Reconstruction method in the kinetic gravity braiding theory with shift-symmetric
Department of General Relativity and Gravitation, Institute of Physics, Kazan Federal University, Kremlevskaya str. 18, 420008, Kazan, Russia
2 Department of Higher Mathematics, Kazan State Power Engineering University, Krasnoselskaya str. 51, 420066, Kazan, Russia
Accepted: 25 May 2021
Published online: 28 May 2021
We present a reconstruction method for flat Friedman–Robertson–Walker (FRW) spacetime in a subclass of Horndeski theory—specifically shiftsymmetric, the kinetic gravity braiding (KGB) theory with a non-vanishing conserved current. Choosing the form of the Hubble parameter and kinetic density X, we restore the functions , of the KGB model. In order to determine whether the model is free of ghosts and Laplacian instabilities and thus cosmologically viable, two conditions related to scalar perturbations are checked. Initially, the Lagrangian does not include the term that describes, for example, the perfect fluid with the EoS parameter . This fluid can provide a dynamic solution H(t), X(t). In the presented method, dynamic solutions are provided by a nonzero scalar charge associated with the shift symmetry . Reconstruction examples are given for models: an perfect fluid, a unified description dark energy–dark matter, a post-inflationary transition to the radiation-dominated phase.
© The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature 2021