Reviving non-minimal Horndeski-like theories after GW170817: kinetic coupling corrected Einstein–Gauss–Bonnet inflation

DOI10.1088/1361-6382/ABCE47zbMATH Open1479.83297arXiv2006.05512OpenAlexW3110337391MaRDI QIDQ5162506

Author name not available (Why is that?)

Publication date: 2 November 2021

Published in: (Search for Journal in Brave)

Abstract: After the recent GW170817 event of the two neutron stars merging, many string corrected cosmological theories confronted the non-viability peril. This was due to the fact that most of these theories produce massive gravitons primordially. Among these theories were the ones containing a non-minimal kinetic coupling correction term in the Lagrangian, which belong to a subclass of Horndeski theories. In this work we demonstrate how these theories may be revived and we show how these theories can produce primordial gravitational waves with speed

c_{T}^{2} = 1

in natural units, thus complying with the GW170817 event. As we show, if the gravitational action of an Einstein-Gauss-Bonnet theory also contains a kinetic coupling of the form

s i m x i (p h i) G^{m u u} p a r t i a l_{m} u p h i p a r t i a l_{u} p h i

, the condition of having primordial massless gravitons, or equivalently primordial gravitational waves with speed

c_{T}^{2} = 1

in natural units, results to certain conditions on the scalar field dependent coupling function of the Gauss-Bonnet term, which is also the non-minimal coupling of the kinetic coupling. We extensively study the phenomenological implications of such a theory focusing on the inflationary era, by only assuming slow-roll dynamics for the scalar field. Accordingly, we briefly study the case that the scalar field evolves in a constant-roll way. By using some illustrative examples, we demonstrate that the viability of the theoretical framework at hand may easily be achieved. Also, theories containing terms of the form

s i m x i (p h i) B o x p h i g^{m u u} p a r t i a l_{m} u p h i p a r t i a l_{u} p h i

and

s i m x i (p h i) l e f t (g^{m u u} p a r t i a l_{m} u p h i p a r t i a l_{u} p h i i g h t)^{2}

also lead to the same gravitational wave speed as the theory we shall study in this paper, so this covers a larger class of Horndeski theories.

Full work available at URL: https://arxiv.org/abs/2006.05512

zbMATH Keywords

No records found.

Mathematics Subject Classification ID

No records found.

This page was built for publication: Reviving non-minimal Horndeski-like theories after GW170817: kinetic coupling corrected Einstein–Gauss–Bonnet inflation

Report a bug (only for logged in users!)Click here to report a bug for this page (MaRDI item Q5162506)