How Does Verlinde's Theory Link LQG with Newtonian Gravity?

[MTd2]

It may be me but I can't find anything in the idea of "entropic force" which fits into a wave behavior picture...

There is no equivalence principle issue here because in the paper by Verlinde, is about Newtonian gravity. So equivalence principle IS violated. But the quantum corrections due entropy that makes Newtonian gravity in the problem arise are of much larger magnitude or relevance than GR or interference patterns of neutrons.

And even so, I don't really see any issue here. In this set up, gravity is not a force, there is no particle to create gravity, if this were a paper on GR, you could say that geometry is bent by entropy. So, there is not an interference from gravity, because there is simply no gravity. It is exactly like if you used mirrors inside experiments to study coherence. The path is changed, but not the other states of the particle.

Let me put in other way. Entropy, here, is more like a new kind of mass.

 

[czes]

The Zitterbewegung is a rather outdated concept, that is, there is nothing physically
vibrating and certainly not at c. To understand this better one can linearize the Klein Gordon equation, which is possible
in 1+1d, into a Left and Right moving component which are both moving at c but are
coupled via the mass term allowing propagation speeds lower than c.
I did this here: (in sections 16.1 through 16.4)
http://physics-quest.org/Book_Chapter_Dirac.pdf

There are computer simulations shown in figures 16.4 and 16.5. which obtain the
propagation of a Klein Gordon particle's wave-packet in this way.
Regards, Hans

Thank you Hans for the link of your book. I have printed it for me.
I agree there isn't a motion on a quantum fundamental level but there is a wave function which is an information any way. We do not observe a wave function alone as we do not observe an information alone either. We observe an interaction between wave functions. It is shown as a probable information of the particle due a squared wave function in Copenhagen. In other interpretations wave function is more real. This information shows a Compton wave length L=h/mc shown in Klein -Gordon equation.

A. We observe the indirect effects of the wave function as the existence of the particle so it has interact with an environment.
B. If the Compton wave length is a quantum information it has to be non-local due to Bell's theory

If the wave functions interact with each other and are non-local it has to represent something.
I assume it is distributed inversely proportional to the distance from a source of the oscillation represent a background information space.

 

[marcus]

Nice! I'll take a look at your book.Christine

Impressive work in progress, Hans!
Online introduction to relativistic quantum field theory with lots of illustrations, aids to intuition.
It looks like your plan is to cover the subject in 30 chapters, and you already have 14 chapters (all or part) filled in.
In case anyone didn't check it out already, the main chapter menu is here:
http://physics-quest.org/
This has links to the 14-or-so chapters which are all or part completed.

 

[marcus]

Ted Jacobson's 1995 paper is in some sense seminal here---at the root of all this discussion.
I thought it would be good for people to have a glimpse of the actual person:
http://math.ucr.edu/home/baez/marseille/jacobson_rovelli.jpg

This is Jacobson at the first Loops conference, Loops 2004, having a quiet conversation with Carlo Rovelli.

 

[czes]

Ted Jacobson wrote yesterday an article:
Extended Horava gravity and Einstein-aether theory
http://arxiv.org/abs/1001.4823

I think, we may use here a non-local information of the particles oscillation as a physical example of a matter field in Jacobsons theory.

 

[MTd2]

Hi Marcus, check your PMs! :)

 

[Fra]

I share some of these objections/comments...

Fwiw, I'll interject some of my personal views on this.

But I don't really know what "sides" means in a world without geometry.

Good point. One certainly wonders what "distance" means.

In my a the screen can be loosely defined informationally by means of what's predictable and what's not. I envision it like this. Prediction relate to a an observing system, making a prediction. This observer has a complexity. At some point, the predictability of constructed events are so small that it can not be distinguished from zero by a code of limited complexity - here is a natural "relative" horizon of measureable events.

This relates to the problem of how to conceptually handle the meaning of events with zero probability happen? - as I see it, yes then can, but that's irrelevant from the point of view of the ACTION of the observing system, the _expected_ action is invariant with respect to zero probability events, this is am abstract form of "locality". Instead this is where undecidability comes in. Part of the action is always undecidably as I see it - this is where the evolutionary parts comes in. This certainly limits the possibility of making certain predictions of anything. But I still think acknowledging this may improve our undertanding.

He also seems to assume that one side has "already emerged", but how did this happen? Smolin assumes the same thing in his paper, which is quite strange in my opinion.

I can't accept that either. But, I like to "read it" as a temporary working premise in order to show the implications.

I've encounted this exact problem in my own thinking, and the best resolution out of it I have found is to complement this "statistical information view" with an evolutionary view in darwinian style.

So this is why I think we need to start a the smallest complexity scale - which should be unique, and then ponder how higher order organization emerges as complexity increases.

