CosmoCoffee

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

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)?

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