Gravity is not entropic force ?

[czes]

MTd2 already spotted this one! Looks interesting:
http://arxiv.org/abs/1009.5414
Gravity is not an entropic force - 27 Sep 2010
Archil Kobakhidze claims that if a slit of 15 microns (bilion times the Compton wavelength of neutron) is opaque for a slowly neutrons because of a quantum state formed in the slit, the gravity is not an entropic force.
Could you explain me what the quantum states formed in the potential well between the gravitational field on top and a horizontal mirror on bottom have to do with the origin of the gravity ?
The experiment was performed in 2003
arXiv:hep-ph/0306198

[humanino]

Although I am not always happy with Motl's style, I think his comments on Verlinde's approach have been fair and useful. The paper you point out is essentially the same argument as Motl posted in january
Why gravity can't be entropic (http://motls.blogspot.com/2010/01/erik-verlinde-why-gravity-cant-be.html)

[czes]

Although I am not always happy with Motl's style, I think his comments on Verlinde's approach have been fair and useful. The paper you point out is essentially the same argument as Motl posted in january
Why gravity can't be entropic (http://motls.blogspot.com/2010/01/erik-verlinde-why-gravity-cant-be.html)
Thank you Humanino
Motl's arguments are better understandable for me.
But what this experiment with neutrons has to do with a theory of Verlinde ?

[unusualname]

Thank you Humanino
Motl's arguments are better understandable for me.
But what this experiment with neutrons has to do with a theory of Verlinde ?

Neutron interferometry shows that the quantum wavefunctions are influenced by gravity, in a predictable manner (you can observe phase shifts in the interference as the gravitational field changes)

Any theory of gravity has to explain that, Motl claims Verlinde's approach fails to do so.

[MTd2]

Verlnde`s fails because it is right. He finds newtonian gravity and any deviation of it would be an error, there is no equivalence principle, speed of light as a constant does not make sense, etc.

[Demystifier]

Verlnde`s fails because it is right. He finds newtonian gravity and any deviation of it would be an error, there is no equivalence principle, speed of light as a constant does not make sense, etc.
What are you talking about? In the same paper, Verlinde also develops a general-relativistic variant of entropic gravity.

[czes]

Lubos Motl wrote:
"Holography leads us to imagine that the microstates of any system can be embedded into the quantum bits of a holographic screen that resembles a black hole horizon. However, any viable interpretation must be able to explain that the vacuum is a unique state and there are unique states for any position of the neutron in the gravitational field, and so on. String theory in general and the AdS/CFT correspondence in particular satisfy these constraints while Erik's framework does not."
He is not against the Holographic Principle, I think. He is against the Vacuum-aether made of particles like a ordinary molecules of a gas.

[MTd2]

What are you talking about? In the same paper, Verlinde also develops a general-relativistic variant of entropic gravity.

Yes, thanks. But the argument still does not hold because it supposes that the neutron cannot start with a zero entropy. On the top of page one:

"The above equations (10) and (11) tell us that even if we start with a pure neutron state
rN (z) at some z, i.e., SN (z) = 0, it ”evolves” into a mixed state rN (z + Dz) under the
translation along z".

We are talking about the holographic screen, so there will always be an information about the existance of the neutron on the screen. Mass has gravity and so entropy, starting without any entropy whatsoever, means starting without mass. This is why he finds a term of shift on (16), proportional to the rest mass: a neutron was created! There should be none of such term since it should cancel out.

[crackjack]

I am unable to see how just a difference in the number of states between the slits, would lead to break down of interference pattern (as Motl says).

[MTd2]

I am unable to see how just a difference in the number of states between the slits, would lead to break down of interference pattern (as Motl says).

The states of the holographic sheet related with the diffraction are not entangled with those of the mass, that is, they are orthogonal subspaes. But the above article, not only entangles them, but also considers that mass can be set as 0 entropy.


Here is a case analog to that of the neutron experiment:

Suppose you want to calculate the entropy of a steam machine from its microstates. You can safely ignore the entropy of the quantum numbers of subatomic particles of the atoms, like those related to spin, color etc. There is no nuclear reaction involved, the entropy is already constant an maximal, what comes is comes out unchanged for practical purposes. Repeat the argument for the "quantum numbers of subatomic particles of the atoms" with "mass" and "steam machine entropy" with slit experiment, and there you have it.

[CHIKO-2010]

Yes, thanks. But the argument still does not hold because it supposes that the neutron cannot start with a zero entropy. On the top of page one:

"The above equations (10) and (11) tell us that even if we start with a pure neutron state
rN (z) at some z, i.e., SN (z) = 0, it ”evolves” into a mixed state rN (z + Dz) under the
translation along z".

We are talking about the holographic screen, so there will always be an information about the existance of the neutron on the screen. Mass has gravity and so entropy, starting without any entropy whatsoever, means starting without mass. This is why he finds a term of shift on (16), proportional to the rest mass: a neutron was created! There should be none of such term since it should cancel out.


All what matters is the entropy difference, eq. (11). SN (z) = 0 is not used to derive eq. (16). Also, your claim about mass and entropy is awkward - do you claim that massive pure states does not exist?

[MTd2]

Yes, you got a point. I never thought about that. In verlinde's gravity, mass cannot have entropy = 0, so no, there isn't a pure state of mass, because mass is a measure of disorder.

You see, temperature is a kind of measure of desorder, and in nuclear physics, it is commonly equated with temperature. Not that this is the same case here, but it follows along as a concept of disorder. And, as you know m=E, c=1. So, it makes sense that m= temperature!

[CHIKO-2010]

Yes, you got a point. I never thought about that. In verlinde's gravity, mass cannot have entropy = 0, so no, there isn't a pure state of mass, because mass is a measure of disorder. Hmm, good idea :)

You see, temperature is a kind of measure of desorder, and in nuclear physics, it is commonly equated with temperature. Not that this is the same case here, but it follows along as a concept of disorder. And, as you know m=E, c=1. So, it makes sense that m= temperature! :)


you are very wrong on this. within the special relativity there is an unambiguous definition of (inertial) mass. The inertial mass, according to experiments, is equal to the gravitational mass with very high accuracy. the concept of mass has certainly nothing to do with temperature and disorder.

[MTd2]

Verlinde is proposing a different theory of gravity, so SR and GR holds as diffusion equations. And certainly the mean deviation is very small. Just look at the size of the observable universe, and use that as more or less of the same magnitude of the holographic screen, which is much larger than 10^110plank^2.

And given that we are not exactly talking about GR or SR, but thermodynamical analogs, some things will cease to be states and rather, become statistical measures of other states, and in this case, it seems for me, that mass will become something like the temperature of a particle whereas the curvature will become something like the entropy.

[CHIKO-2010]

Verlinde is proposing a different theory of gravity, so SR and GR holds as diffusion equations. And certainly the mean deviation is very small. Just look at the size of the observable universe, and use that as more or less of the same magnitude of the holographic screen, which is much larger than 10^110plank^2.

