The h Bar

Balarka Sen

4:00 PM

I guess you're mostly an analyst?

0celo7

Yeah

Balarka Sen

Gotcha

Slereah

is the non-metrizability of non-Hausdorff manifolds connected to the fact that, if two distinct points share the neighbourhoods, their distance will always be 0?

I don't know if that's true but it sounds reasonable

0celo7

@Slereah Any metric space is Hausdorff

Balarka Sen

@Slereah Metric spaces are Hausdorff. You can make the neighborhoods small enough because you can make the diameter small enough

Slereah

4:01 PM

@0celo7 But what about the converse

Oh wait

0celo7

Definitely not

Balarka Sen

True modulo second countability

Slereah

nvm

ACuriousMind

Welcome to the chat session! Please keep unrelated discussion out of the room until it ends.

Balarka Sen

Second countable Hausdorff spaces are metrizable

ACuriousMind

4:01 PM

Today's agenda:

1. Welcome, introduction, general questions
2. Recent events in physics (5-10 min, depending on interest)
3. [Chat moderation and politics](http://meta.physics.stackexchange.com/q/9596/50583), see also [meta chat](http://chat.stackexchange.com/rooms/13775/physics-meta) (open ended)
(4. Renaming the room?)

Oh well, damn formaitting bug, but I guess it'll have to do.

So, anyone new to the site, the chat, or chat sessions?

0celo7

@ACuriousMind I'm new

I just got here 2 days ago

Slereah

My friend @0celo7 is all new

ACuriousMind

→ 4 messages moved to Trash

Slereah

Give him a warm welcome

AnimatedPhysics

I am new

Slereah

4:03 PM

@ACuriousMind has an itchy trigger finger lately

Balarka Sen

@ACM Did you seriously invite me to trash. Anyway, yeah, sorry for off-topic.

ACuriousMind

@Slereah It's always been itchy during sessions, it's just usually DavidZ doing this

@AnimatedPhysics Hi there!

AccidentalFourierTransform

Hi @AnimatedPhysics, welcome. Please say your name, address and ssn. Thanks.

0celo7

@ACuriousMind Do I seriously not get a welcome?

ACuriousMind

@0celo7 Welcome :P

0celo7

4:05 PM

@AccidentalFourierTransform Revolver J. 0celo7, 1600 Pennsylvania Ave, 137-69-1337

Slereah

A good social security number

0celo7

@ACuriousMind Don't be a stranger

ACuriousMind

So, if anyone has general questions about the site they'd like to discuss/get an answer to, now is the time, otherwise we'll go on to what caught your eye recently in physics

0celo7

I want to MPSEGA

AccidentalFourierTransform

something something build a wall

0celo7

4:07 PM

To keep the trolls out, yes

AnimatedPhysics

Physicists address loophole in tests of Bell's inequality using 600-year-old starlight phy.so/405674843 Thoughts?

Slereah

Trump will close all the tax code's loopholes for Bell's inequality

Balarka Sen

@0celo7 And make themselves pay for it?

0celo7

@BalarkaSen Well now, I don't want to be called a racist.

AndyD273

I'm new. I saw the announcement over in WB chat, figured I'd see what was going on

ACuriousMind

4:09 PM

@AnimatedPhysics That does look interesting! Closing the loopholes is always good since some people still hope for one of them to actually disprove QM

0celo7

But all my friends at the KKK say this is a good plan. They are smart people you know!

ACuriousMind

@AndyD273 There's an announcement in WB chat? I didn't know that, but welcome nevertheless!

AndyD273

@0celo7 They spell clan with a K. Your argument is invalid.

@ACuriousMind It just popped up at the top of the screen. I don't know why...

Slereah

@ACuriousMind I think you mean the COPENHAGEN INTERPRETATION

You rude person

0celo7

@AndyD273 It's a stylistic choice.

ACuriousMind

4:11 PM

@Slereah Hm? Is Bell's theorem dependent on the interpretation?

