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[1001.0785] On the Origin of Gravity and the Laws of Newton
 
Authors:Erik P. Verlinde
Abstract:Starting from first principles and general assumptions Newton's law of gravitation is shown to arise naturally and unavoidably in a theory in which space is emergent through a holographic scenario. Gravity is explained as an entropic force caused by changes in the information associated with the positions of material bodies. A relativistic generalization of the presented arguments directly leads to the Einstein equations. When space is emergent even Newton's law of inertia needs to be explained. The equivalence principle leads us to conclude that it is actually this law of inertia whose origin is entropic.
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Shaun Thomas



Joined: 26 Oct 2006
Posts: 3
Affiliation: University College London (UCL)

PostPosted: March 24 2010  Reply with quote

This paper by Erik Verlinde discusses the idea of gravity as an 'emergent' macroscopic phenomenon rather than gravity as a fundamental force. The reasoning behind this is related to holography (information on screens) and [changes in] entropy - which is commonplace in black hole physics (E.g. Hawking and Bekenstein).

Despite the earlier link about the Easson, Frampton and Smoot paper I thought it would be interesting to discuss this idea as an actual concept/theory. Please have a read and post your opinions, thoughts, questions and answers - I'm keen to hear them.

shaun
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Alexander B Fry



Joined: 24 Sep 2008
Posts: 1
Affiliation: University of Washington

PostPosted: March 30 2010  Reply with quote

First, some clarifying comments on the paper by Hossenfelder http://arxiv.org/abs/1003.1015

I have more questions than answers. My understanding is that [gravitational] forces are the result of entropy differences. However, on the smallest of scales the number of possible microstates, and thus entropy, is not dependent on the position of elementary particles. How would gravity work through entropy here?

Verlinde has also said that it is a decade old result that assuming the first law of thermodynamics, the holographic principle, and the identification of temperature with the Unruh temperature, that one can derive the Einstein equations. If this is so, does that make gravity a non-fundamental force in the holographic framework (or for that matter any framework where the bulk degrees of freedom allow for a holographic description)?
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Shaun Thomas



Joined: 26 Oct 2006
Posts: 3
Affiliation: University College London (UCL)

PostPosted: March 30 2010  Reply with quote

It seems that http://arxiv.org/abs/1003.1015 reverses the argument from [thermodynamic/entropic => Newtonian formulation] to [Newtonian formation => thermodynamic entropic], that is, both are equivalent.

With regards to your question my (limited) understanding would be: given that gravity is seen as emergent it is not fundamental. In this way, on 'small scales' there is no gravitational force. I figure that this is fairly consistent with (no) observations in that domain.

I wonder (if being speculative) whether one could examine scenarios where the force on objects is low. Does this mean the change in states is small (and therefore subject to fluctuations)? The paper above seems to shy away from talking about 'bits' on a screen. However, if these were quantised in some way perhaps there is some low gravity prediction in this model whereby force/acceleration also become discrete? (Not wishing to fuel more MOND-like theories - just discussion :) )

shaun
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