Generic instabilities of nonsingular cosmologies in Horndeski theory: A no-go theorem

By Tsutomu Kobayashi. 2016

144 citations recorded by the source corpus.

The null energy condition can be violated stably in generalized Galileon theories, which gives rise to the possibilities of healthy nonsingular cosmologies. However, it has been reported that in many cases cosmological solutions are plagued with instabilities or have some pathologies somewhere in the whole history of the universe. Recently, this was shown to be generically true in a certain subclass of the Horndeski theory. In this short paper, we extend this no-go argument to the full Horndeski theory and show that nonsingular models (with flat spatial sections) in general suffer from either gradient instabilities or some kind of pathology in the tensor sector. This implies that one must go beyond the Horndeski theory to implement healthy nonsingular cosmologies.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/68bbfcac44ce734d3165f23830cd668bc954d674

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Citations in the corpus

The Effective Field Theory of nonsingular cosmology (2016, methodology): “10) will produce the key inequality in Kobayashi’s paper [35].”
Horndeski theory and beyond: a review (2019, background): “directly to the violation of the energy condition. 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]). As we have seen, one can construct a NEC-violating solution that i”