I think his starting points, must in a satisfactoty future treatment be a result of such a process. It's that process I I also need to understand. I think there is a more information theoretical possibility to this than smolins CNS. Something that is formulated in terms of more abstraction "information channels" or screens, rather than explicit black holes.

/Fredrik

 

[Physics Monkey]

I can't accept that either. But, I like to "read it" as a temporary working premise in order to show the implications.

I certainly agree with you here. I have no logical problem with taking some of the space as emergent and trying to show that more "emerges". I'm not sure how natural a starting point this is, but regardless of my opinion, it indicates that Verlinde and Smolin both use background notions to make progress.

One place where your discussion of minimal complexity, etc strikes me as especially relevant is the case of our own universe (roughly de Sitter). A de Sitter spacetime contains a horizon that apparently limits the size of the physical HIlbert space available to observers in the space. Similarly, observers in de Sitter have limitations on how precisely they can measure various physical quantities. A classic reference is the article of Witten http://arxiv.org/abs/hep-th/0106109

 

[atyy]

Similarly, observers in de Sitter have limitations on how precisely they can measure various physical quantities. A classic reference is the article of Witten http://arxiv.org/abs/hep-th/0106109

"For life itself is only an approximation, valid in the limit of a complex organism or civilization." He means this to be true in any physics, not just in asymptotically ds Sitter spacetimes, right?

 

[Physics Monkey]

"For life itself is only an approximation, valid in the limit of a complex organism or civilization." He means this to be true in any physics, not just in asymptotically ds Sitter spacetimes, right?

Haha, yes, I would assume so. It's a pretty vague comment though, so who knows what he really means.

 

[marcus]

http://pirsa.org/06090001/

Ted Jacobson gave a 1-hour video lecture on his 1995 paper deriving the Einstein equation from thermodynamics (essentially the Clausius relation) and
including some more recent results, as of 2006.
He gives some conjectures about possible meanings.
I hadn't watched this talk before, for some reason didn't know it existed.

 

[Hans de Vries]

Nice! I'll take a look at your book.


Christine

Hi, Christine (Obrigado!)

Impressive work in progress, Hans!
Online introduction to relativistic quantum field theory with lots of illustrations, aids to intuition.
It looks like your plan is to cover the subject in 30 chapters, and you already have 14 chapters (all or part) filled in.
In case anyone didn't check it out already, the main chapter menu is here:
http://physics-quest.org/
This has links to the 14-or-so chapters which are all or part completed.

Thank you Marcus.

It's more work as I expected I'm currently at 700 pages including the
unfinished chapters and suspect to end up with something like 1100..

 

[Hans de Vries]

There is no equivalence principle issue here because in the paper by Verlinde, is about Newtonian gravity. So equivalence principle IS violated. But the quantum corrections due entropy that makes Newtonian gravity in the problem arise are of much larger magnitude or relevance than GR or interference patterns of neutrons.

And even so, I don't really see any issue here. In this set up, gravity is not a force, there is no particle to create gravity, if this were a paper on GR, you could say that geometry is bent by entropy. So, there is not an interference from gravity, because there is simply no gravity. It is exactly like if you used mirrors inside experiments to study coherence. The path is changed, but not the other states of the particle.

Let me put in other way. Entropy, here, is more like a new kind of mass.

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

 

[MTd2]

That doesn't look like general relativity, but some sort of argument to put quantum mechanics, with resort to wave mechanics, in the context. In general relativity gravity is caused because locally the shortest path between two points is parametrized by, and equated to, the momentum energy tensor. In the entropic case, by Jacobson, that is not equated with the energy tensor, but to where entropy is minimized.

Perhaps, here, you could apply your reasoning given that the highest part would be "hotter" than the lower and thus pushing the object.

 

[MTd2]

I still don't see why any interference pattern would be destroyed of the neutron experiment would be destroyed, given that no state relevant to the particles, in the experiment, was changed. Geometry follows the difference of perceived entropy in the environment, not the entropy in the object, in this case, the particles.

 

[Hans de Vries]

That doesn't look like general relativity, but some sort of argument to put quantum mechanics, with resort to wave mechanics, in the context. In general relativity gravity is caused because locally the shortest path between two points is parametrized by, and equated to, the momentum energy tensor. In the entropic case, by Jacobson, that is not equated with the energy tensor, but to where entropy is minimized.

Perhaps, here, you could apply your reasoning given that the highest part would be "hotter" than the lower and thus pushing the object.

It is General Relativity nevertheless.

