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Copernicus
2018-Aug-11, 05:44 AM
I found this article on emergent gravity. https://phys.org/news/2018-08-flaw-emergent-gravity.html apparently spherical symmetric surfaces obey the first law of thermodynamics, but other surfaces do not. Does this rule out string theory?

Shaula
2018-Aug-11, 06:19 AM
Not really, because the assumption that they do is not baked into the theory in the way that it is for emergent gravity. In the basic form of emergent gravity you use the equipartition theorem to link temperature and energy to an information like variable (degrees of freedom, linked to the Planck area) - this is part of the chain of logic used to derive Newton's laws under emergent gravity. A key part of that is that they system is in thermodynamic equilibrium, which is tough to get to if your system doesn't behave in accordance with the underlying rules of thermodynamics.

Copernicus
2018-Aug-11, 12:50 PM
Not really, because the assumption that they do is not baked into the theory in the way that it is for emergent gravity. In the basic form of emergent gravity you use the equipartition theorem to link temperature and energy to an information like variable (degrees of freedom, linked to the Planck area) - this is part of the chain of logic used to derive Newton's laws under emergent gravity. A key part of that is that they system is in thermodynamic equilibrium, which is tough to get to if your system doesn't behave in accordance with the underlying rules of thermodynamics.

I thought Eric Verlinde's Theory was an emergent gravity theory that included string theory.

Shaula
2018-Aug-11, 01:17 PM
I thought Eric Verlinde's Theory was an emergent gravity theory that included string theory.
Yes, but string theory does not include Verlinde's theory or any of the emergent gravity theories. They are extensions to it. Extensions which, in this case, may not be viable (not convinced the proof is watertight yet - there may be a way to restore or remove the need for the thermodynamic component). So because the particular issue that has been raised is actually not required for the core string theory component to be viable it is not affected by what they have said.

Copernicus
2018-Aug-14, 02:41 AM
Yes, but string theory does not include Verlinde's theory or any of the emergent gravity theories. They are extensions to it. Extensions which, in this case, may not be viable (not convinced the proof is watertight yet - there may be a way to restore or remove the need for the thermodynamic component). So because the particular issue that has been raised is actually not required for the core string theory component to be viable it is not affected by what they have said.

Thanks Shuala