@0celo7 @AndyD273 Please don't continue discussion of the KKK here, thanks.

Slereah

Yes

Balarka Sen

May I know what Bell's theorem says?

Slereah

The Bell's inequality holds for Kolmogorovian theories

Of which the copenhagen interpretation of QM isn't one

John Rennie

→ 2 messages moved to Trash

AnimatedPhysics

@ACuriousMind i dont know if the hope is to disprove. Seems how qm works is pretty well proved. It would be nice to see a more understandable explainatiion or model.

0celo7

4:14 PM

@BalarkaSen Quantum mechanics cannot be explained by hidden variables, basically.

Balarka Sen

What's a hidden variable?

ACuriousMind

@BalarkaSen It's a statement that bounds certain values of theories of local hidden variables, and the bound is violated by quantum mechanics, so showing the inequality holds is a way to show that we cannot explain quantum mechanics by such theores

@AnimatedPhysics Sure, the people doing the experiment aren't hoping to disprove, but the more evidence for the violation of Bell's inequality we accumulate, the harder it gets for those who still hope there's hidden variables

AnimatedPhysics

Hidden variables of bell require determined reaults to work. They aasume nondeterminiatic models will not work.

0celo7

@BalarkaSen What I hope to work on this summer. Mods, that will be my last interruption.

ACuriousMind

@BalarkaSen Essentially a theory that declares that all the results of measurement exist prior to measurement, contrary to the standard interpretation of QM where the results only exist as a probability distribution prior to measurement.

Secret

4:17 PM

What's the current status for nonlocal correlations that are stronger than entanglement, i.e. those related to the nonlocal box thought experiment in quantum?

Balarka Sen

@ACuriousMind Ah, that makes sense.

ACuriousMind

@Secret No idea, do you have a link for what experiment you're thinking of?

Secret

I suspect I might be referring to Superquantum nonlocality that I briefly read in wikipedia some months ago

0celo7

Superquantum?

AnimatedPhysics

@ACuriousMind well put.

0celo7

4:20 PM

Can I just stick "super" on my thing and get funding?

Slereah

Superhilbert space

ACuriousMind

Anyway, time for this step is running short (but feel free to resume discussion of Bell's theorem or anything else mentioned after the session!). We should move on to the probably most contentious point, chat moderation. For context, see this meta post, its comments and its answers.

Slereah

Supermanifold

0celo7

Supercurvature flow

HDE 226868

@AndyD273 Did you register for the chat session? That should trigger it, I believe.

Slereah

4:21 PM

@ACuriousMind down with the tyrants I say

3

0celo7

Superheat equation

AndyD273

@HDE226868 I don't think so? If I did I'm not sure when anyway

ACuriousMind

@Slereah Yes, that appears to be a common sentiment. ;) Alas, there are no tyrants here, at least we like to think so, which is why were having this discussion.

Slereah

sayeth the tyrant

Balarka Sen

@ACuriousMind I vote for being a little more lenient on moving things to trash!

4

ACuriousMind

4:24 PM

@BalarkaSen Are you referring to the things referenced in the meta post or to moving things unrelated to the session out of here?

Balarka Sen

the crowd here is wilder in nature than my home chat tho

@ACuriousMind I don't know, but as an outsider I feel like the moderators here is far more tough and strict and all than where I come from

(math chat)

Secret

h bar is not restricted to physics topic and maths chat only adopt this pathway rather recently, thus it is not surprising the crowd is wilder here

ACuriousMind

Anyway, first, let me say that the criticisms of poor communication are justified. The moderators (in particular me) started to enforce a rule (that we didn't feel would be so contentious, honestly) without sufficient prior discourse on meta. That was a bad move to make and I apologize for it.

Balarka Sen

I respect the decisions made by the moderators, though, so take that as an observation than a critique.

0celo7

Which rule is that?

The politics or the one that caused the massacre the other day?

ACuriousMind

4:27 PM

@0celo7 The "don't talk politics" one. I'm not sure which other one you're referring to?

