The h Bar

@Kaumudi.H That looks fine. You'll note the three icons on the right are enabled in your installation and disabled in mine. That's because I usually don't bother with them as I don't think they are worth the CPU cycles. But there's nothing wrong with them.

DanielSank

@Kaumudi.H tiger balm is magic.

John Rennie

You basically have a fully workign AVG install that hopefully won't thrash your CPUs this time.

user228700

@JohnRennie You want me to change something?

AccidentalFourierTransform

5:24 PM

whats a tiger balm?

John Rennie

@Kaumudi.H I'd be inclined to leave things as they are for a few days and see how you get on. It might have been a bit scary, but (a) your AVG is working fine and (b) WE FIXED THE OVERHEATING!!!! :-)

user228700

:-D YES!!!

Slereah

@Danu Long ray

Balarka Sen

we can fix overheating? i thought people let the thing overheat until it's cooked

or explode, in which case the user dies in the explosion

user228700

Are u sure that it's been installed properly though? I am not :-P

John Rennie

5:26 PM

@BalarkaSen if only ... That would make support calls a lot shorter :-)

Danu

@Slereah Not a manifold

:'(

user228700

@JohnRennie ._.

John Rennie

@Kaumudi.H It looks fine to me. We can check using Team Viewer if you want ...

Slereah

No manifold racism please

All manifolds are beautiful

user228700

@JohnRennie That'd be swell but I feel like I've troubled you enough already ._.

Slereah

5:27 PM

Witness this rainbow of manifold diversity

John Rennie

It's OK. It will only take 5 mins. Run Team Viewer and mail me the Your ID code.

Balarka Sen

@JohnRennie also you get to explode with dignity, unlike this fellow

John Rennie

Ooh Scanners!!

0celouvsky

What does completeness mean for a manifold with boundary?

John Rennie

Exploding heads!!

Balarka Sen

5:30 PM

cool stuff eh

0celouvsky

@JohnRennie is that @ me?

John Rennie

@0celouvsky Eh?

0celouvsky

I guess it would have to be "closed bounded sets are compct"

So geodesic balls are compact

@JohnRennie are my balls making your head explode?

John Rennie

Have you never seen the Cronenberg film Scanners?

Balarka Sen

no you weirdo he's talking about the thing i linked

i don't expect 0celo to see weird shit like this

user228700

5:32 PM

Bernardo Meurer

That's some fast internet right there

user228700

OK, yeah, no, we'd better skip that :-P

John Rennie

Ah, I must have not installed Team Viewer.

Bernardo Meurer

@JohnRennie Doesn't windows have a built-in teamviewer of sorts?

I recall something like that

user228700

This is weird. It fluctuates b/w 59 mins and 29 mins and 19 mins :-/

John Rennie

5:34 PM

@BernardoMeurer Windows Remote Assistance, but I think only MS can use that.

Bernardo Meurer

@JohnRennie Really? I thought for the Pro-line anyone could

John Rennie

I honestly wouldn't worry about it. Your AVG looks fine to me.

user228700

@JohnRennie Wokay, then! :-D THANK YOU SO MUCH AAHHHH!!!

John Rennie

@BernardoMeurer Windows has an RDP server built in, but you need a direct connection i.e. I would need to be able to connect to port 3389 on K's PC.

Team Viewer and MS Remote assitance use a proxied connection i.e. both parties connetc to a server and the server relays the traffic

Bernardo Meurer

@JohnRennie I see, can't she open the port on her router and let you through?

John Rennie

5:36 PM

On her grandma's router, for which grandma probably doesn't know the password.

Bernardo Meurer

It's password

It always is

user228700

x'D

0celouvsky

Router passwords in America are always 16 digit alphanumeric thugs

AccidentalFourierTransform

"पासवर्ड"

0celouvsky

It's crazy

John Rennie

5:37 PM

@Kaumudi.H if you suspect anything is wrong I'll be around tomorrow, but it all looks fine to me.

user228700

Wokay!