And given that we are not exactly talking about GR or SR, but thermodynamical analogs, some things will cease to be states and rather, become statistical measures of other states, and in this case, it seems for me, that mass will become something like the temperature of a particle whereas the curvature will become something like the entropy.

Firstly, I do not think Verlinde has ever proposed the relation between mass and temperature as you put it here. Secondly, I think that precisely the fact that in Verlinde's theory there are nor pure states contradicts experiments, as it is pointed out in Mottl's essay and in the above paper

[MTd2]

Remember, if a neutron had a pure state, as you say, with S=0, it wouldn't be endowed with a gravitational field, so it wouldn't move anyway, or maybe it wouldn't exist, since it wouldn't be contained in an holographic screen. Note also that these are very rough analogies. A temperature does not need to be the same of that of a thermometer. It can be negative, if it is defined, for example, if it is defined in terms of spin of a lattice of ferromagnetic material.

[CHIKO-2010]

Remember, if a neutron had a pure state, as you say, with S=0, it wouldn't be endowed with a gravitational field, so it wouldn't move anyway, or maybe it wouldn't exist, since it wouldn't be contained in an holographic screen. Note also that these are very rough analogies. A temperature does not need to be the same of that of a thermometer. It can be negative, if it is defined, for example, if it is defined in terms of spin of a lattice of ferromagnetic material.


Well, again what you are saying follows from Verlinde's theory, and it looks like that its key predictions are not supported by observations

[MTd2]

One could formulate the statement. A particle with a 0 entropy of state is not represented on an holographic screen, so it doesn't exist. But that particle exist, thus Verlinde's gravity is false.

The contradiction can be solved, I think, like this: a particle exist, thus it has, at least, a relativistic mass. The minimum condition for existence of something, in Verlinde's gravity, is a bit of data on the holographic screen. The common denominator for the existence of both it is that a bit of data must have a relativistic mass. Thus, you cannot attribute, if you are working with this theory, with a particle without entropy.

[CHIKO-2010]

One could formulate the statement. A particle with a 0 entropy of state is not represented on an holographic screen, so it doesn't exist. But that particle exist, thus Verlinde's gravity is false.

The contradiction can be solved, I think, like this: a particle exist, thus it has, at least, a relativistic mass. The minimum condition for existence of something, in Verlinde's gravity, is a bit of data on the holographic screen. The common denominator for the existence of both it is that a bit of data must have a relativistic mass. Thus, you cannot attribute, if you are working with this theory, with a particle without entropy.

Why do you think that a particle in pure state cannot be represented on an holographic screen? This is certainly not correct! Think about of an ensemble of microstates, each individually having 0 entropy. I think the key point in Verlinde's theory is a difference in entropy between two holographic screens, that is, a state describing a neutron in the gravitational potential changes its entropy with the position. The case against Verlinde's theory is based on the arguments that precisely this basic feature of the theory is not supported by the quantum-mechanical experiments with neutrons.

[MTd2]

If you want to calculate the entropy, as defined by Verlinde, as it is the count of the very fundamental states, one cannot ignore the mass, by default, as a carrier of entropy by itself. If you ignore that, the theory will not work, as pointed out it the paper.

For me, the merit of that paper, if slightly changed, is to show that mass cannot be anything other than a measure of entropy. This is a great deal, not made clear by the author himself.

[CHIKO-2010]

If you want to calculate the entropy, as defined by Verlinde, as it is the count of the very fundamental states, one cannot ignore the mass, by default, as a carrier of entropy by itself. If you ignore that, the theory will not work, as pointed out it the paper.

For me, the merit of that paper, if slightly changed, is to show that mass cannot be anything other than a measure of entropy. This is a great deal, not made clear by the author himself.


I certainly cannot agree on this, and looks like we can't get a consensus...Anyway, thanks for the discussion. Cheers!

[crackjack]

The states of the holographic sheet related with the diffraction are not entangled with those of the mass, that is, they are orthogonal subspaes. But the above article, not only entangles them, but also considers that mass can be set as 0 entropy.


Here is a case analog to that of the neutron experiment:

Suppose you want to calculate the entropy of a steam machine from its microstates. You can safely ignore the entropy of the quantum numbers of subatomic particles of the atoms, like those related to spin, color etc. There is no nuclear reaction involved, the entropy is already constant an maximal, what comes is comes out unchanged for practical purposes. Repeat the argument for the "quantum numbers of subatomic particles of the atoms" with "mass" and "steam machine entropy" with slit experiment, and there you have it.

I have not read Verlinde's paper (just read Motl's critique). So, sorry, I could not make much out of your comment.
I will rephrase my question: Interference slowly starts breaking down if we differ the width of the slits etc, but how can I translate this (even heuristically) into a quantifiable statement based on differing number of states at the slits? In other words, how do we see that exp(10^15) (the value that Motl uses in his example) is huge enough for experimental detection of the pattern change?

[MTd2]

Motl's criticism is different from the paper of this thread. In the case of the paper, what is argued is the inadequacy of Verlinde's gravity to account for wave function evolution of massive because there is weird phase shift proportional to its relativistic mass. For me, this shift should not happen because the so called phase shift would be there from the beginning, yielding no difference at the end.

On Motl's article, he argues that since gravity is like a heat wave propagating on a solid, or aether, and if gravity disturbs a particle's path, the wave function would get phase random contributions from agitation of the "atoms" of this aether-like medium. This means that after a particles pass through a double slit, the two possible paths will interfere, on the projection screen, with random interference patterns.

That number he chose is the partition function a linear projection screen where we would count the states by a grid whose spacings would have the classical size of a neutron. He could had chose any other value, except infinite, but this is convenient due its intuitive experimental nature. When the "aether" is activated, that is, by running through different non inertial referentials(GR means being equivalent to apply a gravitational field), we clearly not expect to see anything.

[MTd2]

My own take on the latter criticism it is that if we are looking the problem from the space time point of view, we have to look at the minimum possible length. So, it shouldn't be a problem anyway, since there are 16 orders of magnitude to hide weird stuff.

[CHIKO-2010]

I have not read Verlinde's paper (just read Motl's critique). So, sorry, I could not make much out of your comment.
I will rephrase my question: Interference slowly starts breaking down if we differ the width of the slits etc, but how can I translate this (even heuristically) into a quantifiable statement based on differing number of states at the slits? In other words, how do we see that exp(10^15) (the value that Motl uses in his example) is huge enough for experimental detection of the pattern change?



As far as I can understand Mottl's argument, the interference pattern is destroyed due to the decoherence which is inevitable in Verlinde's theory. The initial neutron state (which supposed to be a mixed state with an entropy) sent towards the slits and the neutron states in two slits are described by the different number of microstates, they carry different entropy...in such situation neutron wave-functions decohere, and the factor exp(10^15) "measures" this decoherence. You simply do not see the interference pattern, which in contradiction with observations.

The paper of the thread is essentially based on the same argument. loosely speaking the bound states in the gravitational potential well can be viewed as standing waves formed due to the interference between incident neutron waves and the ones reflected from the mirror. These states are affected due to the entropy difference in the Verlinde's gravity, and the result contradicts experiments.

