Anonymous at Thu, 10 Oct 2024 09:43:59 UTC No. 16418921

>>16418911
No. I have a copy of Rovelli’s book.
>muh Lorentz invariance
He gives arguments as to why area and volume operators’ eigenvalues shouldn’t be interpreted as shapes in space that get contracted. This is like someone complaining that the electron in a hydrogen atom doesn’t radiate and decay onto the nucleus.
>muh Lorentz covariance
This is even fucking dumber. LQG evolved from the canonical formalism of GR. Hamiltonian mechanics do explicitly separate out time and space, but they are still implicitly covariant. You can always transform to the Lagrangian formalism if you really want to. We have the canonical formalism in the regular old quantum field theory and nobody questions it. It was the historically preferred way to do things because Dirac’s quantiziation recipe is much easier to justify than path integrals both physically and mathematically. Mathematicians will still tell you path integrals are nonsense btw.

Anonymous at Thu, 10 Oct 2024 09:54:00 UTC No. 16418934

>>16418911
>physics is dying because no one will listen to me other than my simps, wah wah
actual woman moment

Anonymous at Thu, 10 Oct 2024 10:18:39 UTC No. 16418950

>>16418921
>He gives arguments as to why area and volume operators’ eigenvalues shouldn’t be interpreted as shapes in space that get contracted.
And what are the actual arguments?
>Mathematicians will still tell you path integrals are nonsense btw.
Because they are.

Anonymous at Thu, 10 Oct 2024 10:19:40 UTC No. 16418951

>>16418934
This is more Jews vs. actual good researchers tired of seeing tax money wasted.

Anonymous at Thu, 10 Oct 2024 10:30:58 UTC No. 16418963

>>16418950
>And what are the actual arguments?
They’re operators arising from canonically quantizing GR. Lengths are measured via the metric, which is the gravitational field. When the metric (gravity) is quantized, the lengths no longer commute and behave like operators with eigenvalues. Notice how none of this involves any geometric construction in space or spacetime.

Rovelli is of the opinion that spacetime is a “gauge redundancy” of sorts and a proper quantum gravity theory should only be concerned with dynamics of the fields themselves. He gives Einstein’s hole argument as an example of this redundancy due to diffeomorphism invariance.

Anonymous at Thu, 10 Oct 2024 10:35:49 UTC No. 16418966

>>16418951
Didn't know Sabine was a Jew, would explain a few things.

Anonymous at Thu, 10 Oct 2024 10:46:59 UTC No. 16418979

>>16418963
Let me elaborate on this a bit more. Length is given by [math]L = \sqrt{g_{ab}x^ax^b}[/math] in classical GR. Here [math]a,b[/math] are spatial indices, not spacetime ones. L is already classically not Lorentz invariant. So when the metric is quantized and L becomes an operator, it remains non-invariant. You can still meaningfully talk about it as an operator with eigenvalues. Nothing has changed.

Anonymous at Thu, 10 Oct 2024 11:14:25 UTC No. 16419004

>>16418963
>They’re operators arising from canonically quantizing GR.
Ok.
> Lengths are measured via the metric, which is the gravitational field.
Sure.
>When the metric (gravity) is quantized, the lengths no longer commute and behave like operators with eigenvalues.
You lost me completely, if the lengths don't commute, what meaning could the eigenvalues possibly have?
>Notice how none of this involves any geometric construction in space or spacetime.
I'm not a physicist and not familiar with this transform, but you just stated -and the definitions of the terms you are using imply- that you are working in _space_ equipped with _some_ metric. And in that case a geometric construction should always be possible.

I'm sorry, but I really don't get the point. Did he even prove that the lengths no longer commute? Because even in most discrete spaces (which I assume the quantized metric is) they do.


I would look this up myself, but I can't find his textbook in my library portal.

Anonymous at Thu, 10 Oct 2024 11:20:32 UTC No. 16419008

>>16418966
She is German and gassing the Jews.

Memes aside I don't like her and I think this video "rant" is very unprofessional, but she's far from alone in sentiments about funding body capture for research with no useful fundamental or practical results. It's a major problem across the West and not just in Physics.

People who refuse to defend their work to anyone who is not from their own community should not be getting a dime of tax money.

Anonymous at Thu, 10 Oct 2024 11:27:21 UTC No. 16419011

>>16419004
>You lost me completely, if the lengths don't commute, what meaning could the eigenvalues possibly have?
Most diagonalizable matrices don’t commute, yet they have eigenvalues. As for meaning, Hermitian operators’ eigenvalues in quantum mechanics are observables.
>I'm sorry, but I really don't get the point
Let me put it this way. She complains that a certain operator is not Lorentz invariant. I say “so fucking what?”. The Faraday tensor is also not Lorentz invariant, but we still quantize it to produce Lorentz invariant amplitudes. So that whole complaint is null and void.
>Did he even prove that the lengths no longer commute?
It’s not a proof, but an assumption. Historically, people like Dirac have discovered that quantum behavior can be explained by “quantizing” classical variables, ie by making them obey a commutation relation (essentially turning them into Lie algebra operators). His quantization recipe was then successfully applied to classical field theory by making fields into nonabelian operators. That worked. Then people decided to do it with general relativity by applying this procedure to the spacetime metric. This was all the way back in the 50s-60s, which has eventually led to modern day LQG.

Anonymous at Thu, 10 Oct 2024 13:59:23 UTC No. 16419166

>>16419011
Fair.