Inflaton candidates: from string theory to particle physics

TL;DR

This paper reviews various inflationary models from string theory and particle physics, analyzing their consistency with Planck data and potential for future observational tests.

Contribution

It introduces new inflationary scenarios derived from string theory, supergravity, and grand unified theories, linking fundamental physics to cosmological observations.

Findings

All models align with Planck data

Predictions include scalar spectral index and tensor-to-scalar ratio

Future observations can distinguish between models

Abstract

Cosmic inflation is the cornerstone of modern cosmology. In particular, following the Planck mission reports presented in 2015 regarding cosmic microwave background (CMB), there is an increasing interest in searching for inflaton candidates within fundamental theories and to ultimately test them with future CMB data. This thesis presents inflationary models using a methodology that can be described as venturing top-down or bottom-up along energy scales. In the top-down motivation, we study inflationary scenarios in string theory and supergravity (SUGRA), namely with (multiple) 3-forms, Dirac-Born-Infeld Galileon model, a string field theory setup and $\mathcal{N}=1$ SUGRA $\alpha-$attractor models. In the bottom-up motivation, we construct a grand unified theory based inflationary model with an additional conformal symmetry and study not only inflation but also provide predictions related to particle physics. Our research work includes various classes of inflation driven by scalar fields under a canonical, non-canonical and induced gravity frameworks. All these models are consistent with Planck data, supported by key primordial cosmological parameters such as the scalar spectral index $n_{s}$, the tensor to scalar ratio $r$, together with the primordial non-Gaussianities. Future probes aiming to detect primordial gravitational waves and CMB non-Gaussianities can further help to distinguish between them.