MTd2 is wrong supposing that the results of the paper are based on the assumption on the existence pure neutron states (with zero entropy). this is not true, as i wrote previously what is important is the entropy difference. Besides, the claim of non-existence of massive pure states is completely bizarre.

[CHIKO-2010]

P.S. According to MTd2 arguments photons as massless particle do not gravitate, which is certainly not correct -- light bends in the gravitational field.

[mitchell porter]

In Erik Verlinde's most recent talk (http://online.itp.ucsb.edu/online/joint98/verlinde2/), he essentially acknowledges that entropy can't be the whole story in his derivation of gravity, and in the second half starts looking for a property of the individual pure state which can play an analogous role.

[MTd2]

P.S. According to MTd2 arguments photons as massless particle do not gravitate, which is certainly not correct -- light bends in the gravitational field.

A photon bends space time and its path bended because it has mass. The type of mass is relativistic, as I said before. The rest mass is 0, though.

[CHIKO-2010]

A photon bends space time and its path bended because it has mass. The type of mass is relativistic, as I said before. The rest mass is 0, though.


What do you mean under the notion of "relativistic mass"? One of the key differences between GR and the Newtonian gravity is that the latter does not predict gravitation of a massless particles -- but this is NOT because the "relativistic mass" of photon approach to its rest mass = 0 in the non-relativistic limit! The photon gravitates in GR because of the tensorial nature of the gravitational field, while newtonian gravitational field (potential) is a scalar and it simply cannot couple to a massless vector field (photon). Again, gravitation of photon in no way depends on relativity, you may write perfectly relativistic theory of gravitation where photon does not gravitate (scalar theory of gravitation)

[MTd2]

Relativistic mass is the same as gravitational mass locally and in inertial frame, by the equivalence principle. And I am not referring anywhere to a non relativistic limit.

[CHIKO-2010]

Sorry, but photon mass is 0 in any (locally) inertial reference frame! That how the mass is defined -- in group theory language mass is an eigenvalue of the second casimir operator of the relativistic Lorentz group

[MTd2]

Alright, let's say that if a particle does not hold any energy, it doesn't exist.

[CHIKO-2010]

Alright, let's say that if a particle does not hold any energy, it doesn't exist.

Very funny statement -- can you imagine a material object which has no energy? in fact it is true statement - a quantum state without energy describes (again locally) vacuum states which has no real particles! But what this statement has to do with the holographic sreens and Verlinde's theory?

[czes]

George F.Smoot wrote in arXiv:1003.5952v1[hep-th] 31 Mar 2010 :
Chapter IV. It seems that having the temperature proportional to the curvature of space-time is a strange thing. We have entropy proportional to the inverse of the curvature (S~R^2) and temperature proportional to the curvature (T~1/R^2). The product is a constant for a fixed enclosed energy.
The Unruh temperature is T=h a /2 pi c k
here Smoot wrote:
T=hc/2 pi k R

It means a massive object curves the space-time and will perceive the same temperature as an accelerated object accordingly. If there is one particle with a rest mass it creates also a gravitational field around and there has to be a temperature. It will be also if the particle is alone in a Void. It means that it absorbs and emits quantum states from its space-time and oscillate due to Planck's black body radiation.

Does it mean each massive particle absorbs and emits quantum states due to its Compton wavelength in rest and shifted due to its relativistic energy ?
In the experiment there are neutrons in a motion and absorbed neutron in rest. Their wave functions has to interfere, I think.

[CHIKO-2010]

An isolated particle ("particle in a Void") does indeed emits and absorbs quantum states constantly, but these are the so-called virtual states, they are part of the vacuum, and as such do not create neither entropy nor temperature

[MTd2]

But what this statement has to do with the holographic sreens and Verlinde's theory?

That in the paper, the neutron initially has no energy whatsoever, so, it doesn`t exist.

[MTd2]

these are the so-called virtual states, they are part of the vacuum, and as such do not create neither entropy nor temperature

They do create entropy, as they all contribute to the actual mass. In fact, if you look how similar the path integral looks like a partition function, that the virtual particles are in fact the microstates of a particle. That also brings a problem, similar to what was raised by Motl, that due a limit bound on information, some virtual particles may be killed, just like interference fringes.

I personally think this is a possible advantage. That is, what if there are "hole" particles and they are responsible for dark matter?

[CHIKO-2010]

That in the paper, the neutron initially has no energy whatsoever, so, it doesn`t exist.

Could you please be more specific where in the paper you find that "the neutron initially has no energy"?

[CHIKO-2010]

They do create entropy, as they all contribute to the actual mass. In fact, if you look how similar the path integral looks like a partition function, that the virtual particles are in fact the microstates of a particle. That also brings a problem, similar to what was raised by Motl, that due a limit bound on information, some virtual particles may be killed, just like interference fringes.

I personally think this is a possible advantage. That is, what if there are "hole" particles and they are responsible for dark matter?


Sorry, but what you have written above does not make any sense! You seems are confused with some basic stuff of quantum field theory.

[MTd2]

Could you please be more specific where in the paper you find that "the neutron initially has no energy"?
In the paper, a neutron was set with zero entropy. But if you are dealing with calculations inside the theory of verlinde, all entropy must be taken into account, including the one from the mass. So, the neutron cannot possibly be started with a 0 entropy because that would be ignoring the entropy of the mass and given that we are talking about gravity, gravity cannot be forgotten because it is the main part of the problem.

[MTd2]

Sorry, but what you have written above does not make any sense! You seems are confused with some basic stuff of quantum field theory.

Verlinde`s theory does not look like QFT for me.

[CHIKO-2010]

In the paper, a neutron was set with zero entropy. But if you are dealing with calculations inside the theory of verlinde, all entropy must be taken into account, including the one from the mass. So, the neutron cannot possibly be started with a 0 entropy because that would be ignoring the entropy of the mass and given that we are talking about gravity, gravity cannot be forgotten because it is the main part of the problem.

1. please read the paper more carefully. Neutron is NOT set with zero entropy in the paper.

2. More importantly, the energies corresponding to neutron states in eq. (18) are given in eq. (17). They all are non-zero!

[CHIKO-2010]

Verlinde`s theory does not look like QFT for me.

You commented on virtual particles producing entropy -- if you are talking about thermodynamics, what the virtual particles have to do with it? Virtual particles do not exist in classical physics, they do not exists even in quantum mechanics

[MTd2]

Although there is a typo in the line above eq. 15 (it uses eq. 15 to find eq. 15), I cannot agree with eq. 15. It assumes that the entropy increases to mc, from 0, using eq. 12.

[MTd2]

You commented on virtual particles producing entropy -- if you are talking about thermodynamics, what the virtual particles have to do with it?

Think of processes with the same outcome, but with different virtual processes, as like analogues of degenerate sates. It is just that since Verlnde`s gravity is not unitary, some of these processes are destroyed.

