What is the Entropy in Entropic Gravity?

Jan 27, 2016
13 pages
Published in:
  • Phys.Rev.D 93 (2016) 12, 124052
  • Published: Jun 21, 2016
e-Print:
Report number:
  • CALT-TH-2015-038

Citations per year

2016201820202022202402468
Abstract: (APS)
We investigate theories in which gravity arises as a consequence of entropy. We distinguish between two approaches to this idea: holographic gravity, in which Einstein’s equation arises from keeping entropy stationary in equilibrium under variations of the geometry and quantum state of a small region, and thermodynamic gravity, in which Einstein’s equation emerges as a local equation of state from constraints on the area of a dynamical light sheet in a fixed spacetime background. Examining holographic gravity, we argue that its underlying assumptions can be justified in part using recent results on the form of the modular energy in quantum field theory. For thermodynamic gravity, on the other hand, we find that it is difficult to formulate a self-consistent definition of the entropy, which represents an obstacle for this approach. This investigation points the way forward in understanding the connections between gravity and entanglement.
Note:
  • 25 pages, 4 figures
  • gravitation: holography
  • force: entropy
  • space-time: background
  • Einstein equation
  • thermodynamical
  • field theory
  • equation of state
  • entanglement
  • geometry
  • modular