Subluminal Galilean Genesis

Abstract

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 plus 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.

18 pages, 1 figure

References in corpus (9)

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• Starting the Universe: Stable Violation of the Null Energy Condition and Non-standard Cosmologies
• Galilean Genesis: an alternative to inflation
• Galileon inflation
• Conformal Symmetries of Adiabatic Modes in Cosmology
• Symmetries for Galileons and DBI scalars on curved space
• The quantum mechanics of perfect fluids
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Cited by in corpus (12)

• Beyond the Cosmological Standard Model
• A Critical Review of Classical Bouncing Cosmologies
• Dynamical analysis of generalized Galileon cosmology
• Inflation from Minkowski Space
• Generalized Galilean Genesis
• Consistency Relations for the Conformal Mechanism
• Multiple Soft Limits of Cosmological Correlation Functions
• On the Initial State and Consistency Relations
• Probing the primordial universe with gravitational waves detectors
• Scale-invariant perturbations from NEC violation: A new variant of Galilean Genesis
• A Positive Energy Theorem for P(X,phi) Theories
• Conformal Universe as false vacuum decay