[CHIKO-2010]

Although there is a typo in the line above eq. 15 (it uses eq. 15 to find eq. 15), I cannot agree with eq. 15. It assumes that the entropy increases to mc, from 0, using eq. 12.


I think the remark above eq. 12 is indeed confusing. In deriving eq. 15 you do not need to assume that a state at z is a pure state, it can be a mixed state as well. Eq 12 is just a generic equation which tells you how the density matrix changes under the translation along z-direction. So, the end result does not depend on the assumption on the existence of pure neutron state, i.e. absolute entropy are not important in deriving (15) only the entropy difference given by eq. (11).

[MTd2]

I checked the origin of eq. 11, that's eq. 3.6 of Verlinde's paper.

Where is the holographic screen, for you? For me, it is of order ~10billion light years away, which is 10^23.The compton length is 10^-15, so the suppression, in 8, factor is about exp(-5*10^-8), that is, 50 parts in one billion.

BTW, now, I agree with you, as far as having 0 entropy, and gaining an entropy proportional to the relativistic mass, . It happens by crossing the holographic screen. It is an non causal region, so it is the same as the particle didn't exist.

[CHIKO-2010]

[QUOTE=MTd2;2913006]I checked the origin of eq. 11, that's eq. 3.6 of Verlinde's paper.

Where is the holographic screen, for you? For me, it is of order ~10billion light years away, which is 10^23.The compton length is 10^-15, so the suppression, in 8, factor is about exp(-5*10^-8), that is, 50 parts in one billion.


I guess z in (18) must be between the absorber and the mirror, for z higher than the absorber neutrons are not passing the slit, this is just due to the experimental setup. I do not understand where did you get ~10billion light years (?!) from when you just need to reproduce local gravitational field of Earth

[Fra]

If you judge Verlindes paper as an input among the sea of other papers I personally thing it's good. But even though I belong to those that think thta ALL forces eventually should be understood as a generalised form for "entropic" processes, I think Verlindes paper rather raises more questions than it answers (what is the origin and status of the holographic principle etc) are good ones, I like his paper.

I personally think some of the underlying ideas I read of verlinde such as he expressed in his original paper

"The universality of gravity suggests that its emergence should be understood from general principles that are independent of the specic details of the underlying microscopic theory. In this paper we will argue that the central notion needed to derive gravity is information. More precisely, it is the amount of information associated with matter and its location, in whatever form the microscopic theory likes to have it, measured in terms of entropy. Changes in this entropy when matter is displaced leads to an entropic force, which as we will show takes the form of gravity. Its origin therefore lies in the tendency of the microscopic theory to maximize its entropy. The most important assumption will be that the information associated with a part of space obeys the holographic principle [8, 9]."

I share the first parts, but this raises questiosn such as:

Where is the observer, and how does he account for the fact that entropy must be relative?
Also what inferences leads a generic observer to infer the holographic principle? and how can this be formulated in an intrinsic sense?

I think Verlindes quest for understanding gravity from general principles of information processing is sound, but he assumes too much baggage, some of it that may even also be wrong. But I don't think that invalidates the intent.

Maybe instead of rejecting the entire idea of inductive processes in physics based on incomplete first steps, maybe we should instead keep asking the deeper questions that Verlindes paper feeds.

How does an inside oberver construct intrinsic measures of "amount of information" stored say in an unknown environment?
How does the notion of "location" emerge from this picture?
What is "matter" in terms of this picture?
What status does the holographic principle have in terms of these much more basal terms?

I think we have to distinguish between two views, an observer beeing ITSELF living inside a strongly dynamical gravitational field, or an observer that from a safe distance or static field, observers gravitational interactions between subsytems in it's own environment. I think this relates to theories that contain gravity as an interaction on part with the others, and thoese theories that doesn't. IT seems clear to me that the second scenario does put gravity on par with any other interaction in priciple. But the first picture does not.

Similar things can be said about constructing measures of missing information, it's not a priori obvious, that two observers measures the amount of information the same - then the question is what is the consequence of this disagreement?

I think questions of these kinds are all questions that indirectly come out of Verlindes paper. Verlindes does not answer them, but I think they are good. So I don't like some of the reactions that somehow suggest that verlinde would be some crackpot because it's easy to see that he lacks all answers. That's a too simple reaction.

/Fredrik

[CHIKO-2010]

Dear Fredrik,

you are asking interesting questions concerning the original proposal by Verlinde. However, the points you have mentioned are in essence methaphysical. I think this is not how physics as an empirical science works. A given physical hypothesis (idea, model) must be able to describe certain observational facts. If it does, it becomes a theory which maybe subsequently refined, improved etc. If deductions made out of the basic idea fail to explain observations, the idea is declared false...there are many such false ideas in the history of physics much much more than the correct ones...

So the question in this particular discussion is that whether Motl's objections and the related arguments in the paper indeed show that Verlinde's idea on entropic gravity is false. I tend to think they do, because those objections are based on avery basic idea by Verlinde - gravity is due to the difference in entropy of a particle related with its position. The questions related with detailed physics of holographic screens, observers etc are irrelevant here, in my opinion.

[Fra]

So the question in this particular discussion is that whether Motl's objections and the related arguments in the paper indeed show that Verlinde's idea on entropic gravity is false. I tend to think they do

Ok that point is well taken. You're right that's the specific question here. And I admit that if we define the question as such, it's probably false. But my only point was that I feel that's somehow a too simple question & conclusion.

My point is that, although Verlindes idea seems imperfect, I think it's more interesting to try to discuss how it can be improved, rather than trying to just proove that it's false.

gravity is due to the difference in entropy of a particle related with its position. The questions related with detailed physics of holographic screens, observers etc are irrelevant here, in my opinion.

I disagree. I merely question that then notions of entropy is more complex than verlinde admits, but I think the underlying idea is not wrong. It may be wrong because the measures of information and the holographic principle is wrong. Both these things are IMHO related to the careless treatment of the observer, because the observer is also the home of the theory in my view.

So while it seems probably that the specific attempt of verlinde is flawed, there is something about the idea that I think is right. And since ideas in this direction are unfortunately rare, I show my support even though his first attempt is wrong. I see more than a flawed theory here - I see a way of reasoning that can generate theories.

/Fredrik

[MTd2]

I do not understand where did you get ~10billion light years (?!) from when you just need to reproduce local gravitational field of Earth

Well, now I see where why we were disagreeing. Sure, the neutron can be made with 0 entropy, but I never thought that you were positioning exactly or behind the holographic screen, since you were talking about an experiment actually done.

Sure, your equations are right then. All your calculations are OK, but the holographic screen, that z, that you based your eq. 11 from Verlinde's paper, is a cosmological idea. And that holographic screen is not his idea, he cites Wald for that. Raphael Bousso also cited and used that holographic screen, which he identifies with the apparent horizon of the FRW model. This model is by no means local, not even any of its ancestors, except for the thermodynamical gravity, because it uses input, at all points, from the past light cone, following Wald's idea.

