The h Bar

Slereah

11:00 PM

You don't even have a position operator in QFT

0celo7

@Slereah QFT is wrong QED

Slereah

LQG has a discrete distance operator, tho

ACuriousMind

@Slereah There is the Newton-Wigner operator, which is the proper generalization of the position operator, but yeah, it's not really the position operator.

0celo7

@ACuriousMind even loop gravity?

ACuriousMind

@0celo7 That's not a well-accepted quantum theory.

0celo7

11:01 PM

damn fine print

Slereah

But yeah it has a discrete operator

0celo7

is String theory well-accepted?

Richard

Can I make it spin so fast that it tears itself apart?

0celo7

in your curious mind

@Richard @Richard No.

Please see the above image. It is the mathematical proof that there is no way for them to split. At all. No possible way.

user54412

@Richard Whether black holes are elongated is a coordinate-dependent thing. It's not clear how to answer that question objectively.

ACuriousMind

11:02 PM

@0celo7 No, that's not a "well-accepted quantum theory", either. "well-accepted quantum theory" means QFT, period.

Slereah

Standard model, even

0celo7

@ACuriousMind your face is not a well-accepted quantum theory...

John Duffield

@ACuriousMind : the void in the fabric of space and time is the thing. The coordinate speed of light is zero. There is no way to define space or time.

Slereah

Have all the quantum gravities

I keep them around just in case

user54412

@Richard There is an upper bound on spin before classical black holes become naked singularities. As it turns out, though, anything you try to do to reach that limit just doesn't work. If an object has so much angular momentum that consuming it would push a black hole beyond this limit, the object also has too much angular momentum to fall in in the first place.

0celo7

11:04 PM

@ChrisWhite I'm hand waving here...maybe because the other black hole, should it form, cannot escape the horizon of the other and is doomed to hit the singularity again?

Richard

OK. We seem to be getting back into some abuse and name-calling

Slereah

There's a fun bit in Visser that points out that if we treat particles naively with GR

0celo7

@Richard huh?

Slereah

Then neutrinos would be naked singularities

Because their spin is vastly superior to their mass

Richard

@0celo7 - It's like flag-a-palooza 2015 in here

0celo7

11:06 PM

@Richard No idea what that means TBH

NeuroFuzzy

@0celo7 You have been placed on cooldown for $\infty$ days for the following message: "Your face is a quantum field theory". Please use more polite language in the future.

It's very hurtful :^(

0celo7

Did @Richard not see that as a joke perhaps?

ACuriousMind

@JohnDuffield What does "void in the fabric of space and time" even mean? Write down the metric for this thing and we have something to talk about

@0celo7 You did say something else that was flagged.

0celo7

@ACuriousMind ACM the GR warrior

Richard

@0celo7 - Indeed.

0celo7

11:09 PM

@Richard I feel you have a right to know that.

Like I said, you can interpret that any way you wish.

ACuriousMind

@0celo7 Unlike you, I do not denounce theories I don't like as heresy ;)

0celo7

@ACuriousMind All nuclear processes are quantum :(

Slereah

The liquid drop model doesn't use QM

but it's a bit of a rough model

0celo7

@Richard OH flaga-palooza. I was trying to figure out what flaga is.

ACuriousMind

@0celo7 where's that image Kyle likes to post...

0celo7

11:12 PM

grr

ACuriousMind

Heh, just searching "Picard" in this room gives plenty of images to choose from.

John Duffield

@ACuriousMind : there is no metric. Light doesn't move. You can't measure anything. There's no coordinate system either. See the "frozen star" interpretation in Kevin Brown's Formation and Growth of Black Holes.

0celo7

There is no metric?

Slereah

there is only Zuul

0celo7

But Einstein came up with the whole metric thing, didn't he?

ACuriousMind

11:13 PM

The metric is a lie, apparently.

Slereah

Hm

Another entire page without a single equation

0celo7

@JohnDuffield Can you please cite Einstein for your "there is no metric" comment?

Because I have his book...there's plenty of metrics in it.

Feeds

Richard has frozen this room.

Richard

Please stop being rude to each other. It's a substantial breach of the sites "Be Nice" policy.

This room was placed in timeout for 1 second; the topic of this room is "General chat for Physics Stack Exchange (physics.stackexchange.com). For MathJax use meta.math.stackexchange.com/a/3297#3297"; - conversation should be limited to that topic.

Stack Exchange

Loong has unfrozen this room.

obe

11:17 PM

huh?

Richard

Oh, that worked

0celo7

We're bad people apparently.

John Duffield

@ACuriousMind : the metric is not something that's out there. It isn't space. It's an abstract thing, derived from your measurements of time and space, typically made using the motion of light. When light doesn't move, you can't measure time or space, and you have no metric.

Richard

@Loong - Cheers

0celo7

On another note

Thanks UTK

Loong

11:18 PM

@Richard ;-)

Slereah

"You've earned the "Outspoken" badge (Post 10 messages in chat starred by 10 different users)."