DanielSank

are we still in chat session?

Secret

we are

0celo7

@ACuriousMind The other day @DanielSank and @rob moved probably 100+ messages to the physics meta

That should be @DavidZ

Dr. Sank is mostly innocent

AnimatedPhysics

The first respose to my post was for trump to close the loophole. Sounds like politics not physics.

DanielSank

@0celo7 Y U NO EDIT?

0celo7

4:29 PM

@DanielSank Don't know how.

DanielSank

If you try for 20 seconds I bet you will succeed.

David Z

@0celo7 you should fix that

AnimatedPhysics

But i dont mind. Thought it was funny.

ACuriousMind

However, let me also say that this wasn't borne of nothing. On an SE wide level, both this and this post were triggered by significant unrest caused in other chatrooms that went far beyond mere profanity not "not being nice".

5

0celo7

@DavidZ How do I find out?

Secret

4:30 PM

My thoughts about politics is that it is always very prone to degenerate into flame wars, but it seems in recent years political discussions in many sectors of the internet escalates easily to flame wars possibly due to the trump politics news and stuff (and researches showing that the political divide is getting worse). Like one of the meta answers, however it is unclear how one can ban politics, as it is indeed a rather huge field

DanielSank

@ACuriousMind As we have already discussed, at considerable length, the problem is not what we are trying to do, it's that banning "politics" is incredibly unclear.

Shall we have the same discussion again, or shall I link to our conversation from yesterday for everyone here's convenience?

David Z

@0celo7 huh, I'm surprised not to find a guide. Well, I'll let you know later since we are in the middle of something.

ACuriousMind

@DanielSank Yes, it is. That's because human communication is fluid and does not lend itself well to rules that can be mechanically applied. Yes, "politics" is incredibly unclear, but so is "be nice". Both of these guidelines (yes, guidelines, we're not making codified law here) expect all participants to respect the spirit of the rule, not the letter.

Making mechanically strict rules often leads to rules-lawyering trying to find loopholes, which leads to making the rules more complicated (but specific), until you end up with a long list of very specific things that no one has any full grasp of anymore.

Ramanujan

How about suspending user for not following rules?

DanielSank

@ACuriousMind What is the "spirit" of "no politics"?

Slereah

4:35 PM

It is a ghost

DanielSank

I understand the spirit of "be nice". I do not understand the spirit of "no politics".

Balarka Sen

@Ramanujan That goes very badly in general

ACuriousMind

> Note that this ban on political discussion is of course subject to common sense, and subordinate to its goal of prohibiting inflammatory discussion. You will not be banned for mentioning the newest EU regulation on cucumber curvature, or curiously asking what political structure another country has, etc. It should be pretty evident in most cases whether a given topic has the potential to be inflammatory or not - if in doubt, make another room for it or just ask. Even if I have repeatedly stressed that the ultimate power lies with the moderators and room owners, this does not mean you shou…

0celo7

@DavidZ Is it hard?

DanielSank

@ACuriousMind Are you ignoring the entire discussion we had yesterday on purpose because you want to redo it here?

Secret

4:36 PM

I think for starters, given all that data in SE in the recent two years, "no politics" at least means no mention of trump stuff (cause that seemed to be the easiest to escalate)

Balarka Sen

@DanielSank There's a unspoken understanding in, eg, the mathematics chat so that if a political discussion comes up, it's either harmless or someone just asks to drop it at some point and we drop it.

I think the analogous user-equilibrium lacks here

DanielSank

@BalarkaSen The problem is that we don't agree on what "politics" means. DZ, ACM, and I discussed this yesterday in the meta chat.

Just a moment. I will find the discussion from yesterday.

Balarka Sen

But surely you agree on when a political discussion comes close to being inflammatory?

ACuriousMind

@DanielSank It's linked in an answer to the meta post

Secret

Balarka: Indeed, we do have some heated folks here, thus the equlibrium is rather lacking

Balarka Sen

4:38 PM

The issue is not talking politics, but avoiding having a flame-war. I am sure we understand that much?