(notwithstanding all the hand waving rubber sheet and "squeezing/sucking" divergent
coordinate lines metafores used to 'explain' why objects fall)

The behavior of matter is entirely determined by the Propagators/Green's functions and
the resulting wave behavior. Concepts like mass, energy and momentum (and thus the
momentum - energy tensor) become linked to space-time via wavelength and frequency.

Regards, Hans

 

[Hans de Vries]

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

This is closely identical to the acceleration resulting from the EM Lorentz force due
to a potential energy gradient. See for instance figure 11.4 which handles this
component of the Lorentz force derived from the Interacting Klein Gordon equation.

http://www.physics-quest.org/Book_Lorentz_force_from_Klein_Gordon.pdf

Figures 11.3 11.5 and 11.6 handle the other 3 components of the EM Lorentz force.Regards, Hans

 

[MTd2]

If you are talking about wave packets, you are attributing point matter a non local aspect . Maybe you can think like this in a small neighborhood of the particle, where space is flat, and you can approximate about the usual QFT or classical fields with potential. But, strictly talking about this about GR, you are already making extensions to concepts beyond it.

Anyway, that wouldn't change the experiment with the neutron interference.

 

[Hans de Vries]

If you are talking about wave packets, you are attributing point matter a non local aspect . Maybe you can think like this in a small neighborhood of the particle, where space is flat, and you can approximate about the usual QFT or classical fields with potential. But, strictly talking about this about GR, you are already making extensions to concepts beyond it.

Anyway, that wouldn't change the experiment with the neutron interference.

There is no problem extending propagators (in position space) to curved space time.
Massless propagators follow the curved coordinates. Yes it is not generally possible
to do this in an equivalent Fourier transformed coordinate system but one can derive
the wave behavior (in curved position space) in just the same way.

Regards, Hans

 

[MTd2]

Sure, you can, if the curved space is fixed. But if you are considering that such fields significantly change the background, you'd have to consider interactions with gravitons. If this thread was about Asymptotic Safety, I'd have no quarrels about this, and I'd agree with you, but this is about an "entropic force" that serves as the source of "gravity". But "gravity" here is just the shortest path to the lowest value of entropy, there is no graviton here.

 

[marcus]

MTd2 thanks for spotting this 5-page note by Jerzy Kowalski-Glikman
http://arxiv.org/abs/1002.1035
He's a major figure (co-organizer with Chris Meissner of the 2009 Planck Scale conference) and this note is, I believe, more important than its brevity would make you think.
Another chapter in the gravity-as-entropic-force story

A note on gravity, entropy, and BF topological field theory
Jerzy Kowalski-Glikman
5 pages
(Submitted on 4 Feb 2010)
"In this note I argue that the expression for entropic force, used as a starting point in Verlinde's derivation of Newton's law, can be deduced from first principles if one assumes that that the microscopic theory behind his construction is the topological SO(4,1) BF theory coupled to particles."

SO(4,1) is the deSitter group. John Baez contributed a thread on the deSitter group here at PF two or three years back. Connections with a lot of things. At that time I think Kowalski-Glikman was at Perimeter working on DSR. Just saw this, but have to run. I'll get back to it later.

EDIT: Been reading it. It involves a type of *topological defect* (occurring in GR along a curve) discovered by Misner in 1962 and called a "Misner string". This Misner string (not a string-theory string) can be thought of as a singularity, and is analogous to a "Dirac string" a defect which occurs in electromagnetism. The Misner string has associated with it an entropy, proportional to length---as if the entropy were distributed uniformly along the curve. This was unfamiliar to me. Have to look it up. Steve Carlip has a paper about the entropy of the Misner string.

 

[marcus]

You may remember all the Laurent Freidel and Etera Livine work around 2005 on spinfoams in 3D (Ponzano-Regge revisited) where they found that in that simplified situation matter was behaving as topological defects. E.g. like a conical singularity in space that persists thru time.

Apparently the "Dirac string" in electromagnetism is a singularity or defect where a gauge potential cannot be defined. The concept emerged in 1931. A dirac string does not have a definite location---sometimes described as a "fictitious curve". I think all that means is that it represents a topological defect in domain of definition of the potential.

There is a more natural mathematical description in terms of fiber bundles. I just looked at the Wikipedia
==quote http://en.wikipedia.org/wiki/Dirac_string ==
In physics, a Dirac string is a fictitious one-dimensional curve in space, conceived of by the physicist Paul Dirac, stretching between two Dirac magnetic monopoles with opposite magnetic charges, or from one magnetic monopole out to infinity. The gauge potential cannot be defined on the Dirac string, but it is defined everywhere else. The Dirac string acts as the solenoid in the Aharonov-Bohm effect, and the requirement that the position of the Dirac string should not be observable ...
<snippety snip>... can be understood in terms of the cohomology of the fibre bundle representing the gauge fields over the base manifold of space-time...
<snipsnip>... Informally, one might say that the Dirac string carries away the "excess curvature" that would otherwise prevent F from being a closed form, as one has that dF = 0 everywhere except at the location of the monopole.P.A.M. Dirac, "Quantized Singularities in the Electromagnetic Field", Proceedings of the Royal Society, A133 (1931) pp 60–72.
==endquote==

What I gather from several sources is that the Misner string (1962) is the GR analog of the Dirac string. What the Dirac string is to electromagenetism, the Misner string is to gravity.

