Journal
JOURNAL OF HIGH ENERGY PHYSICS
Volume -, Issue 2, Pages -Publisher
SPRINGER
DOI: 10.1007/JHEP02(2013)006
Keywords
Classical Theories of Gravity; Conformal and W Symmetry; Space-Time Symmetries
Categories
Funding
- NASA ATP [09-ATP09-0049, NNX11AI95G]
- DOE [DE-FG02-92-ER40699]
- University of Pennsylvania
- Government of Canada through Industry Canada
- Province of Ontario through the Ministry of Research and Innovation
- Alfred P. Sloan Foundation
- NSF [PHY-1145525]
- EU [PITN-GA-2009-237920]
- Division Of Physics
- Direct For Mathematical & Physical Scien [1001296] Funding Source: National Science Foundation
- Division Of Physics
- Direct For Mathematical & Physical Scien [1145525] Funding Source: National Science Foundation
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We put forward an improved version of the Galilean Genesis model that addresses the problem of superluminality. We demote the full conformal group to Poincare symmetry and dilations, supplemented with approximate galilean shift invariance in the UV and at small field values. In this way fluctuations around the NEC-violating cosmological background are made substantially subluminal, and superluminality cannot be reached by any small change of the solution, in contrast with the original model. Dilation invariance still protects the scale-invariance of correlation functions of a massless test scalar - which is the source of the observed cosmological fluctuations - but the explicit breaking of the conformal group can be potentially observed in higher-order correlators. We also highlight a subtlety in matching the NEC-violating phase with the standard cosmological evolution, and discuss the possible couplings of the Galileon to gravity.
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