There are 2 z's, actually, on your equation, but both sits at the same line. One that measures the distance from the center of the earth and other to the holographic screen. Since you are doing a differential equation, it doesn't really matter that much where you put the ground state. It matters, though, in the end, where you put the actual values.

[MTd2]

My calculation above is wrong, it should be a exp(-5*10^38), much stronger than yours, but all intervals of integration should be changed anyway. So this value is moot anyway.

[czes]

Fredrik wrote above that gravity has to be derived from the quantum information. I think it is in the general Wheeler's idea that the future physics will be physics of the information.

Could we say the pure quantum state is something like a virtual particle ?
When I wrote the massive real particle alone has its environment the gravitational field, the virtual particles-antiparticles. The real massive particle absorbs and emits the virual p-a and therefore it oscillate. The virtual p-a hasn't an entropy and temperature but the massive real particle has. It is in a rest if the absorption=emission. it means the entropy and temperature remains on the same level.

If the absorption is faster than the emission the massive particle accelerate (negentropy) due tu Unruh effect.
If the emission is faster the massive particle gets slower (entropy increases) temperature goes down.

The gravitational field could be here as a field of the virtual plasma (virtual particles-antiparticles). The virtual p-a appear and disappear due inversely proportional to the squared distance from the massive particle. Therefore the location is important.
Verlinde's entropy is not like Boltzman's entropy in a gas. The virtual p-a due to Unruh are not real but the calculation is similar.

I have the calculations using the Compton wavelength and not the Boltzmann constant and have the same results.

[MTd2]

Given the cosmological aspect of this theory, we have to look for ways to find what went wrong in the above derivation. We know that the entropy of a particle at the particle horizon is 0. So, there must be a boundary condition for the U operator, otherwise, this problem will look like it was done in a universe a little bit larger than Earth, where the absober is a few micrometers away from the edge of the universe.

[CHIKO-2010]

Given the cosmological aspect of this theory, we have to look for ways to find what went wrong in the above derivation. We know that the entropy of a particle at the particle horizon is 0. So, there must be a boundary condition for the U operator, otherwise, this problem will look like it was done in a universe a little bit larger than Earth, where the absober is a few micrometers away from the edge of the universe.


There are no cosmological issues in deriving Newton's law within Verlinde's theory! newton's force is a local force, which presumes that the Universe is static locally. newton's law of gravity does not hold on cosmological scales. To describe gravitating system neurton-Earth, the relevant quantity is the entropy change due to the change in the position of a test particle (neutron). That is, the net result depends on the entropy gradient (see e.g. Verlinde's eq. 3.7 for the force) which, according to verlinde's eq. 3.6, is constant. Your objections/intepretations, therefore, are invalid.

[CHIKO-2010]

P.S. Note that Verlinde's holographic sreens have nothing to do with cosmological, black hole etc horizons

[CHIKO-2010]

[QUOTE=czes;2913753]

Could we say the pure quantum state is something like a virtual particle ?
When I wrote the massive real particle alone has its environment the gravitational field, the virtual particles-antiparticles. The real massive particle absorbs and emits the virual p-a and therefore it oscillate. The virtual p-a hasn't an entropy and temperature but the massive real particle has. It is in a rest if the absorption=emission. it means the entropy and temperature remains on the same level.

For futher clarification: Pure state can describe both virtual and real particles. real massive (quantum-mechanical) particle which is described by pure state has no entropy and no temperature. The classical particle (or field) can be viewed as a incoherent collection of many (statistically large number of) quantum-mechanical states and only that object carries entropy!



The gravitational field could be here as a field of the virtual plasma (virtual particles-antiparticles). The virtual p-a appear and disappear due inversely proportional to the squared distance from the massive particle. Therefore the location is important.
Verlinde's entropy is not like Boltzman's entropy in a gas. The virtual p-a due to Unruh are not real but the calculation is similar.

In certain sence you are right. In field-theoretic approach newton's law (potential) can be derived as an exchange of virtual gravitons bewteen two gravitating real particles (weak gravity approximation + take non-relativistic limit). however for isolated particle (take the second particle to infinity) the gravitons are essentially on-shell, they are real -- these describe gravitational radiation (waves)

All the above is the very standard view on gravity as well as other interactions, say electromagnetism etc...Verlinde's theory is radically different though. There are NO gravitons there neither virtual nor real

[qsa]

Given the cosmological aspect of this theory, we have to look for ways to find what went wrong in the above derivation. We know that the entropy of a particle at the particle horizon is 0. So, there must be a boundary condition for the U operator, otherwise, this problem will look like it was done in a universe a little bit larger than Earth, where the absober is a few micrometers away from the edge of the universe.

verlide has discussed this issue in the starting pragraphs in his
paper


http://arxiv.org/PS_cache/arxiv/pdf/1001/1001.0785v1.pdf


""Gravity dominates at large distances, but is very weak at small scales. In fact, its
basic laws have only been tested up to distances of the order of a millimeter. Gravity is
also considerably harder to combine with quantum mechanics than all the other forces.
The quest for unifcation of gravity with these other forces of Nature, at a microscopic
level, may therefore not be the right approach. It is known to lead to many problems,
paradoxes and puzzles. String theory has to a certain extent solved some of these, but
not all. And we still have to figure out what the string theoretic solution teaches us""

I think this is related to my thread which seems nobody wants to touch.

http://www.physicsforums.com/showthread.php?t=432711

[MTd2]

There are no cosmological issues in deriving Newton's law within Verlinde's theory! newton's force is a local force, which presumes that the Universe is static locally. newton's law of gravity does not hold on cosmological scales.

Quantum Mechanics is not a local theory so you will have to look for boundary values and sum over all space if you want to do it right. For example,the operator U is expanded linearly as its border conditions at the holographic screen were irrelevant. In reality, U should be written like U=Aexp(...), where A is a function that makes U goes smoothly to 0 at the screen and to the maximum value of entropy at r=0.

How that is defined, is up to cosmological considerations. But given the smoothing conditions, it must be such that for local boosts, near the center, the value of the constant k, on eq. 13, is almost null. Otherwise, one is using "unfair" boundary conditions to rule out the theory.

[qsa]

Ok that point is well taken. You're right that's the specific question here. And I admit that if we define the question as such, it's probably false. But my only point was that I feel that's somehow a too simple question & conclusion.

My point is that, although Verlindes idea seems imperfect, I think it's more interesting to try to discuss how it can be improved, rather than trying to just proove that it's false.



I disagree. I merely question that then notions of entropy is more complex than verlinde admits, but I think the underlying idea is not wrong. It may be wrong because the measures of information and the holographic principle is wrong. Both these things are IMHO related to the careless treatment of the observer, because the observer is also the home of the theory in my view.

So while it seems probably that the specific attempt of verlinde is flawed, there is something about the idea that I think is right. And since ideas in this direction are unfortunately rare, I show my support even though his first attempt is wrong. I see more than a flawed theory here - I see a way of reasoning that can generate theories.

