Generalized Galilean Genesis
  The galilean genesis scenario is an alternative to inflation in which the
universe starts expanding from Minkowski in the asymptotic past by violating
the null energy condition stably. Several concrete models of galilean genesis
have been constructed so far within the context of galileon-type scalar-field
theories. We give a generic, unified description of the galilean genesis
scenario in terms of the Horndeski theory, i.e., the most general scalar-tensor
theory with second-order field equations. In doing so we generalize the
previous models to have a new parameter (denoted by {\alpha}) which results in
controlling the evolution of the Hubble rate. The background dynamics is
investigated to show that the generalized galilean genesis solution is an
attractor, similarly to the original model. We also study the nature of
primordial perturbations in the generalized galilean genesis scenario. In all
the models described by our generalized genesis Lagrangian, amplification of
tensor perturbations does not occur as opposed to what happens in quasi-de
Sitter inflation. We show that the spectral index of curvature perturbations is
determined solely from the parameter {\alpha} and does not depend on the other
details of the model. In contrast to the original model, a nearly
scale-invariant spectrum of curvature perturbations is obtained for a specific
choice of {\alpha}.