This all comes (at least to me) as a slight shock. I wasn't expecting to be confronted by the topology of fiber bundles, not this week, at least. However I have been watching Jerzy Kowalski-Glikman since in 2004 and he has a lot of credibility with me. He's steady and doesn't hare about. I'm betting that this topological defect thing will not go away and that this short paper is so-to-speak opening the next chapter of this Jacobson-Verlinde story.

 

[qsa]

What I gather from several sources is that the Misner string (1962) is the GR analog of the Dirac string. What the Dirac string is to electromagenetism, the Misner string is to gravity.

another quote from
Jerzy Kowalski-Glikman
http://arxiv.org/abs/1002.1035


""In fact it turns out that a pointlike source must be
accompanied by a string extending from the source to
infinity.""

here is a quote from my post #28

ok, susskind does use light rays, but he uses light rays to represent a parton(particle) on the screen. Not far enough. I propose a ray from every point in space-time to every other point in space-time. The number of connections(two way) per two points(A,B) will represent the entropy(information) that passes between those two points. the entropy at those points is related to the probability of finding a particle at those points. The entropy at A will affect B and vis=versa in such way to change their probabilities(entropies) to indicate attraction(by lowering the pobabilities at those points, forcing an increase in probabilties in the neighbouring points). This technique works for all forces

In fact Dirac string and misner strings are the same and they represent ENERGY (very important statement). Moreover, all particles are made of them.

arXiv:hep-th/9903229v2 31 Mar 1999

I show that gravitational entropy can be ascribed to spacetimes containing Misner strings (the
gravitational analogues of Dirac strings), even in the absence of any other event horizon (or bolt)
structures. This result follows from an extension of proposals for evaluating the stress-energy of a
gravitational system which are motivated by the AdS/CFT correspondence.


I am glad that people are zeroing in. My Idea will eventually clear up all this mess. Funny, it is going to be in the sprit of Misner,Wheeler Thorne.. Gravitation (and everything ) as pre-calculus.

 

[Berlin]

another quote from
Jerzy Kowalski-Glikman
http://arxiv.org/abs/1002.1035


""In fact it turns out that a pointlike source must be
accompanied by a string extending from the source to
infinity.""

Sounds like C. Schiller to me..
Could it be, yes It could, something's coming, something good.

berlin

 

[tom.stoer]

I did not follow this blog in detail, so perhaps simply I overlooked it: Verlinde wrote a long comment regarding the logic of his paper in Lubos' blog: http://motls.blogspot.com/2010/01/erik-verlinde-comments-about-entropic.html

 

[ensabah6]

I did not follow this blog in detail, so perhaps simply I overlooked it: Verlinde wrote a long comment regarding the logic of his paper in Lubos' blog: http://motls.blogspot.com/2010/01/erik-verlinde-comments-about-entropic.html

If gravity is not a fundamental force, is quantizing it ala LQG the wrong approach to get the fundamental degrees of freedom?

 

[atyy]

If gravity is not a fundamental force, is quantizing it ala LQG the wrong approach to get the fundamental degrees of freedom?

Yes. However, it does not follow that if gravity has a temperature that it is not a fundamental force - I believe Ted Jacobson was in error in his final conclusion of his seminal paper - although that is the view I subscribe to on personal aesthetics.

 

[ensabah6]

Yes. However, it does not follow that if gravity has a temperature that it is not a fundamental force - I believe Ted Jacobson was in error in his final conclusion of his seminal paper - although that is the view I subscribe to on personal aesthetics.

String theory and LQG both model gravity as fundamental force, not emergent.

 

[atyy]

String theory and LQG both model gravity as fundamental force, not emergent.

Gravity is emergent in string theory. See the last slide where "AdS/CFT" is linked to "Emergent gravity" http://dao.mit.edu/~wen/talks/10IPMU.pdf.

 

[ensabah6]

Gravity is emergent in string theory. See the last slide where "AdS/CFT" is linked to "Emergent gravity" http://dao.mit.edu/~wen/talks/10IPMU.pdf.

In followup papers to Verlinde, it's been argued that Verlinde's derivation works only for 3 spatial dimensions, is this correct interpretation?