Erik Verlinde video on entropic force gravity

[marcus]

http://pirsa.org/10050022/
The Emergence of Gravity
Erik Verlinde
12/05/2010
"Theoretical insights originated from the study of black holes combined with developments in string theory indicate that space time and gravity are emergent. A central role in these developments is played by the holographic principle. I will present a heuristic argument that indicates that at a microscopic level gravity is an entropic force caused by changes in the available phase space ..."

We've looked at several papers about this, by Verlinde himself, Lee Smolin, Jerzy Kowalski-Glickman, Andy Randono, George Smoot, and others. But sometimes watching a video can provide additional intuition, so people might want to check this out.

 

[WhoWee]

Thanks marcus - I forwarded this link to a few friends also.

 

[humanino]

It was indeed very interesting. Although I am rather skeptical about his scheme, I must admit he addresses the question with lucidity. Thank you for the link Marcus.

 

[Fra]

Thanks for the link, I just watched it as well.

My opinon didn't change from the video though, I still think the general new perspective his thinking represents is good and interesting, but I also think that the final qualifiers for this "scheme" depends on wether the still open issues with the scheme itself is resolved. I think it can be done, this is why I like his research.

The big remaining issues as I see it is

1) to explain the orign of the holographic principle, in a more general way (as somehow communication channels tied to observers etc)

2) the put the "entropic reasoning" in the context where the CHOICE OF observer is handled. Verlinde says himself that there is always an implicit choice of an observer. But this itself surely feeds further and deeper questions - also related to his assumption of the existence of microscopic time, since this is in his view tide to the choice of observer. Which is somehow implicit in his entire logic.

I can understand why some people don't like this scheme, and myself don't find the scheme complete either, there are remaining points that needs to be sorted out. The difference is though that I think it can be done, so I think it's good and the new unanswered questions these steps does generate are better than the old questions.

/Fredrik

 

[sbrothy]

"Comment on "On the Origin of Gravity and the Laws of Newton" by Erik P. Verlinde"
-- http://arxiv.org/abs/1002.2668

"We show that Verlinde's idea of gravity as an entropic force is untenable. The main reason is that Verlinde made a mistake in identifying the causal relationship between physical variables when applying the first law of thermodynamics to the interacting process between a holographic screen and a particle. Moreover, it is shown that Verlinde's argument also has some other flaws."

This looks pretty devastating to Verlinde's idea. "Deadly flaw [...]". Even if it holds true it doesn't entirely kill the idea of gravity being emergent or entropic does it? As a layman it's sometimes extremely hard to follow what's going on in the ivory tower. :)

Btw, if other non-scientists are lurking they may benefit from this quick intro to the entropic argument. I found it quite helpful.:

"It From Bit - Entropic Gravity For Pedestrians"
-- http://www.scientificblogging.com/hammock_physicist/it_bit_entropic_gravity_pedestrians

 

[marcus]

Sbrothy,
about the paper you found and brought up for us to discuss, "Comments on..."...

The author Sheldon Gao is a graduate student at the University of Sydney, but not apparently in physics---he says he is at a school of "philosophical and historical investigations" and also a group in the philosophy department called "center for time" which looks into the metaphysics of time.

I could not find that Sheldon Gao has ever published any peer review research in physics. Maybe you will have better luck looking.

I think he also uses the name Shan Gao. Sheldon may be an anglicized version of Shan.
So if you want to get a sense of his track record you might look under both names, for papers etc.

As a layman it's sometimes extremely hard to follow what's going on in the ivory tower.

Then probably the safest thing to do, as a layman, if you want to avoid wasting time barking up the wrong trees, is simply to ignore anything new on Arxiv where the author does not already have a strong established publication track record.

You can usually rely on knowledgeable physicists being more often right in their reaction to something new by a relatively unknown researcher. If there is something worth checking out from Sheldon Gao, we will hear about it before long.

 

[Fra]

first comment:

I'll try to read that paper later, but my first impression just skimming it is that "deathly flaw" is overreacting and maybe even missing the point?

As I see it first of all, Verlinde has not "deduced" anything. He has presented heuristic arguments that the logic of the connection between gravity and statistics is reversed.

I like the general direction, but I also have objections to Verlindes reasoning, but I can't imagine calling it deadly flawed. That just sounds akward.

Also I find the critique about the scrambled direction of causality to almost be missing what I personally think is the beauty here. As I've argued before, my personal opinon on the "entropic reasoning" is that from coherence of reasoning, it only makes sense in connection to an evolutionary model, and let us ask what is the cause and effect in evolution?

Clearly there are several "mechanisms", there is variation/mutation and there is selection. The old style causal chain logic does not quite apply since random variation has no distinguishable cause at all (think dx) and the selection is simply probabilistic/entropic.

So the overall process is "caused" by both random/undecidable elements and selection by fitness which is essentially also entropic.

IMHO, I think the better light in which to see this entropic arguments is where the framework of old realist type of causal chains doesn't quite play the same role.

I think that causality itself must be emergent. IMO at least the notion of timeless fundamantela causal laws, are replaced by a new form of emergent and evolving constraints, but this is also part of my critique to Verlinde, but I think that's topis for future development, you have to start somewhere, and verlinde does.

In that sense, I have a feeling that the critique against scrambled causality is missing the beauty of the evolving concept, but I'll try to read it properly later and see if I missed anything deeper. Maybe I judged prematurely.

/Fredrik