The h Bar

Danu

16:00

@Secret It sounds rather like trying to attribute some ontological value to superpositions, which I would try to refrain from doing.

Secret

(The picture is being described in the form of words)
using this one can write out something like:

$$|m_{\nu}\rangle=\alpha |1\rangle+\beta |2\rangle+\gamma |3\rangle$$

David Z

Chat session time! I see we already have a conversation or two going

Danu

@DavidZ Tell us what to discuss, oh great leader!

John Rennie

Have we had another sockpuppetry outbreak?

Secret

@danu so you mean the actual picture of the superposition is not really various portions of the mass eignestates 1,2,3 contributed to the mass state vector?

John Rennie

16:02

I lost a load of rep yesterday.

Danu

@JohnRennie I lost some on History of Science and Mathematics, but not on Physics

@Secret I'm saying that you shouldn't try to ascribe any kind of "reality" to a superposition

(this is a philosophical position)

David Z

@Danu lazy :-P

@JohnRennie oh yeah, I think we deleted a few accounts yesterday... there always seems to be a sockpuppetry outbreak at some level

ACuriousMind

@JohnRennie You call 35 rep "a load"?

John Rennie

@Danu I lost 177 points!. Curiously, a large part of that was due to questions deleted by community. So it wasn't justb reverted upvotes.

David Z

We could discuss the Nobel prize.

The 2015 #NobelPrize in Physics is awarded “for the discovery of neutrino oscillations, which shows that neutrinos have mass”.

Tweeted by NobelPrize on October 6, 2015 at 9:50 AM

Danu

16:05

@DavidZ Ya lazy bastard! I already brought that up :P

ACuriousMind

@JohnRennie Huh, where did you get the 177 from? Your rep history shows only 35 due to user deletion.

Danu

@ACuriousMind Hullo

Secret

@danu ok noted I guess I'll stick to your matrix diagonalisation thinking direction then

ACuriousMind

@Danu Heyhey

Man, I'm not on for half a day, and my SE inbox is overflowing.

Danu

Only 10 more pages 'till the end of my notes! :D

David Z

16:06

@Danu yeah but not during the chat session

John Rennie

@ACuriousMind for example this question got deleted:

physics.stackexchange.com/questions/208218/…

Alizter

How does the book General Relativity without calculus make sense if it relies on the notion of tensor calculus?

David Z

Actually, we do also have this to discuss:

John Rennie

and I lost 50 points there

David Z

10

Q: Book recommendations: On-topic, on-topic but community wiki, or off-topic?

Yes, we've had this debate before. Unfortunately, there's no definite consensus to be found about their community wiki status: Good list, bad list (from July 2013) has the top voted answer (with a meager +11/-2) saying that book recommendation questions need to be actively moderated by the comm...

ACuriousMind

16:06

@JohnRennie Ah, I see

I thought questions with positively scored answers usually aren't deleted?

John Rennie

It was deleted by community, but I don't think it qualified for auto-deletion so I assume a mod intervened.

ACuriousMind

@DavidZ I'm a bit disappointed by the low overall votes there.

Secret

David Z

@ACuriousMind yeah, me too, which is why I featured it. Though there seems to be a consensus of sorts now

Secret

The maths looks ok
However it sometimes make me wonder how physicists can work out whether some interpretations are sensible while others are nonsensical

Fo example, in the wiki page, the paragraph describes the process that is happening. This is an interpretation because otherwise all you have is just the unitary matrices relating the mass and flavour eigenstates

ACuriousMind

16:11

@Slereah I've mused about that before - since the little group of massless particles is this weird ISO(2) thingy, and not SU(2), they are not transforming in a proper representation of the spin group. You can already see this because the photon is "spin-1", but has only two and not three distinct states, as the spin-1 rep of SU(2) would.

@DavidZ I'm not sure +9/-2 is a consensus, but it is definitely an option slightly preferred by the community, apparently. ;)

David Z

@JohnRennie yeah, with upvoted answers it wouldn't have been automatically deleted. That one you can tell from the fact that the user account is gone; it was probably an account that was deleted for posting low-quality content or spam

John Rennie

@DavidZ would that have deleted questions posted by the deleted account? I would have thought not.

