Exploring the Nature of Gravity

Abstract

I clarify the differences between various approaches in the literature which attempt to link gravity and thermodynamics. I then describe a new perspective based on the following features: (1) As in the case of any other matter field, the gravitational field equations should also remain unchanged if a constant is added to the Lagrangian; in other words, the field equations of gravity should remain invariant under the transformation $T_b^a\to T_b^a+{\delta }_b^a$(constant). (2) Each event of spacetime has a certain number ($f$) of microscopic degrees of freedom (`atoms of spacetime'). This quantity $f$ is proportional to the area measure of an equi-geodesic surface, centered at that event, when the geodesic distance tends to zero. The spacetime should have a zero-point length in order for $f$ to remain finite. (3) The dynamics is determined by extremizing the heat density at all events of the spacetime. The heat density is the sum of a part contributed by matter and a part contributed by the atoms of spacetime, with the latter being $L_P^{-4}f$. The implications of this approach are discussed.

Elaborates on the results presented in five recent talks: Keynote address in (i) EmQM15, Vienna, 23-25 Oct, 2015; Plenary talks in (ii) 35th Max Born Symposium - The Planck Scale II, Wroclaw, 7-12 Sept, 2015 and (iii) ICGC-2015, Mohali, 14-16 Dec 2015; Colloquia at (iv) IAP, Paris, 30 Oct 2015 and (v) TIFR, Mumbai, 5 Oct 2015; two figures, 26 pages

References in corpus (11)

• Entropy of Null Surfaces and Dynamics of Spacetime
• Emergent Gravity Paradigm: Recent Progress
• Entropy density of spacetime and the Navier-Stokes fluid dynamics of null surfaces
• Evolution of Spacetime arises due to the departure from Holographic Equipartition in all Lanczos-Lovelock Theories of Gravity
• What is the Entropy in Entropic Gravity?
• Grin of the Cheshire cat: Entropy density of spacetime as a relic from quantum gravity
• Vacuum Fluctuations and the Small Scale Structure of Spacetime
• Geometrical variables with direct thermodynamic significance in Lanczos-Lovelock gravity
• The thermodynamic structure of Einstein tensor
• Finite entanglement entropy from the zero-point-area of spacetime
• The thermodynamics of quantum spacetime histories

Cited by in corpus (10)

• The Atoms Of Space, Gravity and the Cosmological Constant
• Do We Really Understand the Cosmos?
• Entropy Maximization in the Emergent Gravity Paradigm
• The atoms of spacetime and the cosmological constant
• Emergent Gravity in a Holographic Universe
• Spacetime atoms and extrinsic curvature of equi-geodesic surfaces
• Zero-point gravitational field equations
• Emergent gravity from off-shell energy fixing
• Emergent Gravity from an Augmented Variational Principle
• Necessity of Quantizable Geometry for Quantum Gravity