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Journal of High Energy Physics 09 (2012) 009
Lorentz-violating vs. ghost gravitons: the example of Weyl gravity
N. Deruelle1, M. Sasaki2, Y. Sendouda1, A. Youssef
(2012-09)

We show that the ghost degrees of freedom of Einstein gravity with a Weyl term can be tamed by a simple mechanism that invokes local Lorentz symmetry breaking. We demonstrate how the mechanism works in a cosmological setting. The presence of the Weyl term forces a redefinition of the quantum vacuum state of the tensor perturbations. As a consequence the amplitude of their spectrum blows up when the Lorentz-violating scale becomes comparable to the Hubble radius. Such a behaviour is in sharp contrast to what happens in standard Weyl gravity where the gravitational ghosts smoothly damp out the spectrum of primordial gravitational waves.
1:  APC - UMR 7164 - AstroParticule et Cosmologie
2:  Yukawa Institute for Theoretical Physics
APC - THEORIE
Physics/General Relativity and Quantum Cosmology

Physics/High Energy Physics - Theory
Cosmology of Theories beyond the SM – Models of Quantum Gravity – Classical Theories of Gravity
Fulltext link: 
http://fr.arXiv.org/abs/1202.3131