Fat Euclidean gravity with small cosmological constant

Abstract

The cosmological constant problem is usually considered an inevitable feature of any effective theory capturing well-tested gravitational and matter physics, without regard to the details of short-distance gravitational couplings. In this paper, a subtle effective description avoiding the problem is presented in a first quantized language, consistent with experiments and the Equivalence Principle. First quantization allows a minimal domain of validity to be carved out by cutting on the proper length of particle worldlines. This is facilitated by working in (locally) Euclidean spacetime, although considerations of unitarity are still addressed by analytic continuation from Lorentzian spacetime. The new effective description demonstrates that the cosmological constant problem is sensitive to short-distance details of gravity, which can be probed experimentally. "Fat Gravity" toy models are presented, illustrating how gravity might shut off at short but testable distances, in a generally covariant manner that suppresses the cosmological constant. This paper improves on previous work by allowing generalizations to massless matter, non-trivial spins, non-perturbative phenomena, and multiple (metastable) vacua. *

Softened gravity and the extension of the standard model up to infinite energy

“…We do not know of any realistic working examples of softened gravity, but maybe such theories could be built out of some low-scale string theory [36] or fat-gravity [37] models. An attempt to construct a theory of softened gravity was presented in [38].…”

Probing composite gravity in colliders

“…For example, if Λ g is, say, 10 −2 eV, then it could be perfectly consistent for a gravitino with, say, m 3/2 = 10 −3 eV to carry all the (approximately) canonical couplings we expect from supergravity-as long as the gravitino does not receive or mediate a momentum transfer larger than Λ g -even though √ F here would be ∼ TeV which is way above Λ g . To sum up, from the standard effective-field-theoretic view, there seems no prefer- 9 We are assuming that these mesinos are the lightest among the hadrons containing superparticles. 10 Note that this is exactly what is happening in typical weakscale SUSY models in which the visible-sector interactions at the weak scale are taken to be (approximately) supersymmetric, even though the actual SUSY breaking scale is often as high as 10 11 GeV.…”

Rotating Black Holes/Rings at Future Colliders

“…Let us consider two massless particles colliding with impact parameter b and c.m. energy √ s = M i so that each particle has momentum c Recently, the opposite possibility is proposed that the gravity becomes weak rather than strong above its cut-off scale set at ∼ 10 −3 eV, though it is yet unknown how to realize it in some quantum gravity model (or in string theory) [7]. d Originally the argument of the correspondence principle is for fixed energy (mass), varying the string coupling [9], but the same argument holds for fixed coupling varying the energy (mass).…”