Primordial non-Gaussianity from the DBI Galileons
  We study primordial fluctuations generated during inflation in a class of
models motivated by the DBI Galileons, which are extensions of the DBI action
that yield second order field equations. This class of models generalises the
DBI Galileons in a similar way with K-inflation. We calculate the primordial
non-Gaussianity from the bispectrum of the curvature perturbations at leading
order in the slow-varying approximations. We show that the estimator for the
equilateral-type non-Gaussianity, $f_{\rm NL} ^{equil}$, can be applied to
measure the amplitude of the primordial bispectrum even in the presence of the
Galileon-like term although it gives a slightly different momentum dependence
from K-inflation models. For the DBI Galileons, we find $-0.32 /c_s^2 < f_{\rm
NL} ^{equil} < -0.16/c_s^2$ and large primordial non-Gaussianities can be
obtained when $c_s$ is much smaller than 1 as in the usual DBI inflation. In
G-inflation models, where a de Sitter solution is obtained without any
potentials, the non-linear parameter is given by $f_{\rm NL}^{equil} = 4.62
r^{-2/3}$ where $r$ is the tensor to scalar ratio, giving a stringent
constraint on the model.