DanielSank

@BalarkaSen I agree when a discussion is inflammatory, but I refuse to comment on "political" discussion until we agree on what "political" means.

ACuriousMind

@Ramanujan Yes, that's another point that has come up. The concern here is that while banning people after the fact is punishment, it doesn't undo what has already transpired. As I already said, politics has shown to provoke unpleasant events that are not mere profanity or small disagreement but significantly upset the peace.

DanielSank

@BalarkaSen Obviously. Unfortunately, our present policy doesn't say that. It says "no politics".

Balarka Sen

Well, that's definitely vague and unreasonable.

Someone is sure to come up with something political once in a while because our world is a political shitstorm right now

The goal should be to not make that into a war

ACuriousMind

It seems to me that the general tone of this chat room is saying that they're willing to take that risk. If that's what y'all want, then I think we could try it. But I fear the risk is greater than most of you imagine because you haven't been privy to what has transpired on other sites (which is not really public because it has been mostly contained and deleted).

AccidentalFourierTransform

4:41 PM

@ACuriousMind so I guess that's pretty much your answer to this, right?

DanielSank

@ACuriousMind Here are the problems in order of most to least important:

AccidentalFourierTransform

(it's a valid answer BTW; maybe Im too naive)

ACuriousMind

@DanielSank I reread the transcript today and yes, you keep saying that the policy is just "no politics". But it's not what the policy is intended to say. It's a plea to try to avoid political discussion in general and I explicitly included some (admittedly purposefully silly) examples to show that there will be no repercussions for trying to discuss a harmless political topic.

AnimatedPhysics

I like "no politics" as default. Go easy from time to time on jokes and non-inflamitory stuff but no politocs as default.

DanielSank

1) The present ban uses language that is confusing to a lot of us. As we discussed, at length, yesterday, "politics" means something very different to e.g. @DavidZ than it did in my mind and heather's mind. 2) Some people want to try a lighter touch, and use a stronger one if needed.

@ACuriousMind Did you read the part of the transcript where @DavidZ and I realized that "political" means something much more specific to him than what heather and I had in mind?

ACuriousMind

4:44 PM

Maybe it's the tone of the meta post, maybe it's that it's coming from a moderator, but it's not intended to be a draconian ban that gets you tarred and feathered for daring to mention something that might be construed as a political argument. It's a guideline, just like the Be Nice policy doesn't mean you'll get instabanned for a single instance of profanity but nevertheless generally urges users to not be profane.

DanielSank

in Physics Meta, 18 hours ago, by David Z

@DanielSank It's barely political, to my knowledge. I don't know what else to tell you. It's just a law.

^ That suggests:

1) To DZ, talking about laws is not "politics". That is probably not what most users think when then hear "politics".

2) Under a "no politics" rule/suggestion/whatever, we can still talk about laws, which I think is probably not even the intended behavior under the new rule.

The point is (and it's the same point I keep making about the homework policy), the written rules are confusing.

Saying "use common sense" is not a replacement for un-confusifying the rules!

AnimatedPhysics

Laws are politics. Physics is theories and experiments.

ACuriousMind

@AccidentalFourierTransform Yes. As I said, if people keep saying that they'd rather take that risk than have a general agreement to try to avoid politics, then I guess that's fine by us. Disaster is not inevitable, it just seems so likely that we thought we'd be proactive. That's a subjective judgement and I'm willing to let it be overruled.

DanielSank

@AnimatedPhysics See, you straight up disagree with DZ.

AccidentalFourierTransform

@ACuriousMind see, it's not like the Be Nice policy. We all agree that insulting someone is wrong, even if it might be tolerated from time to time, depending on the context. But most of us will not agree that talking about Trump is a bad thing, even if you also propose that it might be tolerated from time to time, depending on the context.

the Be Nice policy and the No Politics policy are very different, because most of us dont think that politics is wrong, while we all do agree that not being nice is wrong

DanielSank

4:51 PM

^ Agreed

AndyD273

So, since I'm new here... What are we talking about exactly?