Oh boy

Gee golly jeepers

ACuriousMind

@JohnDuffield No, the metric describes the geometry of spacetime. The entire content of General Relativity is that the presence of matter and energy (in the form of the stress-energy tensor) determines the metric, and that the metric determines motion by geodesics. That's exactly what the Einstein equations tell us.

Slereah

I suspect that Duffield's problem stems from Schwarzschild coordinates

Maybe someone should tell him about Eddington coordinates

or Kruskal or whatever

Richard

@0celo7 - No, you're not. If people can't be civil, they can at least be silent

ACuriousMind

@Slereah I guess you've made enough silly jokes ;)

11:22 PM

@Slereah lol, blocked.

Slereah

It is circus music

I guess you are in a land where circus music intellectual property is important

ACuriousMind

Yes, it would seem that way.

Slereah

That music is from 1897, a bit late for blocking!

Although I suppose that the recording of that one is more recent

ACuriousMind

Well, the blocking message says that it "could" contain music that is protected. So they're not sure, apparently.

John Duffield

11:27 PM

@ACuriousMind : spacetime is an abstract thing too. Light moves through space, not through spacetime. The entire content of GR is not what you've been taught. Remember the gravastar. Now think of your metric as something coloured blue. Now look at this picture. And this one.

ACuriousMind

@JohnDuffield Physics does not deal in pictures. Neither does it deal in words. It deals in quantitative predictions and descriptions. And such description proceeds through abstraction. These pictures tell me nothing.

Slereah

Just ignore him.

John Duffield

@Slereah : re Eddington-Finkelstein coordinates, read the opening paragraph of the Wikipedia article: They are named for Arthur Stanley Eddington[1] and David Finkelstein,[2] even though neither ever wrote down these coordinates or the metric in these coordinates. Roger Penrose[3] seems to have been the first to write down the null form... Most influentially, Misner, Thorne and Wheeler, in their book Gravitation, refer to the null coordinates by that name.

ACuriousMind

...does anyone else see @Loong 's picture blink randomly? It irritates me.

We can't have .gifs as pictures...can we?

Slereah

it does, yes

Loong

11:35 PM

@ACuriousMind ?

Slereah

i.stack.imgur.com/qOgfm.png?s=328&g=1

Seems to be a regular picture

John Duffield

@ACuriousMind : This tells you everything you need to know. Provided you also know that light can't go slower than stopped.

Richard

@ACuriousMind - I think you might be having a seizure

ACuriousMind

@Loong It...just becomes a bit brighter for a moment, then fades again

Slereah

I think that's just that when a user is inactive, his avatar goes in muted color

Which is very visible with Loong

ACuriousMind

11:37 PM

No, it occurs twice or more even when they've done nothing to become active again

Noone else's picture does this

Slereah

Yeah I see it too

gonenc

what is now the new convention for the terminology regarding mass/energy?

Slereah

What do you mean

ACuriousMind

@Slereah Okay, so you and me are both having the same seizure.

gonenc

old use was rest mass $m_0$ and the mass = $\gamma m_0$

but I know that this convention has changed

Slereah

11:40 PM

The mass in modern terms is the Casimir invariant generated by translation invariance

ACuriousMind

Oh, that...I'd say you call "the mass" the invariant mass $m^2$ in $p^2 = -m^2$, at least that's how it is in QFT

Sleerah said it slightly more abstract :)

Slereah

That's why you can get like

Massless fields acquiring a mass

gonenc

@ACuriousMind then what is the variant mass called?

Slereah

It is not called.

gonenc

the old $ \gamma m_0$

Slereah

11:41 PM

Relativistic mass isn't really used anymore

ACuriousMind

@gonenc Sometimes "relativistic mass", but you shouldn't really use that anymore

It's not a Lorentz invariant, and everything can be phrased in terms of invariants, and should be.

Slereah

Relativistic mass is useful as a concept for bridging classical and relativistic mechanics

But within relativistic mechanics proper, it's not really meaningful

gonenc

@ACuriousMind I see the point now why people don't like it

they should teach the new convention in high schools too

ACuriousMind

@gonenc School physics in relativity and quantum mechanics is laughably outdated, if taught at all.

gonenc

@ACuriousMind I know people use $mv^2/2$ to solve particle in a box problem in QM

ACuriousMind

11:44 PM

But yes, it should be modernized.

gonenc

anyhow gotta sleep see y'all

Slereah

night

John Duffield

It isn't just school physics that's outdated. Invariant mass varies. See this. Drop an electron, and some of its mass-energy is converted into kinetic energy thence dissipated. Hence the mass deficit.

ACuriousMind

night

Not a vampire, apparently. It's only 2am.

gonenc

@ACuriousMind well it is 3am here :D

ACuriousMind

11:50 PM

Oh, Turkey is a different time zone? Didn't realize that, but makes sense.

Slereah

Finland?

ACuriousMind

I have laundry that finishes at 3am :D