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Verlinde scores goal for LQG

by marcus
Tags: goal, scores, verlinde
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tom.stoer
#127
Feb8-10, 01:20 AM
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Quote Quote by atyy View Post
Why can't the degrees of freedom be those of a quantized metric field?
???

They are essentially a "quantized metric field".

There are some details like Ashtekars formulation, spin network states, induced Chern-Simons gauge theory on the horizon, ... but essentially the spin network is what remains from GR
atyy
#128
Feb8-10, 01:28 AM
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Quote Quote by tom.stoer View Post
???

They are essentially a "quantized metric field".

There are some details like Ashtekars formulation, spin network states, induced Chern-Simons gauge theory on the horizon, ... but essentially the spin network is what remains from GR
Yes, that's what I thought. I was saying Jacobson's conclusion is wrong, and Verlinde's too - I believe that by "emergent" they meant that it could not be a quantized metric field. If you read the end of Smolin's discussion, he acknowledges that this is what they meant, but that he disagrees with it, and that their work does not rule out that the degrees of freedom could be a quantized metric field, which would be "emergent" in a Smolin sense, but not a Jacobson or Verlinde sense.
tom.stoer
#129
Feb8-10, 01:40 AM
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I have to check Verlindes reasoning. I would say that there must be "something". Perhaps his approach is generic enough not to specify "something", but w/o "something" there would be nothing at all :-)

I would say that Verlindes idea is to get rid of gravity as a fundamental entity b/c it always causes trouble. So perhaps his argument is viable with fundamental degrees of freedom (regradless what they are in detail), especially if the are not related to gravity.

If you look at it from a particle physics perspective there are enough degrees of freedom to carry entropy. If you look at it from Smolins LQG perspecive it's clear that he needs gravity b/c w/o gravity LQG simply fades away:-)
Fra
#130
Feb8-10, 01:41 AM
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Quote Quote by tom.stoer View Post
I don't like reasoning that uses an observer like the Kopenhagen interpretation b/c you run into trouble with with Wigner's friend(s).
...
So you replace the observer by a generic holographic argument. That's nice.
...
Now you can ask "why fundamental degrees of freedom?" As I said you need them simply b/c w/o them you are not able to produce entropy at all.
...
If this is reasoning is true the main question is: why SU(2)?
I stand by my position, and maybe I could expand later. But I certainly do not think the oldest copenhagen view is enough, since there the observer is a given classical realist structure. Wigner's friend is not a problem for what I have in mind. All I ask is that the action of the observer is entering the abstractions. The observer is not an inert information sink that can ask unlimited kinds and amounts of questions, and encode unlimited information.

With objecting to rovelli I'm not suggesting that the original classical realist observer is the way, I am thinking of a different way but which is closer to the measurement ideal that is the idea of doing away with the observer. To me, it's not possible to do away with the observer.

What one needs to define a measure of missing information, is distinguishable degrees of freedom. But if the distinguishable degrees of freedom are dependent on the observer, the constructed measure is intrinsically relative. I'm not saything there are no degrees of freedom.

About Smolins ideas, he seems to have had more than one. Some of smolins reasoning (I'm thinking CNS and reality of time, evolution of law), are at least in my interpretation in stark contrast to rovelli's RQM ideas.

Questions like why SU(2) are exactly the thinks that I think we could answer if we see it as an evolved equilibrium - rather than as a fixed eternal realist fact. I can't do this, but a possible pathway to doing it is at least visible to me.

I think the symmetries, that more or less are the signatures of the SM might be explainable as self-organising memory structures interact and where the invariants are preferred during different conditions. This means that maybe these symmetries are not fundamental, in the observer indepedent way. I rather think that they are (at best) uniqely expected in the statistical sense for a very constrained class of observers.

/Fredrik
Fra
#131
Feb8-10, 01:46 AM
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About wigners friend, here is my simple reasoning of this.

For simplicity lets consider wigners friend to be somehow soldered onto the mesurement device, so that wigners friend and the apparatous are "one" :)

Then we have two observers.

Wigner and his friend/apparatous.

The fact that wigner doesn't know what has happened (until he speaks to his friend) means his ACTION reflects this. This means we predict an interaction between wigner and his friend. Ultimately this interaction is canceled when they reach an agreement.

This is an analogt but I mean this in a deeper sense, not just that wigner and his friend enter an intermittent argument, but that in a general example wigner and his friend could simply be system A and system B, both interacting with system C.

The idea here, predicts that there is an interaction even between observers!

