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## Main Question or Discussion Point

In his latest paper below, he discusses the microscopic degrees of spacetime and entropy, and how the emergent thermodynamic features of spacetime do not require details of the microscopic degrees of freedom.

Still, I wonder what sort of microscopic degrees of freedom of space time would be compatible with an emergence ? Is time and space on the same footing or distinct? Does it have to be 3+1 or something else?

http://arxiv.org/abs/1003.5665

Surface Density of Spacetime Degrees of Freedom from Equipartition Law in theories of Gravity

T. Padmanabhan

20 pages

(Submitted on 29 Mar 2010)

"I show that the principle of equipartition, applied to area elements of a surface which are in equilibrium at the local Davies-Unruh temperature, allows one to determine the surface number density of the microscopic spacetime degrees of freedom in any diffeomorphism invariant theory of gravity. The entropy associated with these degrees of freedom matches with the Wald entropy for the theory. This result also allows one to attribute an entropy density to the spacetime in a natural manner. The field equations of the theory can then be obtained by extremising this entropy. Moreover, when the microscopic degrees of freedom are in local thermal equilibrium, the spacetime entropy of a bulk region resides on its boundary."

Still, I wonder what sort of microscopic degrees of freedom of space time would be compatible with an emergence ? Is time and space on the same footing or distinct? Does it have to be 3+1 or something else?

http://arxiv.org/abs/1003.5665

Surface Density of Spacetime Degrees of Freedom from Equipartition Law in theories of Gravity

T. Padmanabhan

20 pages

(Submitted on 29 Mar 2010)

"I show that the principle of equipartition, applied to area elements of a surface which are in equilibrium at the local Davies-Unruh temperature, allows one to determine the surface number density of the microscopic spacetime degrees of freedom in any diffeomorphism invariant theory of gravity. The entropy associated with these degrees of freedom matches with the Wald entropy for the theory. This result also allows one to attribute an entropy density to the spacetime in a natural manner. The field equations of the theory can then be obtained by extremising this entropy. Moreover, when the microscopic degrees of freedom are in local thermal equilibrium, the spacetime entropy of a bulk region resides on its boundary."