case

(unless one inherently finds the English language superior ofc)

3:21 PM

Any good place to visit at luxenbourg besides Vianden castle?

3:32 PM

luxembourg is a real place?

Luxembourg /ˈlʌksəmbɜːrɡ/ (Luxembourgish: Lëtzebuerg; German: Luxemburg), officially the Grand Duchy of Luxembourg, is a landlocked country in western Europe. It is bordered by Belgium to the west and north, Germany to the east, and France to the south. Its capital Luxembourg City is together with Brussels and Strasbourg one of the three official capitals of the European Union and seat of the European Court of Justice, highest juridical instance in the EU. Its culture, people and languages are highly intertwined with its neighbors, making it essentially a mixture of French and Germanic cultures...

Hmm, I thought it was a meme.

Yes, it is sandwiched between germany, france and belgium

and I am there right now, just visited Vianden castle

Apparently super linear algebra is a thing.

Since its neighbour is germany, I figure acuriousmind might have some nice recommendation

3:36 PM

I have never been to Luxembourg and have no idea what there might be worth seeing there

ok nvm

Huh, apparently the exponential map is a natural transformation

> $\delta p\sigma$ stands for the trace of the matrix

Award for worst notation ever?

user54412

4:05 PM

@JohnRennie Also Io contributes to that.

(Correction)
Given the density matrix of the state $\lvert @\rangle=\sqrt{\frac{1}{3}}\lvert ud\rangle-\sqrt{\frac{2}{3}}\lvert du\rangle$

$$\rho_{AB}=\begin{pmatrix}0 & 0 & 0 & 0\\0 & \frac{1}{3} & -\sqrt{\frac{2}{9}} & 0 \\ 0 & -\sqrt{\frac{2}{9}} & \frac{2}{3} & 0\\ 0 & 0 & 0 & 0\end{pmatrix}$$

For the z direction
$$P(uu)=P(dd)=0$$

$$P(ud)=\lvert \langle @ \rvert ud\rangle\rvert^2=\frac{1}{3}$$
$$P(du)=\lvert \langle @ \rvert du\rangle\rvert^2=\frac{2}{3}$$
Anticorrelated spins in z
$$=P(du)+P(ud)=1$$

user54412

@DavidZ That's a really good explanation. There must be half a dozen separate questions on this on Tex.SE, and some of them have something similar, but the first I found was this, unfortunately.

$$P(rr)=\lvert \langle @ \rvert \frac{1}{2} (\lvert uu\rangle+\lvert ud\rangle+\lvert du\rangle+\lvert dd\rangle)\rvert^2=\lvert\frac{1}{2}\left(\sqrt{\frac{1}{3}}-\sqrt{\frac{2}{3}}\right)\rvert^2=\frac{1}{4}\left(1-\frac{2\sqrt{2}}{3}\right)$$
$$P(ll)=\lvert \langle @ \rvert \frac{1}{2} (\lvert uu\rangle-\lvert ud\rangle-\lvert du\rangle+\lvert dd\rangle)\rvert^2=\lvert\frac{1}{2}\left(-\sqrt{\frac{1}{3}}+\sqrt{\frac{2}{3}}\right)\rvert^2=\frac{1}{4}\left(1-\frac{2\sqrt{2}}{3}\right)$$
$$P(lr)=\lvert \langle @ \rvert \frac{1}{2} (\lvert uu\rangle-\lvert ud\rangle+\lvert du\rangle-\lvert d…

correction: line $P(ll)+P(rr)$ of "anticorrelated spins" should be $P(lr)+P(rl)$

@Acuriousmind does the above look correct?

4:25 PM

Lol some European dude came to subway asking for a 15 inch half foot sandwich

Omg was he asking for 15 cm

15 inch is roughly 1.5 hand spans

A hand span roughly 20cm from left to right

He might be askign for a submarine sandwich (those things that you get from the store Subway)

@Secret I have to be honest, sometimes you say stupid things

Of course he's asking for a sub

@ACuriousMind What measurements do you guys have in European subway?

that is because I wrongly interpret the word "subway" in your post as an actual subway, as in the underground, and I thought you encountered that guy in the subway

The bad thing about words with multiple meanings

@0celo7 15cm and 30cm, I think

Haven't been to Subway in ages, but I think that's it.

Aha, that explains it.

He was very confused at the notion of a 15 inch sandwich

4:46 PM

@0celo7 though a 15 inch sub sounds pretty good to me :-)

Actually that could mean a 15 inch sub-woofer, which also sounds pretty good ...

5:09 PM

@ChrisWhite ugh, yeah, that's a mess.