/Fredrik
czes
#132
Feb8-10, 03:07 AM
P: 216
In 1968 Sakharov wrote the the gravity isn't a fundamental force and it is a secondary effect.
Marcus sent me a good link of 2010:
http://arxiv.org/PS_cache/arxiv/pdf/...911.5004v2.pdf
It is a long paper but it is good to read a summary.

It seems for me that there isn't volume nor surface either. It is just a product of the information and a product seem to show an area.
I prefer probability ρ(x) = |ψ(x, t)|*|ψ(y, t)| instead of ρ(x) = ψ [tex](x, t)^ 2[/tex]
as in Copenhagen Interpretation.
This product of the wave functions shows interesting properties:
Tp / T(x) * Tp / T(y) = -a Fg / Fe
(lp / l x ) * (lp / l y ) = -a Fg / Fe
where Tp is a Planck time, lp is Planck length, lx, ly are Compton wave lengths , a (alfa) is fine structure const. Fg -gravitational interaction, Fe -electromagnetic interaction.

In a computer the information creates a program of the image just in an interaction not in a define space.
tom.stoer
#133
Feb8-10, 03:11 AM
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Let's use an even simpler approach - "shut up and calculate".

We agree that every observer making measurements does not "see" the subsystem itself but only the 2-dim. screen of the subsystem. I don't care how the observer itself is represented as he is located outside the subsystem :-)
Fra
#134
Feb8-10, 03:25 AM
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Quote Quote by tom.stoer View Post
We agree that every observer making measurements does not "see" the subsystem itself but only the 2-dim. screen of the subsystem. I don't care how the observer itself is represented as he is located outside the subsystem :-)
Would it be unreasonable to assume that the representation of the observer, would impose constraints on possible inferred theories about the subsystem itself? - and hence constrains on it's possible actions?

Although the 2-dim screen defines the distinguishable events, further structure can emerge on the observer side of the screen as histories of events accumulate and organise.

Maybe one can find an argument where certain representations are simply more likely to be preserved, and that these represtations have certain symmetries. This is the kind of first principle explanation of the symmetries I seek.

So the inconsistencies of the observer bias, that cricits points out, are turned around and used as interactions that work as a selective pressure to evolve the observer. Then consider that even a particles can be thought of as an observers, one could understand the appearance of preferred particle hierarchies in this sense as expected "optimal representations" rather than "fundamental representations".

/Fredrik
czes
#135
Feb8-10, 03:46 AM
P: 216
Quote Quote by tom.stoer View Post
Let's use an even simpler approach - "shut up and calculate".

We agree that every observer making measurements does not "see" the subsystem itself but only the 2-dim. screen of the subsystem. I don't care how the observer itself is represented as he is located outside the subsystem :-)
And each measurement located on the screen blocks the entropy of the subsystem. Isn't it ?
czes
#136
Feb8-10, 10:43 AM
P: 216
A system is in an equilibrium if it absorbs and emits the same energy.
For example:
A planet surface is a sphere and if we go deeper the subspheres are smaller proportionally to a squared distance from the surface. Therefore the entropy dS=Q/T might be balanced if the temperature T increases proportional to the squared distance from the surface according to dS=kA/4 [tex]L^2[/tex]
A=area of the subsystem
L= Planck length

It seems strange how the systems with different temperature may be in thermal balance but it is in our Earth and we use it by pumping cold water into thermal deep hole and taking a warm water.
Hans de Vries
#137
Feb18-10, 02:18 PM
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Quote Quote by Hans de Vries View Post
Question: Why do things fall down according to General Relativity?

Answer: Elementary Wave behavior!

Gravitational time dilation causes the higher part of the wavepacket to oscillate
faster as the lower part and as a result the vertical spatial frequency increases,
corresponding to a continuous increasing momentum and (according to Fourier)
a downward accelerating wave packet.

Regards, Hans


A sort of coincidence but this role of the wave behavior in gravitational acceleration is
now proved with a 10,000 fold improvement: better as one part in 100 million (7x10-9)

Atom Interferometer Provides Most Precise Test Yet of Einstein's Gravitational Redshift

http://www.sciencedaily.com/releases...0217131125.htm



It's pure Mathematics: A wave packet in a potential field (which causes different
frequencies at different places) will accelerate in the direction were the frequency
is lower. This is just the same as the acceleration of a charged wave packet in
an electric potential field (see my book Section 11.6 and shown in figure 11.4)

EM Lorentz force derived from Klein Gordon's equation

http://www.physics-quest.org/Book_Lo...ein_Gordon.pdf


Regards, Hans


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