0celouvsky

@Kaumudi.H you might want to discontinue incriminating behavior though

Just to be safe.

user228700

And the night doesn't end here. For one thing, it's close to 11 and I haven't had dinner yet. For another, I gotta fix my SIM and I have to now chat with one of their customer care executives ._.

Anonymous

@AccidentalFourierTransform Lol, I wish we could use hindi passwords :D

user228700

@0celouvsky What incriminating behavior are u refering to? :-P

John Rennie

5:39 PM

@Kaumudi.H under no circumstances reveal that you use a +--- signature!!

user228700

I have no idea what that means.

ACuriousMind

Do not admit to reading Calvin and Hobbes

user228700

@ACuriousMind But why?! :-(

0celouvsky

@Kaumudi.H it would mean mental retardation :/

John Rennie

Do not download animated GIFs of cats!

Balarka Sen

5:39 PM

it's a lorentzian manifold joke. deep stuff

ACuriousMind

@Kaumudi.H That was a joke, referring to the starred message of "Calvin and Hobbes is offensive?!" that was recently on the starborad. Nevermind. :P

user228700

._. Nice.

0celouvsky

@JohnRennie I'm reading a ++++ signature paper. I think his time is imaginary...

Bernardo Meurer

A what signature?

Balarka Sen

plus plus plus plus

user228700

5:41 PM

:-) Alright, @JohnR: THANK SO MUCH!!!! :-D

0celouvsky

++++

Balarka Sen

@ACuriousMind I didn't put the ! after the ? though

John Rennie

@Kaumudi.H at least it wasn't a hardware problem. That would have been harder to fix remotely :-)

user228700

:-)

user228700

Yeah, I'm glad that the fan's OK.

AccidentalFourierTransform

5:42 PM

ACuriousMind

@BalarkaSen ::shrugs::

Bernardo Meurer

What's a ++++ signature?

Or -+++?

Balarka Sen

You don't need to know that. All you need to know is Minkowski's cat died in a car crash

John Rennie

@BernardoMeurer The signs in the metric tensor

Emilio Pisanty

@AccidentalFourierTransform $+++ -$

user228700

5:43 PM

And now I have this:

user228700

._.

Bernardo Meurer

@JohnRennie What's the metric tensor?

ACuriousMind

@Kaumudi.H I have no idea what I'm looking at

AccidentalFourierTransform

@EmilioPisanty eww

John Rennie

5:44 PM

@ACuriousMind online chat for phone support

ACuriousMind

@EmilioPisanty How about +-++?

Emilio Pisanty

@AccidentalFourierTransform yeah, I know, it's gross, innit

John Rennie

@BernardoMeurer you know Pythagoras' theorem?

user228700

> "For another, I gotta fix my SIM and I have to now chat with one of their customer care executives ._."

Bernardo Meurer

@JohnRennie Come on, I'm just a little dumb,

AccidentalFourierTransform

5:45 PM

Dec 16 '16 at 17:58, by AccidentalFourierTransform

Also, in imaginary $y$ axis so that $\eta=(-1,+1,-1,+1)$.

John Rennie

@BernardoMeurer So if you go dx in the x direction, dy in the y direction and dz in the z direction the total distance moved is $$ds^2 = dx^2 + dy^2 + dz^2 $$ Make sense so far?

0celouvsky

I don't know why @AccidentalFourierTransform keeps posting -+++ memes. Only a dirty physicist would use +---. He might be proud of that but the rest of us are quietly chuckling.

Bernardo Meurer

@JohnRennie Yes sir

AccidentalFourierTransform

@0celouvsky why did you assume I'm a he?

Secret

Wax moth larvae biodegrade polyethylene plastic bag

user228700

5:47 PM

@DanielSank It is!

John Rennie

@BernardoMeurer well in spacetime you can't help moving in the time direction, so we have to include dt in the distance moved. But ... the dt term gets a minus sign: $$ ds^2 = -dt^2 + dx^2 + dy^2 + dz^2 $$

AccidentalFourierTransform

no it doesnt

the $x,y,z$ do

Balarka Sen

go away man

0celouvsky

@AccidentalFourierTransform I don't really care

Balarka Sen

time is the imaginary component

0celouvsky

5:48 PM

Good guy balarka

John Rennie

Where $ds^2$ is now the total distance moved in spacetime - the proper distance

0celouvsky

@JohnRennie ds^2 isn't a number but I will let it slide for pedagogical purposes.

