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A Gravitational Entropy Proposal
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A Gravitational Entropy Proposal
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We propose a thermodynamically motivated measure of gravitational entropy based on the Bel-Robinson tensor, which has a natural interpretation as the effective super-energy-momentum tensor of free gravitational fields. The specific form of this measure differs depending on whether the gravitational field is Coulomb-like or wave-like, and reduces to the Bekenstein-Hawking value when integrated over the interior of a Schwarzschild black hole. For scalar perturbations of a Robertson-Walker geometry we find that the entropy goes like the Hubble weighted anisotropy of the gravitational field, and therefore increases as structure formation occurs. This is in keeping with our expectations for the behaviour of gravitational entropy in cosmology, and provides a thermodynamically motivated arrow of time for cosmological solutions of Einstein's field equations. It is also in keeping with Penrose's Weyl curvature hypothesis.
Forward citations
Cited by 4 Pith papers
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Eckart heat-flux applicability in $F(\Phi,X)R$ theories and the existence of temperature gradients
Eckart heat flux holds for all timelike scalar configurations in F(Φ,X)R + G theories if and only if F_X ≡ 0, reducing the theory to a Jordan-like subclass of Horndeski.
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Landauer entropy of spacetime
A geometrical entropy for static spherically symmetric spacetimes is defined from Landauer's principle applied to geodesic congruences, obeys a second law, and equals Bekenstein-Hawking entropy.
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Landauer entropy of spacetime
Defines Landauer entropy for static spherically symmetric spacetimes as a surface integral over geodesic entropies, establishes a second law under mild assumptions, and relates the result to Bekenstein-Hawking entropy.
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Multidimensional arrow of time
The direction of time is claimed to be fixed by the exponentially growing entropy of expanding extra dimensions, which dominates every other entropy source in the universe.
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