The imperfect fluid behind kinetic gravity braiding

By O. Pujolàs, I. Sawicki, A. Vikman. 2011

190 citations recorded by the source corpus.

A bstractWe present a standard hydrodynamical description for non-canonical scalar field theories with kinetic gravity braiding. In particular, this picture applies to the simplest galileons and k-essence. The fluid variables not only have a clear physical meaning but also drastically simplify the analysis of the system. The fluid carries charges corresponding to shifts in field space. This shift-charge current contains a spatial part responsible for diffusion of the charges. Moreover, in the incompressible limit, the equation of motion becomes the standard diffusion equation. The fluid is indeed imperfect because the energy flows neither along the field gradient nor along the shift current. The fluid has zero vorticity and is not dissipative: there is no entropy production, the energy-momentum is exactly conserved, the temperature vanishes and there is no shear viscosity. Still, in an expansion around a perfect fluid one can identify terms which correct the pressure in the manner of bulk viscosity. We close by formulating the non-trivial conditions for the thermodynamic equilibrium of this imperfect fluid.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/0dd9e1ef243251cc68605ed214a6dcf95e296ff2

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Citations in the corpus

A unifying description of dark energy (2014, background): “This phenomenon has been called kinetic braiding in [36, 37].”
Maximal freedom at minimum cost: linear large-scale structure in general modifications of gravity (2014, background): “• Braiding αB represents a space-like energy flux vector qi in this frame (a T 0i contribution); essentially this is a generalisation of the imperfect contributions described for kinetic gravity braiding models in [49].”
G-bounce (2011, background): “We present the results in the form of [73] and [75].”
hi_class: Horndeski in the Cosmic Linear Anisotropy Solving System (2016, background): “2 This general class of actions includes the vast majority of universally coupled models of dark energy with one scalar degree of freedom: quintessence [18, 19], Brans-Dicke models [20], k-essence [21, 22], kinetic gravity braiding [23–25], covariant galileons [15, 26], disformal and Dirac-Born-Infe”
Exploring gravitational theories beyond Horndeski (2014, background): “In particular, M(2), αK , αB and αT respectively parameterize the effective Planck mass, a modification of the scalar kinetic term [34, 35], a kinetic mixing between the scalar and the metric (the so-called braiding) [36, 37, 38, 39] and a tensor speed excess.”
Horndeski theory and beyond: a review (2019, background): “ation of the metric, ˜gµν = C(φ)gµν. However, once G3(φ,X) is introduced, the mixing becomes essential and cannot be removed by such a ﬁeld redeﬁnition. This nature is called kinetic gravity braiding [28, 67]. Equations (32), (33), and (34) are useful for studying the background dynamics of inﬂation”
Galileon gravity in light of ISW, CMB, BAO and H0 data (2017, methodology): “At the level of perturbations the non-linear nature of the said kinetic interactions effectively couples the derivatives of the Galileon and metric fields together (in a process commonly dubbed as “kinetic gravity braiding” [9, 10]).”