DanielSank

...but i still want to know what "politics" means.

@AndyD273 There was recently a decision to ban, or strongly discourage, discussion of politics in this chat room.

David Z

@AndyD273 We're discussing whether to impose a ban on discussion about politics (or a subset thereof) in this room

AndyD273

Ah, I thought it was going to be a physics talk today. OK, just wanted to check.

ACuriousMind

@DanielSank I think you find the rules confusing (and, more importantly, you think that's the most important issue to address) because you keep viewing them as laws rather than guidance. They aren't laws. They're delarations of intent in the sense of "in order to avoid inflammatory discussion, try to stay clear of political topics", not laws to be exacted impassionately.

I see that that has not been clear enough. If you don't think of "no politics" as a law that has to be enacted by third parties then the exact scope of the word "politics" becomes much less important than its intent.

DanielSank

4:53 PM

@ACuriousMind The homework policy is also "guidance", and you better believe I find it confusing too.

@ACuriousMind You know what's fascinating here: both heather and I expressed that the rule is confusing, and yet you're still arguing that it's our fault for not looking at the meta post with the right way.

ACuriousMind

@AccidentalFourierTransform Yes, I realize that. I didn't mean to say that their content is comparable, but their interpretation: Both are not black-and-white sets of rules whose violation immediately furnishes a specific outlined consequence.

0celo7

Still chat session?

ACuriousMind

@0celo7 6 mins to go

DanielSank

Maybe it's the post's fault for not being clear. Just a thought.

If you want to say "Daniel, "politics" is the best word we're going to come up with. We'll have to deal with that until someone suggests a better phrasing", then fine. But up and say that instead of blaming the confusion on the reader.

ACuriousMind

@DanielSank My "I see that that has not been clear enough. " is an admission of that. I'll think about how to make that more clear in the future, but currently I'm not sure there is agreement to try to refine the policy at all instead of dropping it.

0celo7

4:56 PM

@AccidentalFourierTransform We do not all agree that insulting someone is wrong.

Terry Bollinger

Hey oh all.

DanielSank

heyyoooo

AccidentalFourierTransform

@0celo7 I see you learnt how to edit ;-)

Terry Bollinger

Ah reads good too!

0celo7

I don't know what you're talking about

DanielSank

4:58 PM

@TerryBollinger eh?

HDE 226868

@0celo7 Please explain how insulting someone is not wrong, and does not run counter to half of Stack Exchange's chat policies.

Terry Bollinger

I think I replied to some other conversation!

ACuriousMind

Since we have received little to no truly positive feedback my impression is that the main attitude here is that we should not try to have such a guideline as "try to stay clear of politics", regardless of what "politics" exactly means. Unless this changes in the next day or so, I think the next step will be to mark the meta post as a failed experiment and return to solely enforcing the Be Nice policy as such

7

0celo7

@HDE226868 Burden of proof. You have to prove to me that it's "wrong," whatever that means. And I don't really care about the policy.

DanielSank

@ACuriousMind Perhaps.

@0celo7 False.

Terry Bollinger

4:59 PM

Hmm, we seem to have dived into a non-physics debate. Later all!

0celo7

@DanielSank You're false.

ACuriousMind

Alas, time's up for the chat session, thanks everyone for participating. You may return to your regularly scheduled non-scheduled conversations.

David Z

@ACuriousMind I'm kind of okay with that.

DanielSank

-_-

David Z

@ACuriousMind Don't forget "see you all in two weeks!" Those are the magic words that make the next chat session happen :-P

0celo7

5:01 PM

@BalarkaSen My advisor is giving me a book on geometric measure theory that I am to peruse

HDE 226868

@ACuriousMind I've been silently watching for most of this, and I think that that's the best idea. Part of the issue is that there is no direct evidence that points to an exact outcome if the chat room takes either of these options. Maybe in a week or two, we can look back and see where things succeeded and failed.