John Rennie

@Bernardo because the signs are -, +, + and + we call this the -+++ signature.

@0celouvsky tensor product then (I say that as if I understood it :-)

Balarka Sen

a tensor, yeah

0celouvsky

In Einsteins derivation of SR he had that with small distances, it really was an equation of numbers

But in GR it doesn't make sense

John Rennie

5:50 PM

@Bernardo in fact that one equation, called the Minkowski metric, is all you need to understand special relativity. All the time dilation, length contraction, blah, blah, stems from that one equation.

Bernardo Meurer

@JohnRennie Ah, and some people do +---?

John Rennie

Both forms are equally good, but people are prone to taking sides ;-)

0celouvsky

@JohnRennie ...you need to have equations of motion too

Bernardo Meurer

@JohnRennie That's really nice

John Rennie

Blood has been shed over which is the RIGHT form :-)

0celouvsky

5:51 PM

@JohnRennie no, +--- is wrong.

Balarka Sen

@BernardoMeurer only the weirdos do

0celouvsky

Spacelike hypersurfaces are not Riemannian. It's nonsense.

John Rennie

@0celouvsky I agree. -+++ is th obvious extension of the 3D Euclidean metric.

Balarka Sen

it's like talking about riemannian metrics but which are negative definite

Slereah

aka not riemannian metrics

Balarka Sen

5:52 PM

aka silly

0celouvsky

Particle physicists use +--- because it removes some minus signs in their equations. I take it as a sign that the whole field is corrupt and deeply flawed.

3

Balarka Sen

lol

user228700

Wokay. Bye, everyone! :-) (@JohnR: THANK YOU AGAIN!!!)

AccidentalFourierTransform

I AINT NO PARTICLE PHYSICIST

John Rennie

@Kaumudi.H Goodnight. I'm off too, to read my book and maybe drink a glass or two of beer.

Bernardo Meurer

5:55 PM

@JohnRennie Why can't it be ++++? Why must time get a -?

user228700

Have a nice evening :-)

John Rennie

Now I've taught @Bernardo all there is to know about SR :-)

0celouvsky

@BernardoMeurer Roughly, a clever application of the Pythagorean theorem.

Bernardo Meurer

Why do we need two relativities?

John Rennie

@BernardoMeurer experiment tells us the sign of dt is different to the other three terms. That's just the way it is. There's no mathematical reason why the signature should be that way.

Bernardo Meurer

5:57 PM

@JohnRennie How the hell does an experiment tell you that?

0celouvsky

Speed of light is the same in any intestinal frame.

AccidentalFourierTransform

by measuring the gravitational field, duh

Balarka Sen

@0celouvsky intestinal frame sounds very interesting

a new cronenberg movie

Slereah

If it was $(++++)$ it would just be euclidian space

0celouvsky

I meant inertial, clearly.

Slereah

5:58 PM

you could just walk backward in time

John Rennie

@BernardoMeurer There really isn't any difference between SR and GR. For GR the metric has basically the same form but (in the simplest cases) changes to $$ ds^2 = -g_{00}dt^2 + g_{11}dx^2 + g_{22}dy^2 + g_{33}dz^2 $$ where the $g$s are components of the metric tensor.

Balarka Sen

I like that explanation @Slereah

0celouvsky

Mostly false @JohnRennie

John Rennie

SR is just the special case where the $g$s are -1 or +1

Slereah

@JohnRennie you forgot the diagonal terms!

Balarka Sen

6:00 PM

@0celouvsky He's just writing it in a coordinate-nonfree way

0celouvsky

I mean the statement that they're basically the same

John Rennie

@Slereah off diagonal terms?

Slereah

yes

0celouvsky

They're not. Not even qualitatively.

Balarka Sen

huh

Slereah

6:01 PM

yeah, the topology of space may also differ in GR :p

John Rennie

@Slereah that's why I said in the simplest cases.

