Bi-galileon theory I: motivation and formulation

By Antonio Padilla, P. Saffin, Shuang-Yong Zhou. 2010

137 citations recorded by the source corpus.

We introduce bi-galileon theory, the generalisation of the single galileon model introduced by Nicolis et al. The theory contains two coupled scalar fields and is described by a Lagrangian that is invariant under Galilean shifts in those fields. This paper is the first of two, and focuses on the motivation and formulation of the theory. We show that the boundary effective theory of the cascading cosmology model corresponds to a bi-galileon theory in the decoupling limit, and argue that this is to be expected for co-dimension 2 braneworld models exhibiting infra-red modification of gravity. We then generalise this, by constructing the most general bi-galileon Lagrangian. By coupling one of the galileons to the energy-momentum tensor, we pitch this as a modified gravity theory in which the modifications to General Relativity are encoded in the dynamics of the two galileons. We initiate a study of phenomenology by looking at maximally symmetric vacua and their stability, developing elegant geometric techniques that trivially explain why some of the vacua have to be unstable in certain cases (eg DGP). A detailed study of phenomenology appears in our companion paper.

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

View Paper: https://www.semanticscholar.org/paper/56d6523507780b456553fdebf5a438c9f3912878

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Citations in the corpus

Horndeski theory and beyond: a review (2019, unknown): “ralize the Galileon/Horndeski theory to multiple scalar ﬁelds. The Galileon is generalized to mixed combinations of p-form ﬁelds in [54], a special case of which is the bi- and multi- Galileon theory [55, 56]. The multi-Galileon theory can also be derived from a probe brane embedded in a higher-dime”
Zoology of condensed matter: framids, ordinary stuff, extra-ordinary stuff (2015, background): “J H E P 0 6 ( 2 0 1 5 ) 1 5 5 These symmetries define a multi-galileon theory [62, 63], with a multiplet of scalars φab(x) transforming as a spin-2 representation of the internal SO(3) symmetry, and as”
On couplings to matter in massive (bi-)gravity (2014, background): “The couplings between the two fields χ and π are nothing else but a specific case of a generalised bi-Galileon [102, 103] and are thus free of Ostrogadski instability [97, 104].”
Modified Gravity and Cosmology (2011, background): “Indeed, for √ −∂2 1/rc, the interaction term goes like [839, 1017] Γint = − 1 3 √ 6Λ3 ∫ d(4)x(∂π̂)(2)∂(2)π̂ + sub-leading interactions, (770)”
Dark Energy (2024, unknown): “Then, there are the galileon theory [62] and the multi-galileon theory [63, 64] that are similar to the scalar-tensor theories.”
The imperfect fluid behind kinetic gravity braiding (2011, background): “Nonetheless, these theories have been named galileon theories and a significant body of work has already been carried out analysing their impact not only on cosmological solutions [28–45], but also in other circumstances [46–55].”
Interacting spin-2 fields (2012, background): “Multi-metric theories should yield some kind of multi-galileon along the lines of [37, 38, 39] (though many of these multi-galileon theories also have instabilities or superluminality [40, 41, 42, 43]).”