ACuriousMind

(You can of course also feel free to continue this conversation but I have to bow out since I also have a real world life, contrary to what it might sometimes seem like ;) )

Balarka Sen

@0celo7 Is it Federer's?

0celo7

@BalarkaSen No

Balarka Sen

whew

0celo7

5:02 PM

Why?

Balarka Sen

The general understanding is that it's unreadable

Anyway, GIT is good

Secret

Cannot wait when they deliver something interesting about equivalence principle, probably a first step towards QG

0celo7

@BalarkaSen Have you heard that from anyone other than Ted?

Balarka Sen

Yes

0celo7

Who?

Balarka Sen

5:03 PM

A couple of geometric group theorists.

0celo7

So algebraists

Balarka Sen

Huh? No

0celo7

I don't trust those people on anything

Balarka Sen

Geometric group theory is very not algebra.

Eg, most of them are also 3-manifold topologists.

0celo7

So topologists. I don't think I trust them either

In any case, Federer is too topological

The book he's giving me is completely analytical

Balarka Sen

5:05 PM

ic

gotta get dinner

0celo7

bye

Although I'm not sure when I will read it. I want to finish Hall, then read Wald's AQFT book (@Slereah ), then Yosida's functional analysis

Certainly not all of Yosida

Slereah

So

Non-hausdorff spaces aren't metrizable

But

are they pseudometrizable

0celo7

who even uses pseudometrics?

AccidentalFourierTransform

I pseudodo

0celo7

make metrics great again

AccidentalFourierTransform

5:08 PM

i.imgur.com/veP3ER0.gifv

0celo7

JOHN CENA

Slereah

I'm guessing that for a non-Hausdorff manifold, every coordinate patch is Hausdorff

0celo7

coordinate patches are homeomorphic to $\Bbb R^n$, hence Hausdorff

Slereah

since $R^n$ is

0celo7

yes

bolbteppa

5:11 PM

Ever come across 'spin weighted spherical harmonics'?

0celo7

yes

bolbteppa

What's the dealio with them

0celo7

don't remember

that was back in my physics days

before I met $\epsilon>0$

Slereah

What about $\epsilon <0$

0celo7

I've never seen that

is that nonstandard analysis?

Slereah

5:13 PM

No

it is a number smaller than zero

Called a "negative number"

0celo7

is that constructive?

Slereah

it is used in some algebraic equations of the type $a - b$, for $a < b$

0celo7

why is $(-1)^2=1$, anyway

bolbteppa

It's the degree of the magnetic quantum number of a spherical harmonic

$\varepsilon < 0$

Slereah

$(1 + -1) (1 + -1) = 0 \to (1 - 1 -1 + (-1) \cdot (-1)) = 0$

bolbteppa

5:16 PM

Basically just want to get degree $l/2$ representations from the Laplacian directly, and Penrose's popular science book references these beasts!

AccidentalFourierTransform

ok but what about $\tau=3.4$?

0celo7

idk why people still use $\pi$

$\tau$ is clearly superior

Slereah

Eh

$\tau$ is mildly more convenient

But it's not worth the hassle of changing all math to reflect it

0celo7

change all math?

abandon the old books

AccidentalFourierTransform

$$\sum x^i\phi^{\Delta^a}[Z]=[\Theta]''$$

0celo7

5:18 PM

they all violate basic logic anyway

@AccidentalFourierTransform this looks like QFT

AccidentalFourierTransform

Slereah

Well sure, but then are you gonna rewrite all the math books

Are you gonna rewrite every proof

AccidentalFourierTransform

@Slereah ive done that already

im hella smart

I bet I have more chromosomes than you

Slereah

Can you prove that $2+2 = 4$

David Z

@AccidentalFourierTransform that's... weird

AccidentalFourierTransform

5:21 PM

I have, at least, this many: ..................

maybe more

anonymous

@AccidentalFourierTransform Even potatoes have more chromosomes than humans :'D

AccidentalFourierTransform

that rude dude

anonymous

@AccidentalFourierTransform And this "I bet I have more chromosomes than you" isn't ?

