Quintessential Inflation attempts to account for the tunings of the Hot Big Bang and for Dark Energy, using a single degree of freedom and a single theoretical framework, with the aim to avoid the extreme fine tuning needed for the cosmological constant in LambdaCDM. However, in the past the task proved to be very difficult. We will present how modern developments, e.g. in the context of...
We consider an eight-dimensional Einstein-Yang-Mills theory to study whether Yang-Mills instantons formed in extra-dimensions can trigger cosmic inflation in our four-dimensional spacetime. We observe that the Yang-Mills instantons in extra dimensions and homogeneous in four dimensional spacetime act as a cosmological constant for the four-dimensional Einstein gravity. As a result,we study...
We consider the most minimal scale invariant extension of the standard model that allows for successful radiative electroweak symmetry breaking and inflation. The framework involves an extra scalar singlet, that plays the role of the inflaton, and is compatibile with current experimental bounds owing to the non-minimal coupling of the latter to gravity.
This inflationary scenario predicts a...
Current measurements of the Higgs boson and top quark mass favor metastability of the electroweak vacuum in the Standard Model. This raises some questions when we consider the evolution of our universe: how did it end up in such an energetically disfavored state? Why it remained there during inflation? These problems can be addressed by assuming for the Higgs a direct coupling with the...
I will present a minimal extension of the Standard Model that addresses dark matter, the strong CP problem, the smallness of neutrino masses, baryogenesis and primordial inflation. The model contains a new U(1) symmetry and a single new physics scale of the order of 10^11 GeV. Dark matter is made of axions, whose mass in predicted to be in a narrow range, which will be probed in the near...
I will discuss the appeal of pseudo-Goldstone bosons (pGBs) for the generation of scales in Early Universe cosmology. In particular, I will show how Goldstone Inflation addresses the inflationary hierarchy problem (the tension between the Lyth bound and the scale of inflation as preferred by CMB anisotropies), while avoiding the problems with trans-Planckian scales that are typically...
In the conventional Big Bang picture, our current (perturbative) theories of gravity are not powerful enough to reliably capture the earliest moments of our Universe – they break down due to the large curvatures and high energies. An alternative early Universe scenario is a 'non-singular bounce’, in which an initially contracting phase bounces into an expanding Universe like the one we live in...
The discovery of the accelerated expansion of the universe triggered an intense activity in infrarred modifications of gravity with an additional scalar degree of freedom. This scalar is then used to replace the cosmological constant as the responsible for the cosmic acceleration. A common problem in these models is that this scalar must be very light to have cosmological effects today....
Most existing theories of dark energy and/or modified gravity, involving a scalar degree of freedom, can be conveniently described within the framework of the Effective Theory of Dark Energy. After reviewing this approach, I will extend it to consider Higher-Order Scalar Tensor Theories and discuss their degeneracy and phenomenological viability at the linear level.
The "Effective theory of dark energy" is a simple, general and effective way to bridge theory and observations in dark energy and modified gravity scenarios based on a single scalar field. I will illustrate its application to models that admit a kinetic mixing between matter and the scalar field, which I’ll call "Kinetic Matter Mixing". I will argue that this is a truly physical effect...
Constraining the dark energy equation of state, w, as well as modified growth of large structures predicted by alternatives to GR, are among the primary science goals of ongoing and future cosmological surveys. We derive the theoretical prior covariance for w predicted by a general class of theories of a scalar field dark energy (Horndeski theories). This is achieved by generating a large...
In an attempt to explain dark energy numerous models and modified gravity theories have been constructed in order to better describe current cosmological observations. An obvious way to modify gravity is to introduce a new field other than the metric and make dark energy a dynamical component. In this talk I will present Generalized Einstein-Aether, a vector-tensor theory of gravity where the...
We present an application of the equation of state approach to dark sector perturbations as a comprehensive phenomenological framework to understand the evolution of perturbations in dark energy and modified gravity models. The
approach is based on the observation that any modified gravity theory can be recast into an effective dark energy fluid. By eliminating the internal degree of freedom...
In the next few years, we are going to probe the low-redshift universe with unprecedented accuracy. Among the various fruits that this will bear, it will greatly improve our knowledge of the dynamics of dark energy, though for this there is a strong theoretical preference for a cosmological constant. We assume that dark energy is described by the so-called Effective Field Theory of Dark...
Cosmological inflation is one of the leading paradigms for explaining the physical conditions that prevailed in the early Universe. It consists in a phase of very high energy accelerated expansion that solves the hot big bang model problems. When combined with quantum mechanics, it also provides a causal mechanism for generating cosmological fluctuations on large scales.
In this talk I will...
The Wiener filter has emerged as a standard tool for the inference of high dimensional signals, such as the large scale structures and cosmic microwave background (CMB) problems. Some particularly key applications of the Wiener filter in CMB data analysis include power spectrum estimation, map-making and the reconstruction of lensing potential. We present a new fast and robust iterative...
The last decades witnessed huge progress in understanding the large-scale structure of the Universe. While homogeneous and isotropic on the largest scales, the matter and galaxy distributions display complex patterns on smaller scales where we observe elongated filaments, compact clusters and volume-filling underdense regions. These features are not captured by studies of two-point statistics...
The current and future galaxy surveys give us several challenge both in terms of data management and interpretation. The interpretation is made particularly complex by observational limitations, such as selection and foreground issues, and the extreme dynamical non-linearity of the galaxies. Such problems are generally taken into account a posteriori in the analysis, and are covered by putting...
To extract cosmological information from large-scale galaxy clustering, we need accurate modeling of the relationship between dark matter and galaxies (galaxy bias). Recently, field-theory techniques have been used to provide a new description of galaxy biasing in terms of renormalised operators and counter terms, i.e. to build quantities that are not UV sensitive. We test these definitions of...
It is known that cold dark matter candidates lead to the structuring of matter on scales much smaller than typical galaxies. This clustering translates into a very large population of subhalos in galaxies, which must impact predictions for indirect searches of annihilating dark matter. I present a model (arXiv:1610:02233) consistently describing the subhalo population in a dynamically...
Although the existence of Dark Matter (DM) is by now well-established thanks to a variety of observations on many different scales, its nature is still unknown and so are many of its most basics properties, such as its lifetime. Moreover, even if obvious arguments require that most of the DM is stable on timescales of (at least) the lifetime of the universe, a fraction of it could be in the...
I will talk about a DM scenario in which the self-scattering rate today is regulated by kinematics and/or the abundance ratio, through the mass-splitting of two nearly degenerate states, emphasising the implications of the considered models and their prospect of solving astrophysical small-scale structure problems.
We consider a model of a holographic braneworld universe in which a cosmological fluid occupies a 3+1 dimensional brane located at the boundary of the asymptotic AdS bulk. We combine the AdS/CFT correspondence and the second Randall-Sundrum
(RSII) model to establish a relationship between the RSII braneworld cosmology and
the boundary metric induced by the time dependent bulk geometry. In the...