/Fredrik

the paper by joakim helps to clarify many issues, it should be a very interesting read. It has been listed before in PF but I think a close examination is warranted here.

http://arxiv.org/PS_cache/arxiv/pdf/1003/1003.1262v3.pdf

[CHIKO-2010]

[QUOTE=MTd2;2914474]Quantum Mechanics is not a local theory so you will have to look for boundary values and sum over all space if you want to do it right. For example,the operator U is expanded linearly as its border conditions at the holographic screen were irrelevant. In reality, U should be written like U=Aexp(...), where A is a function that makes U goes smoothly to 0 at the screen and to the maximum value of entropy at r=0.

What are you talking about? U as it is defined in the paper is the standard operator of translations which is valid in quantum mechanics! acting on a state \psi(z) it transforms the state into a new state \psi(z+\delta z) (\delta z can be counted as infinitesimally small). Again, it is completely irrelevant what are the entropies of these two states \psi(z) and \psi(z+\delta z). what is relevant is an entropy difference. QM is nonlocal theory in ceratin sense but in this particular case we are talking about gravitational potential energy of neutron-Earth system which depends only on local coordinate z.

[CHIKO-2010]

P.S. The only physical boundary condition on the wave-function of neutron is \psi(z=0)=0 (if the mirror is treated as a perfect reflector)

[MTd2]

U as it is defined in the paper is the standard operato

A standard operator that is non unitary...

[CHIKO-2010]

A standard operator that is non unitary...

It is not unitary only for the specific problem: neutron-earth system where the gravitational interactions are treated according to Verlinde. This follows from the entropic description of gravity and falsified by the observations. your heroic attempts to modify U on cosmological scales etc are wrong. well, you could try to modify quantum mechanics also -- the claim in the paper is only valid if the usual quantum mechanical description of the given problem is correct, of course.

[MTd2]

well, you could try to modify quantum mechanics also -- the claim in the paper is only valid if the usual quantum mechanical description of the given problem is correct, of course.

This is what is done in the paper too, it is set up its own axioms to modify quantum mechanics. There are other ways too, like, I sugested, setting up a kappa modification dependent on space and/or time.

[MTd2]

An holographic surface is a remain from a very limited attempt to see common aspects of GR and QM, which is the surface of a black hole quantized by a discreet quantity. This was later generalized by Wald (past cone only) and Bousso to any surface that represented causal discontinuity.

So, if one is claiming an holographic surface within a Newtonian context, that person is imposing quite artificially a causal discontinuity. For low gravitational fields, that's ok, but if one is trying to get a quantization in this same context, some GR low energy limit must be taken or considered. The reason for this it is that the integration will include places where gravitational distortions are very important, like the particle horizon or apparent horizon.

[CHIKO-2010]

This is what is done in the paper too, it is set up its own axioms to modify quantum mechanics. There are other ways too, like, I sugested, setting up a kappa modification dependent on space and/or time.


Your suggestion of nullifing kappa in eq. 13 would mean that the gradient of entropy for free falling neutron in the gravitational field of Earth is zero. According to Verlinde this means that neutron does not gravitate at all (i.e. free fall acceleration g=0) -- you will end up contradicting the experiments anyway

[CHIKO-2010]

P.S. The parameter kappa is entirely determined by the entropy gradient which is a constant (see e.q. 3.6 of Verlinde) i.e. it does not depend on space and time

[MTd2]

What I meant it is that the deficit in the non unitarity does not have to be equal to the gradient of entropy.

[CHIKO-2010]

What I meant it is that the deficit in the non unitarity does not have to be equal to the gradient of entropy.


Well, non unitarity is due to the fact that netron states have different entropy at different positions, and the entropy gradient in turn defines the strength of gravity. I do not see any way how you can avoid this.

[Fra]

the paper by joakim helps to clarify many issues, it should be a very interesting read. It has been listed before in PF but I think a close examination is warranted here.

http://arxiv.org/PS_cache/arxiv/pdf/1003/1003.1262v3.pdf

Thanks, I'll print and read that during the week. Just judging from the title though, what I personally think is not quite that "gravity and holograhpy follows from QM". What I think is that gravity follows from a interacting inference systems. Which can be thought of as a more generalized form of "measurement theory".

If we characterize QM as inference containing non-commutative structures, then the additional constraint we need to add, is the complexity bound. QM as it stands more corresponds to either a static non-interacting observer, or possibly an equilibrium condition. When an observer gains or looses mass at a rate that is significant relative to the observed processes, QM as we know breaks down IMO. This is why I think the framework needs to allow evolving observers. Real observing systems aren't static. And of course there is neither a static description of their dynamics expcet as partial descriptions by a third observer interacting with it.

Part of this also means that two observers generally rate the "entropy" differently. And there is no observer-invariant transformation except as local equilibrium conditions. Therefor I think the ultimate entropic interactions necessarily must reflect the observes action and evolution as well, not just be an objective false description of two interacting subsystems.

It's indeed popular to dismiss these problems as metaphysical but that's IMO just like sticking the head in the sand for a difficult problems. No progress will be made unless we try to face the problems.

/Fredrik

[czes]

Your suggestion of nullifing kappa in eq. 13 would mean that the gradient of entropy for free falling neutron in the gravitational field of Earth is zero. According to Verlinde this means that neutron does not gravitate at all (i.e. free fall acceleration g=0) -- you will end up contradicting the experiments anyway

Does it mean that according to Verlinde gravity is entropic force but gravitational field is not quanized because there are not gravitons ?
Therefore due to Verlinde the slit can't be opaque for neutrons ?

[CHIKO-2010]

Does it mean that according to Verlinde gravity is entropic force but gravitational field is not quanized because there are not gravitons ?
Therefore due to Verlinde the slit can't be opaque for neutrons ?


It is true that in Verlinde's gravity there are no gravitons as fundamental degrees of freedom. However, the contradiction with the experiments discussed in the paper is not due to the fact that gravity is not quantized. This is a problem of quantum-mechanical particle moving in the CLASSICAL gravitational field of Earth. The probelm is due to the fact that this classical gravitational force acting on neutron has intrinsically entropic origin, i.e. its emerges only due to the change in the entropy of neutron states at different positions. That is a neutron state \psi(z) and \psi(z+\delta z) do not "match" unitarily, loosely speaking something gets lost/gained going from \psi(z) to \psi(z+\delta z). Solutions which reflect this changes compared to the usual description of the problem are obviously different, so that the predictions are not agree with observations. The experiments, in turn, are in reasonably good agreement with the standard description.

[czes]

It is true that in Verlinde's gravity there are no gravitons as fundamental degrees of freedom. However, the contradiction with the experiments discussed in the paper is not due to the fact that gravity is not quantized. This is a problem of quantum-mechanical particle moving in the CLASSICAL gravitational field of Earth. The probelm is due to the fact that this classical gravitational force acting on neutron has intrinsically entropic origin, i.e. its emerges only due to the change in the entropy of neutron states at different positions. That is a neutron state \psi(z) and \psi(z+\delta z) do not "match" unitarily, loosely speaking something gets lost/gained going from \psi(z) to \psi(z+\delta z). Solutions which reflect this changes compared to the usual description of the problem are obviously different, so that the predictions are not agree with observations. The experiments, in turn, are in reasonably good agreement with the standard description.