@JohnRennie agreed

0

Q: Unable to reply to a comment directly

There must be a reply option under each comment, So that I click on it, and reply to that comment directly, rather than writing new comments, again and again!. (for example: see facebook)

@JohnRennie he was a skinny dude though

@0celo7 Well my body mass index is 21 and I'd eat a 15 inch sub. Hell yes :-)

Though I suspect a 15 inch sub-woofer would be a bit too chewy for me.

@ACuriousMind I found a legit math book that uses $ds^2$ for the metric.

They even write $ds^2(X,Y)$

user image

5:23 PM

is that a bread with a piece of meat inserted

In the sense that most sandwiches are bread with a piece of meat inserted, yes

@DavidZ Plus a variety of other ingredients!

5:50 PM

Yeah, in this case mozarella sticks, fries, cheese, and hot sauce, if I'm not forgetting anything

@ACuriousMind is the hack stable?

@0celo7 As stable as modded Skyrom can be, I guess

@ACuriousMind So cripplingly unstable compared to normal games?

Not cripplingly, I'd say

I can't even load my Skyrim under 5 tries anymore :/

6:01 PM

I think it crashes like once every two hours

If mine doesn't crash on boot up I'm happy lol

@0celo7 Well, with "modded Skyrim" I didn't mean whatever Frankenstein setup you've created! :D

@ACuriousMind i've learned that removing mods actually breaks things more

do you remember my modding frenzy last year

@0celo7 I do

6:18 PM

@ACuriousMind Well now no one in Skyrim has underwear, dragons are basically invincible, and my Skyre patches failed so all of my weapons have vanilla stats but enemies have Skyre stats

weapons & armor

I don't know if women's clothes still work properly

I doubt it

user54412

7:01 PM

@DavidZ Sounds familiar :)

user54412

Off-topic: Nice alias! — 1010011010 22 hours ago

user54412

... says 1010011010 to 101010111100

7:25 PM

@EmilioPisanty: that's a really good answer :-) Why my answer has got so many upvotes escapes me. I suspect the dead hand of the hot questions list.

user54412

::whistles::

user54412

@JohnRennie Would you like a downvote instead? ;)

user54412

btw, does anyone else do this? Whenever I vote on a post, I make sure to read everything on the page and vote on all as necessary, independent of each other.

user54412

I feel a lot of people will only upvote at most one answer (the "best").

@DavidZ Hmmmm, no wonder people are getting more and more obese.

7:59 PM

@JohnRennie I suspect it made HNQ too

Yet another day of mild frustration at not having a clear list of what did and didn't make HNQ to audit

I was just going to comment with a link to the APS Physics summary.

But I got so incensed at the terribleness of the Science Alert stuff it just burst out.

8:29 PM

> The first I am considering is algebra, combinatorics, and topology (aka abstract algebra).

Academia SE be crazy

9:29 PM

@0celo7 algebra is better than geometry ;-P

@yuggib just stop

10:10 PM

@ChrisWhite I find that whenever I say "All I want to do is ..." about something LaTeXy, it will either be almost trivial, unreasonably difficult, or require me to add a major new package to my header (and keep a 100+ page PDF open to figure out how to use it).

Arbitrary positioning of things goes against some basic assumptions made by the usual classes, and so is hard without invoking special tools.

I've mostly found ways to work-around the limitation, rather than tried to learn how to do the thing I originally wanted to do.

LaTeX is just terrible

And still better than the alternatives.

Why can't it be user friendly

Part of the serious answer is that users want to do stuff without stopping to think about it's place in the larger scheme of the document, and LaTeX assumes you will specify structure, not details, while it takes care of the little decisions.

You can actually make Word do that kind of thing for you too, but those features also require careful thinking.

Heya

10:20 PM

@BernardMeurer At the saw again

10:32 PM

Welp, I look over at my thingie and the sample has disappeared

@dmckee I'll second @ChrisWhite's sentiment.

having said which, I think I've done about fifty thesis pages without physically yelling at LaTeX, which I think is probably a record.

@0celo7 Do you want to pay me the 20 bucks you owe me?

@EmilioPisanty grats :D But just imagine your supervisor asking you to write in Word when you need to yell the next time ...

@BernardMeurer What?

@Sanya Typed a paper in Word today

Was glorious

@0celo7 You owe me from the Bob bet; You're paying; When are you seeing Ron?

10:45 PM

@Sanya No such thing for me. Haven't touched Word for anything scientific since my first lab report in 2007.

@EmilioPisanty I never did so willingly either ...

@BernardMeurer What about Ron?

I don't know, Thanksgiving?

Why am I paying???

user218912

11:29 PM

@0celo7 how can I become better at proofs?

user218912

does it require me to practice doing them? 0.o

ask in the math chat.

user218912

fine...

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