Balarka Sen

I thought it was -+++ metric on a 4-manifold

0celouvsky

It is

But that's the only similarity

John Rennie

@Slereah let's not scare the beginners with too much too soon.

0celouvsky

And GR is SR in "small regions" in "free falll"

John Rennie

6:02 PM

@0celouvsky The Minkowski metric is a vacuum solution of Einstein's equation. Yes?

Slereah

Or for far removed regions outside of gravitational fields

Like intergalactic space or Cleveland

Balarka Sen

interesting

0celouvsky

@JohnRennie yes, but the existence of the Poincare group means the theories are treated completely differently

Slereah

(although you can still have gravitational waves)

0celouvsky

And zero curvature, uninteresting topology, constant metric

John Rennie

6:03 PM

@0celouvsky it's convenient to do that, but you don't have to.

Anyway, my beer is getting warm.

Having stunned the room with the depth of my insight I'm going to leg it sharpish like before they recover.

0celouvsky

@Slereah one of the math profs has Polchinski, Wald, Peskin, Glimm Jaffa

I should get to know him

I can see them through his door

Slereah

Am I him

It's not impossible

0celouvsky

@Slereah apparently "probabilistically complete" manifolds are a thing

Slereah

It is a thing, but what thing would that be

Is it when the manifold is probably complete

can't know for sure

0celouvsky

It's when $v(M)<\infty$

so by renormalizing you get a probability space

Slereah

6:13 PM

neat

0celouvsky

dunno what good it does, but it's in this Schoen and Li paper

Slereah

although, doesn't the manifold already have a measure on it

Such that $\mu(M) = 1$

The measure used to define the time function

0celouvsky

they mean $v(M)=\int \sqrt g\,dx$

Slereah

I assumed, yes

it is the action for 2D quantum gravity, btw

just a big old volume

John Doe

Hello all

Slereah

6:16 PM

Hello one

0celouvsky

slammin

@Slereah I'm guessing complete for a $\partial$-manifold means your geodesic exists until in runs into $\partial M$

Seems reasonable.

Slereah

well a manifold with boundaries can still have just regular old singularities

it could just go into a singularity that's not a boundary

0celouvsky

and we're ruling that out

the only singularities are boundaries

John Doe

Is it correct to state that the expectation value as a function of time is equivalent in both the Schrodinger and Heisenberg picture and hence $\frac{d\langle A\rangle}{dt} = \frac{1}{i \hbar}\langle[A, H]\rangle$ holds in both, where the equation comes from the Heisenberg equation of motion i.e. $\frac{dA^{(H)}}{dt} = \frac{1}{i \hbar}[A^{(H)}, H]$. ?

ACuriousMind

@JohnDoe Yes.

0celouvsky

6:25 PM

Hmm. The proof doesn't use completeness anywhere and the original paper doesn't mention completeness.

ACuriousMind

That's Ehrenfest's theorem and indeed its derivation in the Heisenberg picture is as trivial as you say

0celouvsky

I'm trying very hard @ACuriousMind

John Doe

@ACuriousMind Okay great thanks.

0celouvsky

I won't ask what that derivative means

You should be proud

@Slereah is $\sqrt R\coth(r\sqrt R)\le r^{-1}+\sqrt R$?

I don't even know what coth looks like

ah

Slereah

I don't think anyone does

0celouvsky

6:27 PM

yeah that seems reasonable

Slereah

It's one of those seldomly used function

0celouvsky

@Slereah you can estimate the Laplacian of the distance function (on a Riemannian manifold, in a distributional sense) using cot and coth

Slereah

that sounds unpleasant

0celouvsky

It is, and the proof is bad

I had to prove Green's theorem for Lipschitz functions

I am getting better at these things, so it's not that bad anymore

He's up to 10 constants

this is just silly

Slereah

not even bothering to give them a name

0celouvsky

6:38 PM

Now there's $C_{12}$

I don't see $C_{11}$...