I think, a neutron continually absorbs and emits the virtual particles-antiparticles from the gravitational field. If the virtual p-a are just non-local quantum information interactions between the massive object and the rest of the Universe. Each massive particle absorbs and emits (oscillate) due to its Compton wavelength. Therefore the density of the appearing and disappearing virtual p-a is inversely proportional to the distance from the massive object.

The neutron increases the frequence of the oscillation when it approaches the Earth because it absorbs more than emits due to the density of the virtual p-a. It becomes accelerate towards the massive object because it gains more information in this direction.
The fundamental information could be Planck length contraction and Planck time dilation for each non-local quantum information due to Compton wavelength of each particle.

Graviton would be here just a shift of the spacetime of the Planck length and time due to interaction with this non-local information due to Compton wavelength.

I have calculations for gravitational time dilation using the Compton wavelength structure.
Personally I do not use entropy in that calculation but Verlinde's calculations shows a similar effect.

[CHIKO-2010]

I think, a neutron continually absorbs and emits the virtual particles-antiparticles from the gravitational field. If the virtual p-a are just non-local quantum information interactions between the massive object and the rest of the Universe. Each massive particle absorbs and emits (oscillate) due to its Compton wavelength. Therefore the density of the appearing and disappearing virtual p-a is inversely proportional to the distance from the massive object.

The neutron increases the frequence of the oscillation when it approaches the Earth because it absorbs more than emits due to the density of the virtual p-a. It becomes accelerate towards the massive object because it gains more information in this direction.
The fundamental information could be Planck length contraction and Planck time dilation for each non-local quantum information due to Compton wavelength of each particle.

Graviton would be here just a shift of the spacetime of the Planck length and time due to interaction with this non-local information due to Compton wavelength.

I have calculations for gravitational time dilation using the Compton wavelength structure.
Personally I do not use entropy in that calculation but Verlinde's calculations shows a similar effect.


Frankly speaking, I cannot make any sense from your post. you seems have your own theory of gravitational interactions, which is hard to comprehand (at least for me) from your short writing. If your work is available on-line/published plz give a reference and I'll read it. Thanks

[CHIKO-2010]

P.S. Did Verlinde calculate time dilation in his theory?

[czes]

Frankly speaking, I cannot make any sense from your post. you seems have your own theory of gravitational interactions, which is hard to comprehand (at least for me) from your short writing. If your work is available on-line/published plz give a reference and I'll read it. Thanks

GRAVITATIONAL TIME DILATION
My calculations are based on an equation:
lp / l x ) * (lp / l y ) = -a Fg / Fe

where:
lp * lp – Planck length squared = hG/c3
l x , l y –Compton wave length of two interacting particles x,y l= h/mc
a – alfa=ke^2 /hc = fine structure constant
Fg – Gravitational Newton's interaction Fg = Gm(x) m(y) /r^2
Fe - Electrostatic Coulomb interaction Fe = ke^2 /r^2


Gravitational time dilation is the effect of time passing at different rates in regions of different gravitational potential; the lower the gravitational potential (closer to the center of a massive object), the more slowly time passes. Albert Einstein originally predicted this effect in his theory of relativity and it has since been confirmed by tests of general relativity.

In quantum gravity time is created by a number of quantum events. Each event results with a Planck's time dilation and therefore we perceive a flow of the time. Time doesn't exist as an independent fundamental property or phenomenon.

We measure a distance and a time by a constant speed of light as a constant number of the quantum events which are passed by a photon N= R/lp.

A distance and time become contracted by the number of Planck's units when there is an additional non-local information from a real massive particle with its Compton wave length l= h/mc . We calculate the interference of the information from the direction of the observer and from the direction of the massive particle as a vector sum in a triangle.

As we showed above N=M/m particles cause (M/m) [(lp /(ly/2) )] length contraction and proportional time dilation where ly is a Compton wave length information of the massive particle perpendicular to the information of the observer in vacuum.

Therefore time is a sum :

t(f)^2 (R/lp) = t(0)^2 (R/lp) + t(f)^2 (M/m) [(lp /(ly/2) )]

t(0)^2 (R/lp) = t(f)^2 {(R/lp) - (M/m) [(lp /(ly/2) )]}

where:
lp * lp – Planck length squared = hG/c^3
Compton wave length lp=h/mc
After substitution we receive a well known equation for gravitational time dilation:
t(0)^2= (1-2GM/Rc^2 )

http://www.hlawiczes1.webpark.pl/gravastar.html

I didn't see Verlinde calculated time dilation but he received Holographic Principle resolution
S=A/4 l(p)^2

[MTd2]

Well, non unitarity is due to the fact that netron states have different entropy at different positions, and the entropy gradient in turn defines the strength of gravity.

Yes, one has to define a dependence on entropy for k. It does not have to be linear, one can define k in whatever way you want, with the following constrains: map 0 at the cosmological horizon to maximum entropy at the origin, smoothly increasing until. It will not affect the potential, since both have different dependencies on the entropy.

[CHIKO-2010]

Yes, one has to define a dependence on entropy for k. It does not have to be linear, one can define k in whatever way you want, with the following constrains: map 0 at the cosmological horizon to maximum entropy at the origin, smoothly increasing until. It will not affect the potential, since both have different dependencies on the entropy.


Why one has to map something on the cosmological horizon when describing neutron-earth system? Besides, it is just against the holographic conjecture to assume that the entropy on the cosmological horizon is 0 and entropy "at the origin" (center of earth?!) is maximum! Do you really think that these "boundary conditions" are natural?

Do you agree that the generator of z-translation P must be non-hermitian? If yes, the rest
of the derivation given in the paper is actually very simple. First you parameterize non-hermitian operator P as P=p+ix, where both p and x are hermitian operators. then use eq.12, the definition of entropy eq (7) and Verlinde's equation (11). you will get x=2Im\kappa given by eq. (15).

If you want to use instead of linear operators non-linear operators and all that kind of nonsense, be my guest. But note that the algebraic structure of QM in the paper is not modified, that is [z,p]=ih, [p,p]=[z,z]=0, while with your proposal I am sure you will get even more dramatic modification of QM. If you have a concrete proposal of such a modification plz let me know and we can discuss it further. If not, it does not make sense to continue.

[MTd2]

Why one has to map something on the cosmological horizon when describing neutron-earth system? Besides, it is just against the holographic conjecture to assume that the entropy on the cosmological horizon is 0 and entropy "at the origin" (center of earth?!) is maximum! Do you really think that these "boundary conditions" are natural?

For Verlinde's gravity they surely natural. As I explained above, the holographic screen is a reminiscent of quantum theory using an asymptotic spacial region with a causal discontinuity. It doesn't exist in newtonian regime, so if one wants to quantize, a necessary step is a suitable function which works well in a reasonable cosmology.

