Inflation and Modified Gravity in the era of Euclid and the SKA

The next decade will see the outcome of two major experiments dedicated
to cosmology: the European Euclid space mission, in which Belgium is
involved since 2013 and the Square Kilometre Array (SKA), which will be
the largest radio-telescope ever built. The Euclid telescope is designed to
understand the source responsible for the accelerating expansion of the
Universe, referred as Dark Energy (DE). The nature of DE is still a mystery
and could involved modifications of gravity. Euclid has also important
secondary objectives. Among them, it will constrain the initial conditions of
the Universe, especially in the context of cosmic inflation models. The SKA
will probe the large scale distribution of galaxies, the weak gravitational
lensing, the epoch of reionisation (EOR) and the cosmic dawn (CD), with
very interesting perspectives for cosmology, in particular for inflation, dark
energy and modified gravity.
The first objective of the project is to deliver robust forecasts for inflation
with Euclid, SKA and future CMB experiments (COrE+) (i) on the standard
parameters describing the shape of the primordial scalar power spectrum,
(ii) on slow-roll parameters characterizing the inflationary regime, (iii) on all
193 single-field scenarios listed in the ASPIC library, (iv) on a series of
extended inflation models with features.
The second goal is to deliver numerical simulation tools to be used for the
model selection and forecasts in the context of the preparatory phase of the
Euclid mission. A series of codes we developed in the context of modified
gravity will be improved, extended to deliver Euclid observables and
likelihoods and validated in coordination with the Euclid Theory Working
Group. Joint Euclid and SKA forecasts will be calculated for a series of
modified gravity models involving a scalar field coupled to matter and a
screening mechanism, including f(R), chameleons, symmetrons, dilaton and
K-mouflage models.