David Z

@ACuriousMind I'm looking more at the score relative to the other answers, because the answers do kind of give a comprehensive listing of choices. +7 is significantly above +1. I'm disappointed because it's the one answer I strongly disagree with, but the community seems to favor it.

@JohnRennie depends on the circumstances of deletion.

Mike Edenfield

@JohnRennie I think it depends on the account and how much "activity" they have.

if it would be really disruptive to everyone else (lots of lost rep) then I think they just anonymize the questions.

David Z

Yeah, generally we try to orchestrate deletions not to get rid of good content. But perhaps we (I mean, whichever mod was involved) might have looked at the question score but not at the answers. I suppose we could undelete the question if it's really worth keeping.

Secret

16:15

@Acuriousmind @danu @JohnRennie @DavidZ That is, how does one check whether they understood correctly the physics from the maths and not just making nonsensical premises (like the common mistake of me ascribing a reality to the superposition, how to avoid similar wrong thoughts like these when I try to understand the maths I am deriving when working through the texts)?

Secret

I ask this question shows how bad my physical intuition is and how I oftne rely on the maths to understand a physics phenomenon

David Z

@Secret oh, sorry, I haven't really been following - but professional physicists argue about this a lot, so I'm not sure there is really a proper answer :-P

Secret

I just found I am being constantly point out wrong thoughts when I try to understand what the maths is telling me when doing quantum mechanics problems and reading material

John Rennie

Are we (collectively) worried that book recommendation questions will become a serious problem if uncontrolled?

ACuriousMind

@Secret That is why I subscribe to a kind of "shut up and calculate" attitude which largely avoids ascribing reality to anything but the predicted expectation values/uncertainties.

Danu

16:19

@DavidZ It's a difficult situation

I really want to have resource recommendation questions on the site, simply because I've had really good use for them in the past

ACuriousMind

@JohnRennie They aren't really about physics. That's why I feel they should be either community wiki so you don't derive rep on Physics from it, or off-topic altogether.

Danu

especially on the mathematics sites, but that doesn't really matter

I agree that maybe, in principle, they should be off-topic, but I think they're just too useful.

David Z

@Danu yeah, I'd just rather see that info in the tag wikis

John Rennie

It seems to me that the Physics SE is increasingly becoming an educational resource.

Secret

@ACuriousMind I do sometimes took that approach, and the result is pages and pages of algebra that nobody want to read

As demonstrated here in my past quantum assignment
https://i.sstatic.net/Uurga.png

And then my peers said I am losing track of reality

I think I need to read some text (if any) to understand the correct mindset to do physics, because currently my mind is either too visual, or too mathematical

Danu

16:21

@JohnRennie I'm definitely not.

John Rennie

We can't really claim it's a research community.

Danu

@JohnRennie Could we ever, really?

John Rennie

@Danu maybe in the early days.

But if we embrace the educational aspect wouldn't that make book recommendations an important part of what we do?

Danu

@Secret I think there is no easy way to get good at that kind of stuff, it mostly takes exposure to different points of view on (sometimes rather philosophical) issues.

@JohnRennie The point ACM already raised is also my main concern: It's not a question about physics.

I do think they're nice and important to have around, though.

@DavidZ That's just too obscure to be useful to most users

Also a lot of effort to set up & maintain, I think.

John Rennie

I find I'm increasingly uncertain about what constitutes a question about physics

ACuriousMind

16:24

I don't think I have ever read a tag wiki.

Danu

@ACuriousMind Exactly

ACuriousMind

Except for obscure tags to see what they're about, and then there mostly was no wiki to begin with :/

Danu

Let me give an example of why I think these questions can be very good

Which also demonstrates it's not always feasible to implement your idea @DavidZ

David Z

@ACuriousMind how often have you read a book recommendation question?

Danu

121

A: Best Algebraic Geometry text book? (other than Hartshorne)

I think Algebraic Geometry is too broad a subject to choose only one book. Maybe if one is a beginner then a clear introductory book is enough or if algebraic geometry is not ones major field of study then a self-contained reference dealing with the important topics thoroughly is enough. But Alge...

@DavidZ I have on at least 25 occasions

I think I went through all of the ones in our "most duplicated" book recommendation main question.

ACuriousMind

16:26

@DavidZ Several times because they kept coming up in searches instead of the actual thing I was looking for :P

Danu

The answer I think is really valuable, IMO.

