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Article overview
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Serendipitous discoveries in nonlocal ghost-free gravity theory: dark energy and dark matter | | Andrei O.Barvinsky
; | | Date: |
19 Dec 2011 | | Abstract: | We present a class of generally covariant nonlocal gravity models briefly
reported in arXiv:1107.1463, which have a flat-space general relativistic (GR)
limit and also possess a stable de Sitter (dS) or Anti-de Sitter (AdS)
background with an arbitrary value of its cosmological constant. The nonlocal
action of the theory is formulated in the Euclidean signature spacetime and is
understood as an approximation to the quantum effective action (generating
functional of one-particle irreducible diagrams) originating from fundamental
quantum gravity theory. Using the known relation between the Schwinger-Keldysh
technique for quantum expectation values and the Euclidean quantum field theory
we derive from this action the {em causal} effective equations of motion for
mean value of the metric field in the physical Lorentzian-signature spacetime.
Thus we show that the (A)dS background of the theory carries as free
propagating modes massless gravitons having two polarizations identical to
those of the Einstein theory with a cosmological term. The on-shell action of
the theory is vanishing both for the flat-space and (A)dS backgrounds which
play the role of stable vacua underlying respectively the ultraviolet and
infrared phases of the theory. We also obtain linearized gravitational
potentials of compact matter sources and show that in the infrared (A)dS phase
their effective gravitational coupling $G_{
m eff}$ can be essentially
different from the Newton gravitational constant $G_N$ of the short-distance GR
phase. When $G_{
m eff}gg G_N$ the (A)dS phase can be regarded as a strongly
coupled infrared modification of Einstein theory not only describing the dark
energy mechanism of cosmic acceleration but also simulating the dark matter
phenomenon by enhanced gravitational attraction at long distances. | | Source: | arXiv, 1112.4340 | | Services: | Forum | Review | PDF | Favorites | |
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