The entropy of an object of the bulk goes to zero when it approaches the holographic screen, not the holographic screen itself. The object needs less bits to represent it.

[CHIKO-2010]

F

The entropy of an object of the bulk goes to zero when it approaches the holographic screen, not the holographic screen itself. The object needs less bits to represent it.

Ok. I somehow thought you are talking about the entropy of holographic screens in your previous post. Your objection does not make sense to me anyway. I am repeating again - the net result depends on the entropy gradient, \partial S/\partial z which is constant throught space and time, according to Verlinde.

I simply cannot "digest" your remark that for the quantization of neutron in the classical gravitational field of Earth you necessarily need to consider cosmological model. I do not want to argue about this anymore, I won't be able to understand your arguments anyway.

[MTd2]

It is not possible to affirm that the relation between kappa and the entropy is linear. It must be considered the general relativistic for that given that, the integration domain goes to the holographic screen, where gravitational effects are strong, and so entropy. Linearity is not expected. One thing is certain, unitarity goes to one as one gets close to the observer, but how it goes to one, it is another story. It could very well to 1 a few inches from the holographic screen and remain constant from billions of light years.

[CHIKO-2010]

It is not possible to affirm that the relation between kappa and the entropy is linear. It must be considered the general relativistic for that given that, the integration domain goes to the holographic screen, where gravitational effects are strong, and so entropy. Linearity is not expected. One thing is certain, unitarity goes to one as one gets close to the observer, but how it goes to one, it is another story. It could very well to 1 a few inches from the holographic screen and remain constant from billions of light years.


For the derivation of Newton's law there is no need to consider strong gravity. A holographic screen in Verlinde's theory can be any equipotential surface that embodies the gravitating mass M. Agan, to describe classical gravitational field produced by Earth at a distance R+r from the center of earth you need to consider holographic screen at R+r. This is how Verlinde derives his gravitational potential. Now drop in this potential a neutron (a test particle). If you consider the neutron as a classical particle everything follows Verlinde.

However, when one considers neutron as a quantum mechanical particle you are start saying that now we have to move screen to the cosmological horizon. then you suggest that \kappa is non-zero only "a few inches" from the screen and zero (or almost zero) everywhere else. The straightforward conclusion from your theory is: since \kappa is 0 near Earth, the translation operator is unitary, and, as a result, there is no gradient of entropy and hence nor gravitational field acting on neutron (near Earth). your theory fails to explain experiments, it looks like it does not have a classical limit as well.

I think your confusion boils down to a very simple fact -- you resist to recognize that classical gravitational field of earth acting on neutron states is a local field

[CHIKO-2010]

P.S. And aslo, plz be a little bit more accurate in your definitions, it sometimes very hard to underdtand what are you talking about. E.g., what does it mean "unitarity goes to 1"?

[MTd2]

If one is looking for the deficit in unitarity, one is surely questioning the limits of "information processing". That is given by the biggest holographic screen possible, the one given by the apparent horizon of the observable universe. This is a consequence of QM taking all possible combinations, paths, etc, which is limited by the holographic screen, which is always an asymptotic surface with causal discontinuity. The classical problem does not have this issue, which is why one can work with the holographic screen that most suits the problem.


since \kappa is 0 near Earth, the translation operator is unitary, and, as a result, there is no gradient of entropy and hence nor gravitational field acting on neutron (near Earth). your theory fails to explain experiments, it looks like it does not have a classical limit as well.

Not quite, since the depedey of kappa of the entropy is sligh. For example: K= exp(-constant*((radius of the earth)/radius of the observable iniverse))*(gradient of entropy)). May not be quite this, but this is the idea.

[MTd2]

P.S. And aslo, plz be a little bit more accurate in your definitions, it sometimes very hard to underdtand what are you talking about. E.g., what does it mean "unitarity goes to 1"?

It means that your lab experiments conserve quantum probabilities to amazing accuracy, where as those near the holographic screen might vanish or creates states or whole particles, which means crossing the horizon.

[CHIKO-2010]

Not quite, since the depedey of kappa of the entropy is sligh. For example: K= exp(-constant*((radius of the earth)/radius of the observable iniverse))*(gradient of entropy)). May not be quite this, but this is the idea.[/QUOTE]


Ok. let's be more specific. Could you please answer the questions below, just want to exclude that we have disagreement on the level of technicalities:

1. Do you aregree with eq. (7)?
2. Do you agree with eq. (13)?
3. I suppose you agree with (11).

If 1,2,3 are yes, then why do you doubt in 15? it just follows from the above eqs. if you do not agree with eather 1,2,3 please explain how do you think they must be modified.

[CHIKO-2010]

It means that your lab experiments conserve quantum probabilities to amazing accuracy, where as those near the holographic screen might vanish or creates states or whole particles, which means crossing the horizon.

Sorry, but probabilities are conserved (in time of course) in the paper -- the time evolution is unitary (hamiltonian hermitian). The type of unitarity conservation you are talking about has been addressed very carefully by Verlinde, at classical (thermodynamical) level it is related with the reversability of the underlying thermodynamic process that ensures the derived Newton's force is conservative

[MTd2]

1. Do you aregree with eq. (7)?
2. Do you agree with eq. (13)?
3. I suppose you agree with (11).


Yes, yes, yes. For 15, mc*logistic function, with 0 at r=0, and a non zero value at r=holographic screen. But one very steep, quite a step function.

"The type of unitarity conservation you are talking about has been addressed very carefully by Verlinde, at classical (thermodynamical) level it is related with the reversability of the underlying thermodynamic process that ensures the derived Newton's force is conservative"

Indeed, precisely these that I am talking about. If you release an object near the ground, you will see it unitarity, but not if you observe a similar experiment, from earth, done a few seconds or so after the big bang, which is near the holographic horizon in our past cone. You will get the results similar to yours. He did not address precisely the question of how much unitary would change.

[CHIKO-2010]

[QUOTE=MTd2;2915565]Yes, yes, yes. For 15, mc*logistic function, with 0 at r=0, and a non zero value at r=holographic screen. But one very steep, quite a step function.


If yes, yes, yes than 15 should be correct as well - its simple algebra. I am puzzled where does this "logistic function" come from? Ok, I think you do not have answer on this question right now. Let me now if you will be able to calculate your "logistic function", for me it is = 1. :wink:

[MTd2]

If yes, yes, yes than 15 should be correct as well - its simple algebra. I am puzzled where does this "logistic function" come from?

The problem is that the deficit of operator may not have a trivial dependence. For example, I chose the logistic function because it must be smooth at the origin and at the holographic screen, and constantly. Surely, you can find a constant, but it is such only in the vicinity of some place. But this approximation is enough, and taken to be null, in the vicinity of earth, and probably to all the universe of which we can see through instruments.

[MTd2]

On a further note. You seem to be much more interested than I am in defending that paper. Given that I am not even being payed for that, I guess I will leave up when doubts are raised occasionally on other threads.