^what a crappy sentence

Let me try that again

The answer I linked* is really valuable, IMO

And there is no way that that's suitable for a tag wiki

David Z

IMO that's exactly the kind of information that should be in a tag wiki. Like, you could copy and paste it.

ACuriousMind

@Danu True, that one is good. Then look at all the other answers to that question - that's why I want community wiki.

Danu

@DavidZ That big?!

David Z

Yes, absolutely!

0celo7

16:28

hello

Danu

@ACuriousMind Of course, definitely CW

@DavidZ Okay, then we have very different opinions on what tag wikis should be like :P

ACuriousMind

@Danu The wiki is distinct from the small popup that appears when you hover your mouse over a tag

Danu

I did not intend for them to be more extensive than wikipedia pages

ACuriousMind

(Just to make sure)

David Z

The tag wiki would also include other information, of course, but the content of the answer you linked would make a fantastic book recommendation section

Danu

16:29

@ACuriousMind I know that (I'm mod on a site, remember? ;D)

ACuriousMind

@Danu okay dont ban me

Danu

@ACuriousMind INCOMIIIING

I wish there was a "poke"-type ban (like 10 seconds or so)

(not really)

0celo7

I'd get poked daily

David Z

@Danu here's a decent one: the PHP tag wiki on SO

0celo7

out of the blue poking

ACuriousMind

16:30

@Danu That'd be too much power for you corrupt lot ;)

0celo7

good job astronomer

Danu

@DavidZ That's very different from the book recommendation thing; It's mostly links.

0celo7

that's the kind of stuff you should star

Danu

Ah, I finally understood why you keep on talking about "astronomer"

0celo7

YOU'RE THE ASTRONOMER

David Z

16:32

@Danu a lot of the links go to documentation and tutorials. For software, those are your resource recommendations.

0celo7

I only talk about him when he's around...

Danu

@0celo7 Everybody is the astronomer

0celo7

so you must be him

Danu

And no, I did not star those messages :P

0celo7

who could it be

I wish stars were public record

Danu

16:33

@DavidZ Well fine, but I think that that's a bit of a cop-out then. Links to external, more extensive, sources of information is good usage of tag wiki space IMO, but long descriptions of books is not.

So in this case it may work out well, but that does not imply that the analogous thing for math works (to me, it does not).

0celo7

FWIW, I agree with David

David Z

Those are not long descriptions of books, though - at least, I wouldn't consider them long.

0celo7

@Slereah that is a good theorem

David Z

But regardless of how you characterize them, I think the kinds of descriptions in your linked answer from MO would fit perfectly into a tag wiki

Danu

@DavidZ I agree (I hesitated when typing that), I meant to say that the whole thing is very long.

0celo7

16:35

@yuggib yes

Danu

@DavidZ Okay, I guess we should agree to disagree :)

David Z

I guess so

0celo7

but one of the disagreers is a mod so he wins :)

ACuriousMind

@0celo7 They're both mods, silly

Danu

@0celo7 Fail :P

David Z

16:36

lol :-P

0celo7

::sigh::

but one of the disagreers is a mod on a site that matters so he wins :)

I thought that was implied...

David Z

@0celo7 but seriously though, that's not the way it works. Not when setting policy.

I guess it's not unprecedented that the moderators of a site say "it has to be this way, we're invoking the 'mod override' option", but we generally don't do that

0celo7

I know, it was a joke

David Z

you never know who will properly take things as a joke on the internet

Danu

@0celo7 No

Physics has some (marginal) importance too, in the SE network ;)

0celo7

16:38

@Danu no what?

OH

rekt

Math is the most important

ACuriousMind

@Danu I was wondering when you would make a retort to that effect :P

0celo7

the average GPA of math students would drop were it not a thing

obe

lol

Addem

I think on a Physics forum the decision procedure for whether a given person will get a joke is a lot simpler: No.

Joking!

Danu

@ACuriousMind I can always be counted on to be... snappy? :D

ACuriousMind

16:40

@Addem I don't get it.

0celo7

Why are people passing out New Testaments on campus

most people have bibles

and those that don't don't want them

David Z

@Addem as a first approximation, that's probably not bad :-P

Addem

:)

Danu

@ACuriousMind It's that physicists have sh!t humor :)

0celo7

Germans

John Rennie

16:41

@0celo7 due to the recession students can no longer afford fuel

Danu

@0celo7 Poor old (or rather, young!) America

@JohnRennie :D :D :D

ACuriousMind

@0celo7 ::looks around:: Where are they?

