Galilean Genesis: An Alternative to inflation

By P. Creminelli, Alberto Nicolis, E. Trincherini. 2010

341 citations recorded by the source corpus.

We propose a novel cosmological scenario, in which standard inflation is replaced by an expanding phase with a drastic violation of the Null Energy Condition (NEC): >> H2. The model is based on the recently introduced Galileon theories, which allow NEC violating solutions without instabilities. The unperturbed solution describes a Universe that is asymptotically Minkowski in the past, expands with increasing energy density until it exits the regime of validity of the effective field theory and reheats. This solution is a dynamical attractor and the Universe is driven to it, even if it is initially contracting. The study of perturbations of the Galileon field reveals some subtleties, related to the gross violation of the NEC and it shows that adiabatic perturbations are cosmologically irrelevant. The model, however, suggests a new way to produce a scale invariant spectrum of isocurvature perturbations, which can later be converted to adiabatic: the Galileon is forced by symmetry to couple to the other fields as a dilaton; the effective metric it yields on the NEC violating solution is that of de Sitter space, so that all light scalars will automatically acquire a nearly scale-invariant spectrum of perturbations.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/a8c5c64502a06c163953d59c46fc15ceac6498b3

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Citations in the corpus

An infinite set of Ward identities for adiabatic modes in cosmology (2013, background): “The conformal mechanism [82–88], in particular, relies the spontaneous breaking of conformal invariance on approximate flat space, with symmetry breaking pattern SO(4, 2) → SO(4, 1).”
A systematic approach to generalisations of General Relativity and their cosmological implications (2018, background): “The direct cosmological application of covariant Galileons witnessed a flurry of investigations concerning self-accelerating de Sitter solutions [223, 224], inflation [225, 226, 227, 228], dark energy and its observational implications [229, 222, 230, 231, 232, 51, 52].”
Conformal consistency relations for single-field inflation (2012, background): “Similarly one should be able to extend these relations to models where the SO(4, 1) symmetry is not the isometry group of de Sitter, but a subgroup of the 4d conformal group SO(4, 2), with additional constraints induced by the non-linear realization of SO(4, 2) [30, 2, 31, 32].”
Imperfect Dark Energy from Kinetic Gravity Braiding (2010, background): “See also Refs.”
Modified Gravity and Cosmology (2011, neutral): “condition without introducing any instability [964, 343].”
Horndeski theory and beyond: a review (2019, methodology): “A novel NEC-violating cosmological scenario called the galilean genesis was proposed based on the cubic Galileon theory [103].”
Generalized Galileons: instabilities of bouncing and Genesis cosmologies and modified Genesis (2016, methodology): “Indeed, in the original Genesis model [14] as well as in its variants [15–22], the initial super-accelerating stage can occur without ghosts and gradient instabilities (although there is still an issue of superluminality [23, 24]).”
Massive Gravity (2014, background): “[112, 110, 311, 312, 218, 219] for related discussions on super- versus sub- luminal propagation in conformal Galileon and other DBI-related models.”
G-bounce (2011, methodology): “We will discuss such models in this section and specialise to the discussion of the so-called conformal Galileon model [68, 76, 77].”
On soft limits of inflationary correlation functions (2012, background): “This explains the scale-invariance of the two-point function [53].”