I was just stating a fact. Biology fact !

0celo7

@Slereah yes

$2+2=2+s(1)=s(1)+s(1)=s(1+1)=s(2)=3$

wait

AccidentalFourierTransform

@anonymous I am allowed to be rude because I pay my weekly fee to the moderatos

Slereah

5:24 PM

WRONG

anonymous

@AccidentalFourierTransform So do I ;)

0celo7

$s(1)+s(1)=s(s(1+1))$

Secret

@AccidentalFourierTransform I wonder if this equation actually has a well defined meaning

0celo7

there

or $s^3(1)$

Qmechanic

0

Q: Improvement of Von Neumann's measurement scheme

I would like to know some opinions and references on possible improvements of Von Neumann's measurement scheme beyond the use of POVMs. Specifically, I am interested in the possibility of implementing a sort of post measurement state transformation generalizing the "collapse of wavefunction" whi...

Primarily opinion-based/unclear what you're asking?

David Z

5:25 PM

@Qmechanic POB, yeah, I think so. It even says so right in the first sentence of the post.

AccidentalFourierTransform

@Qmechanic I sincerely don't know what's being asked

Secret

That question can only survive as a list question, PSE cannot do Q and A

AccidentalFourierTransform

so both POB and unclear

Secret

The OP seemed to ask for opinion for a post measurement transformation scheme, and how the measurement process should be defined as (a dynamical evolution or a instantenous interactions like operators)

Slereah

archive.numdam.org/ARCHIVE/AIF/AIF_1963__13_2/…

That's one of the perks of speaking french

0celo7

5:33 PM

teach me your ways o wise frenchie

AccidentalFourierTransform

:: laughs in baguette ::

Slereah

"Any Lorentzian manifold which is timelike multiply connected has a diffeomorphic universal covering space which is timelike simply connected."

I'm too tired to deal with this shit

Secret

timelike multiply connected? Are we dealing with some lorentzian manifold which has many points being identified along the time direction...?

Slereah

It is just the homotopy of timelike curves

Secret

ok I see

DanielSank

5:54 PM

Hi, everybody.

user228700

6:44 PM

Hi :-)

user228700

Is the chat session today?

anonymous

Chat session is over

user228700

Ohh, OK.

Sir Cumference

Welp, I missed it :/

user228700

I don't understand anything anyway so no regrets :-P

Sir Cumference

6:46 PM

In other news, SO got a new experimental topbar

anonymous

See ACM's new message on the starboard

You'll get the gist

The one with 4 stars >

user228700

Alright, thanks.

Sir Cumference

Darn it, I really wanted to voice some opinions

Bernardo Meurer

@SirCumference Meta post is still open

5

Q: Chat and the moderation thereof

So, there has been considerable dissatisfaction with recent moderator actions in the h bar, physics.SE's main chat room, at least in part because people feel they have not been properly informed about the rules, policies, and consequences of violating them. We'd like to take the opportunity to co...

discussion policy chat moderation

anonymous

Honestly speaking, it was much ado about nothing ...!

However, I am happy that things are settled now

Wdoctor123

6:55 PM

Is there a test to see how linear the relationship between 2 data sets

?

anonymous

@Wdoctor123 There is a math topic called correlation and regression...

Wdoctor123

ok

and?

anonymous

You will find it on Wikipedia. Learn the method and apply it.

Wdoctor123

will it apply on graphs as well?

anonymous

It is specially for graphs

Wdoctor123

6:57 PM

So it will help me to find our how linear the graph is right?

out*

anonymous

math.arizona.edu/~jwatkins/c-regression.pdf

See for yourself.