Slereah

maybe he deleted that part and didn't bother changing the numbering

Bernardo Meurer

@DanielSank Yo

0celouvsky

$C_{11}$ doesn't show up until chapter 13 according to the search function

Slereah

Reading about quantum interpretations is not fun

I have to read up on Kolmogorov probability theory :(

0celouvsky

Do you know measure theory

Slereah

6:42 PM

Hey, that book actually mentions a representation of Hilbert spaces that isn't $L^2$

Not very

Bernardo Meurer

A plane describes a spiral trajectory, in a windless day, having, in a certain cartesian referential, the following coordinates in the horizontal plane: $x(t) = (r_0 - kt)\cos(\omega t);y(t) = (r_0 - kt)\sin(\omega t)$ with $r_0 = 600m$, $k=5.0 ms^{-1}$, $\omega = 0.08 rad\cdot s^{-1}$, with $t$ in seconds.

Slereah

$\mathfrak l^2$, the space of sequences of complex numbers with converging absolute squares

0celouvsky

That's an L^2.

Bernardo Meurer

Find the expression for the absolute value of the speed of the plane in function of $t$

Slereah

Well yes, obviously

0celouvsky

6:43 PM

It's L^2 on N with counting measure.

Slereah

Since Hilbert spaces are all the same

0celouvsky

It's isomorphic to the usual one

@Slereah no.

All separable ones

Slereah

Plz

Who cares about non-separable Hilbert spaces

0celouvsky

There are L^2s that are not separable.

Slereah

It's like non-paracompact manifolds

they are too big

And just like people who are too big, they are scorned by society

0celouvsky

6:44 PM

...

DanielSank

@BernardoMeurer Ok, so what did you do?

Bernardo Meurer

@DanielSank Let's make a room

DanielSank

go for it

Slereah

the scan job on this book is really bad

Anonymous

@BernardoMeurer Just differentiate the trajectory to get velocity...

Slereah

6:48 PM

Look at that random mish mash of OCR and scanned letters

Sir Cumference

Wait, can mods see real names on SE?

Slereah

"$A$ is self-adjoint if $A = A^\dagger$"

lol

ACuriousMind

@SirCumference Yes, but access to that is logged - as is access to all PII - and we usually don't look there without good reason.

AccidentalFourierTransform

if $A=A^+$

Slereah

I think I'll have to actually buy that book

the scans are horrendous

damn, it's expensive

"In fact, all major schools in the philosophy of probability, the subjectivists, the a priori objectivists, the empiricists or frequency theorists, the proponents of the inductive logic interpretation and those of the propensity interpretation, laid their claim on this notion."

It's like probability school just finished and they're all going to camp

I fear to imagine what a full list of quantum interpretation would look like

There's a spooky amount of bickering over every detail

Sir Cumference

7:22 PM

@ACuriousMind "Logged"?

Mostafa

@SirCumference Other mods can see.

Like Wikipedia's checkuser

Sir Cumference

Gotcha

DanielSank

@ACuriousMind ~sigh~ I would need to become a licensed wine shipper to send you mead.

I'll look around for some more permissive service. Within my country, this sort of thing only requires license if you ship over a certain amount. It looks like international rules are more strict.

ACuriousMind

I wonder if @JohnRennie is a licenced laptop shipper

Mostafa

A curious cat

36 3

stackexchange.com/users/10437810/shit-acurious-mind

Slereah

7:37 PM

apparently in the biz of physics, there's at least three things called an "interpretation"

Quite a nightmare

ACuriousMind

@Slereah Don't study literature, then :P

Mostafa

@ACuriousMind These guys look dangerous, especially in this performance

Slereah

"Having thus far encountered three different meanings of "interpretations", the interpretation of $F$ by $R$, the interpretation of $F_R$ by additional principles, and the construction of $M$, we are now led to a fourth meaning of the term"

Noooo

ACuriousMind

@Mostafa Do I want to know why you are crawling through the chat transcript? :D Anyway, "dangerous" would have been the last thing I'd associate with Knorkator

Mostafa

7:56 PM

@ACuriousMind Are you just a curious mind, or a-curious mind?

0celouvsky

@BenNiehoff so it turns out there is a rigorous theory of ODE asymptotics like we were discussing

Mostafa

urbandictionary.com/define.php?term=A-Curious

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