I will describe an approach to compute correlation functions of primordial fluctuations that is based on symmetries and singularities. It borrows tools from other areas of theoretical physics, like the S-matrix program of particle physics, as well as the conformal bootstrap. Using this approach, I will present some new results for inflationary three and four-point functions of scalars and...
We study the geometrical instability arising in multi-field models of inflation with negatively-curved field space. We analyse how the homogeneous background evolves in presence of geometrical destabilisation, and show that, in simple models, a kinematical backreaction effect takes place that shuts off the instability. We also follow the evolution of the unstable scalar fluctuations. We show...
I will begin by introducing the stochastic formalism for inflation. I will give some motivation for using the stochastic approach and then explain why we may want to consider situations that violate slow roll. I will explain the requirements for stochastic inflation to be a valid approach and discuss whether they are still appropriate when we are away from slow roll. The two requirements that...
Inflation provides a dynamical mechanism to produce the primordial density perturbations that seed the formation of structure in the Universe through gravitational collapse. However, during the inflationary phase, the Universe is in a nearly homogeneous and low-entropy state, which must eventually give rise to the dense thermal plasma of the standard hot big bang. This transition, known as...
I will discuss the post-inflation dynamics of multi-field models involving nonminimal couplings. In particular I will describe the results of lattice simulations used to capture significant nonlinear effects like backreaction and rescattering. I will show how we can we extract the effective equation of state and typical time-scales for the onset of thermalization, quantities that could affect...
We consider possible detection of nonclassicality of primordial gravitational waves (PGWs) by applying Hanbury Brown - Twiss (HBT) interferometry to cosmology. We characterize the nonclassicality of PGWs in terms of sub-Poissonian statistics that can be measured by the HBT interferometry. We show that the presence of matter fields during inflation makes us possible to detect nonclassical PGWs...
We study the formation of primordial black holes (PBH) in a single field inflection point model of inflation wherein the effective potential is expanded up to the sextic order and the inversion symmetry is imposed such that only even power terms are retained in the potential. By working with a near inflection point in the potential, we find that PBHs can be produced in our scenario in a very...
In a first order electroweak phase transition bubbles of Higgs phase
expand into the symmetric phase. Particles hitting a bubble wall
cause friction and slow down the expansion. In some models this can be
insufficient to compensate the pressure difference between the two
phases. Then the bubble wall would accelerate indefinitely, it would 'run
away'. However, particles crossing the...
We will discuss new probes of non-Gaussianity in the distribution of CMB temperature anisotropies as well as that of collapsed objects such as galaxies and clusters. Going beyond polyspectra, we will focus on CMB/LSS probability distribution functions and discuss how the structure of the pre-Big Bang era can be partially encoded in it.
Hidden fields present during single-field inflation can affect CMB observables through quantum vacuum fluctuations. Besides the renormalization of background quantities, loop corrections of these fields induce Planck-suppressed logarithmic runnings in correlation functions of curvature and tensor perturbations. In this talk we consider the impact of a large number of such field degrees of...
Recent swampland conjectures highlight again the importance of finding viable scenarios for inflation that are not strictly single-field. In particular, one may wonder whether there are multi-field inflationary scenarios that have a similar phenomenology to single field inflation. We present a family of exact models of inflation - dubbed Orbital Inflation - in which the multi-field effects are...
Observations of Planck's CMB favours a canonical slow-roll single-field scenario for inflation. However, simple multi-field extensions can also explain the current data, and on top some of the existing anomalies not accounted for by the canonical scenario. We present our search for multi-field-motivated extra degrees of freedom in the context of an effective single field theory with a varying...
In this talk I will introduce tools for the construction of effective field theories (EFTs) that involve the breaking of spacetime symmetries. Nowadays, symmetry breakdown is part and parcel of the study of EFTs, with group theory allowing us to derive the most generic action for the Goldstone bosons—but only if the group is internal. When spacetime symmetries are broken, the game becomes much...
The viability of a given model for inflation is determined not only by the form of the inflaton potential, but also by the initial inflaton field configuration. In many models, otherwise well-motivated inflaton field configurations fail to induce inflation, or fail to produce sufficient inflation to solve the horizon problem. In this talk, we propose a mechanism which enables inflation to...
I will discuss a recent construction wherein an effective de Sitter spacetime appears as a non-supersymmetric AdS vacuum decays into the supersymmetric vacuum. Four-dimensional observers are localized on a spherical brane which nucleates to facilitate the decay. The expansion of the brane bubble then leads to an effective four-dimensional de Sitter space. This construction side-steps the...
Primordial SU(2) gauge fields coupled to axions can contribute to the physics of inflation. Their rich phenomenology and unique observational features, e.g., chiral primordial gravitational waves, turned this class of models to a hot topic of study since their discovery in 2011. In this talk, I will briefly review the models in this class, which so far have been studied in the literature....
The coupling of an axion-like particle driving inflation to the Standard Model particle content through a Chern-Simons term generically sources a dual production of massless helical gauge fields and chiral fermions. We demonstrate that the interplay of these two components results in a highly predictive baryogenesis model, which requires no further ingredients beyond the Standard Model. If the...
In this talk I will consider an inflationary universe with non-Abelian gauge fields and axion fields that are in part identified with the standard model of particle physics.
In particular I consider possibilities of an enlarged color group with extra heavy quarks that solves the strong CP problem. When the heavy quarks are integrated out below the Peccei-Quinn symmetry breaking scale, they...