Yes

@Wdoctor123

A more basic approach is here sphweb.bumc.bu.edu/otlt/mph-modules/bs/bs704_multivariable/…

Wdoctor123

thank you :)

does correl function in excel do that?

I was working on excel and I found this function

so just wondering if I can use it

anonymous

Yes it does

excel-easy.com/examples/correlation.html

Wdoctor123

thanks

Sir Cumference

Last night I had this weird dream where I was in a restaurant, but instead of food you got to order a solution to Einstein's field equations.

I think I might be a little too focused on school

Wdoctor123

7:13 PM

Well did you get the solution?

Sir Cumference

@Wdoctor123 I tried to order the FLRW metric, but @0celo was my waiter and refused to serve me until I went into the kitchen and proved I could make it myself

0celo7

because you don't even know what a metric is

Bernardo Meurer

Like a metric in an euclidean space?

Sir Cumference

@0celo7 My understanding is pretty bad, but I have a few key points about metric tensors in my notes.

obe

@SirCumference its ok read a gr book and it will make sense.

Sir Cumference

7:25 PM

@obe I'm trying, but it's hard as hell to get everything done in time

I'm not sure if I want to continue double majoring

obe

just let go dude, do whatever you want and dont stress yourself

take less courses if it makes you feel better

Sir Cumference

@obe I guess you're right...

Danu

@0celo7 Have you read Milnor's book on Morse theory?

0celo7

@Danu yes, but I'd say I understood only 3/4

Danu

in Mathematics, 2 mins ago, by Danu

@MikeMiller @BalarkaSen I will probably be participating in a seminar going through Milnor's book on Morse theory next semester. I may have to choose what part to present on tomorrow. What would you recommend?

0celo7

7:36 PM

@Danu give a detailed proof of theorem 3.4 and send it to me k thankz

That might not be the one I'm thinking about

@Danu There two main proofs of the book are not given in detail

At least not in enough detail that I was able to understand them.

Danu

Maybe just return to them sometime later.

0celo7

@Danu I probably won't, they're very algebraic topology heavy

They use homotopy of direct limits or something

(And I have no desire to learn algebraic topology right now)

@Danu Does it have to be from the book? Milner uses a finite dimensional approximation to the path space. I'd be interested in learning about the full thing.

Interesting autocorrect to Milnor there

Danu

Probably has to be from the book

Also I don't wanna spend all too much time on this

Though I might get carried away

anonymous

@SirCumference Since you are an astro student I wanted to ask you something that's been bugging me for some time. Do you know how to use reduced mass concept in gravitational two body problems, for example for binary star systems?

0celo7

8:09 PM

@Danu His proof of Cartan's theorem is pretty wicked

@Danu complete, simply connected, negatively curved implies diffeo to Rn

0celo7

9:02 PM

@SirCumference only a physicist calls it a "metric tensor"

not even a mathematical physicist calls it that

so only the worst kinds of physicists do

0celo7

9:19 PM

@Slereah $P^2/2m-X^4$ is not essentially self-adjoint on $\mathscr D(\Bbb R)$

quantum mechanics is broken

but apparently that system is really bad classically too

heather

9:34 PM

hey @ACuriousMind, I know this hasn't really been discussed at all, but is the part of your meta post discussing, um, inappropriate language/stuff still in affect? (Just curious, you may wish to clarify that.)

0celo7

@heather you'd better not be talking about me

heather

@0celo7 no...? I don't think I've ever heard you use uber-inappropriate language.

*seen

0celo7

uber?

@heather are you saying I have used inappropriate language?

I will remind you that you swore on the bible

no answer!

heather

9:50 PM

@0celo7 occasionally, yeah, you've used cuss words and engaged in activity I would not.

that does not mean I think any less of you. You're an adult, and you're allowed to do that. I'm a kid, so I have naturally lowered ideas of what inappropriate is.

0celo7

@heather can I sue a kid for libel?

heather

@0celo7 libel's only when it isn't true, i'm pretty sure.

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