@Danu Oh.

0celo7

@JohnRennie don't get it

Danu

@0celo7 New Testament is meant to burn

ACuriousMind

@0celo7 You need to keep warm in winter, don't you?

0celo7

16:42

wow

ACuriousMind

Our star wall is a mess :P

Danu

I think chat is kill

David Z

Just don't star fluff

Danu

Meh, I don't actually care much about what is on the starred-wall.

It's something like the HNQ's

David Z

I've kind of taken a hands-off attitude toward the star wall - I figure, if y'all want to see better stuff up there, you should be more discerning in what you star

We don't really have that many important messages anyway

ACuriousMind

16:48

@Danu Ouch :D

Danu

@DavidZ Exactly. What kind of useful information does anyone expect to extract from it? :P

0

Q: What happens if locally manifold is seen as an Euclidean space?

I have been trying to understand the definition of a manifold and I have found out that the most common definition (even around here on S.E.) is: A manifold is a space that has a complicated "topology" globally but "locally" can be considered as an Euclidean space. So, what is the advantage (if...

general-relativity differential-geometry topology

Off-topic, right?

ACuriousMind

@Danu Agreed.

David Z

@Danu Well, it's meant for messages that are likely to be useful to other people entering the room later. So, I bet there are a few messages from our discussion on book recommendations that would be worth starring.

Secret

Should be migrated to MSE

that's pretty much a maths question

David Z

The idea is that someone can come into the room, glance at the star wall, and get a quick summary of what's been discussed recently

ACuriousMind

16:51

@DavidZ ...I think we've never treated the star wall like that

John Rennie

@ACuriousMind is that off topic?

Danu

@DavidZ I think that this intent was lost long ago in all major sites.

@JohnRennie You don't agree?

John Rennie

Isn't all of physics reliant on the universe being a differentiable manifold?

David Z

@Danu cc @ACuriousMind oh, of course

Danu

@JohnRennie Note that the question doesn't even mention physical context.

Also it's just too broad IMO

John Rennie

16:52

Ok, so that's your cue to provide the physical context in an answer

It is broad though, I agree

ACuriousMind

@JohnRennie It asks why a manifold is defined as something that's locally R^n. I see not much physics content in that.

Danu

@JohnRennie I think that the physical reason is not what the OP is after

The OP is asking "why would we want to consider things that are locally like $\mathbb{R}^n$?"

I outlined a possible answer in my comment

John Rennie

@Danu and the OP likes it!

Danu

Other possible answers could include (1) because it's broad enough to incorporate a lot of stuff we see in the real world (2) because it's the most natural realization of $\mathbb{R}^n$ etc.

@JohnRennie Well, good for me and him, I guess, but that doesn't mean that the question is on-topic :P

(I do feel tempted to answer it, but I think it should be migrated first)

John Rennie

I can't help feeling we have something of a culture of aggressively closing questions.

And I concede I play my part in that.

Danu

16:55

@JohnRennie In this case there was nothing aggressive about it

I really think I was a nice guy here :P

I gave reading recommendations, explanation for VTC and also a short answer.

ACuriousMind

@JohnRennie Closing questions is really the only quality control apart from normal voting that we have.

John Rennie

@ACuriousMind I'm not longer sure what our quality standards are.

Apart from the obvious homework/lazy questions

Danu

@JohnRennie I think that, to some extent, it's a personal question.

David Z

@Danu why both answer and VTC? Those are at cross purposes

Danu

@DavidZ I didn't post an answer!

John Rennie

16:57

@DavidZ The answer was a comment

Danu

I gave an answer in a comment.

John Rennie

I sometimes VTC then give a partial answer or a hint comment to prove I'm not a complete bastard :-)

Danu

@JohnRennie I do feel like you're constantly feeling guilty/bad about closing/downvoting question.

David Z

@Danu oh. Uh... don't do that either :-P but I see what you were saying

Danu

Why is that? They're just asking you to spend your time on their problems. Why do you feel so obliged?

David Z

16:59

@JohnRennie how so?

Danu

@DavidZ I don't think that's bad practice.

John Rennie

@DavidZ because I'm no longer sure what we're trying to achieve.

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