Late-time Cosmology of scalar field assisted $f(\mathcal{G})$ gravity
  In this work we present the late-time behaviour of the Universe in the
context of Einstein-Gauss-Bonnet gravitational theory. The theory involves a
scalar field, which represents low-effective quantum corrections, assisted by a
function $f(\mathcal{G})$ solely depending from the Gauss-Bonnet topological
invariant $\mathcal{G}$. It is considered that the dark energy serves as the
impact of all geometric terms, which are included in the gravitational action
and the density of dark energy acts as a time dependent cosmological constant
evolving with an infinitesimal rate and driving the Universe into an
accelerating expansion. We examine two cosmological models of interest. The
first involves a canonical scalar field in the presence of a scalar potential
while the second, involves a scalar field which belongs to a generalized class
of theories $f(\phi,X)$ namely the k-essence scalar field in the absence of
scalar potential. As it is proved, the aforementioned models are in consistency
with the latest Planck data and in relatively good agreement with the
$\Lambda$CDM standard cosmological model. The absence of dark energy
oscillations at the early stages of matter dominated era, which appear in
alternative scenarios of cosmological dynamics in the context of modified
$f(R)$ gravitational theories, indicates an advantage of the theory for the
interpretation of late-time phenomenology.
