Generalized Galileons: instabilities of bouncing and Genesis cosmologies and modified Genesis

By M. Libanov, S. Mironov, V. Rubakov. 2016

161 citations recorded by the source corpus.

We study spatially flat bouncing cosmologies and models with the early-time Genesis epoch in a popular class of generalized Galileon theories. We ask whether there exist solutions of these types which are free of gradient and ghost instabilities. We find that irrespectively of the forms of the Lagrangian functions, the bouncing models either are plagued with these instabilities or have singularities. The same result holds for the original Genesis model and its variants in which the scale factor tends to a constant as t → −∞. The result remains valid in theories with additional matter that obeys the Null Energy Condition and interacts with the Galileon only gravitationally. We propose a modified Genesis model which evades our no-go argument and give an explicit example of healthy cosmology that connects the modified Genesis epoch with kination (the epoch still driven by the Galileon field, which is a conventional massless scalar field at that stage).

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics, Statistical and Nonlinear Physics

View Paper: https://www.semanticscholar.org/paper/6ed229999485479f8b964a3ad4e815e219b11c4e

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Citations in the corpus

Horndeski theory and beyond: a review (2019, background): “In fact, it can be proven that the appearance of gradient instabilities is generic to all nonsingular cosmological solutions in the Horndeski theory [126, 127] (see also [128, 129]).”
The Effective Field Theory of nonsingular cosmology (2016, methodology): “Recently, Libanov, Mironov and Rubakov (LMR) have proved a no-go theorem, which shows that healthy nonsingular cosmological models based on the cubic Galileon does not exist [33].”
Generic instabilities of nonsingular cosmologies in Horndeski theory: A no-go theorem (2016, unknown): “[34] that bouncing and genesis models suffer from instabilities or have singularities for the scalartensor theory whose Lagrangian is of the form”