Research in the Particle Theory group
The latest cosmological data from the Planck satellite on the Cosmic Microwave Background radiation, together with observations from supernovae and the large-scale structure (LSS) favour the now called standard cosmological Lambda-Cold-Dark-Matter model (LCDM), complemented with the inflationary scenario to generate the large scale structures, such as galaxies and stars, that we observe today. The LCDM is a remarkably successful phenomenological model, which however requires specific ingredients that cannot be described in terms of the Standard Model (SM) of elementary particles and General Relativity. In particular, introduces the concept of dark energy (DE): a form of energy with negative pressure, which has a repulsive gravitational effect, causing the accelerated expansion of the universe that we observe today. It also introduces dark matter (DM): a form of matter composed mostly of non-baryonic particles, which interact very weakly with the SM fields. Finally, inflation requires the introduction of at least one scalar field, the inflaton, with specific properties to solve the horizon and flatness problems as well as provide the seeds for LSS formation.
Our research focuses mainly on understanding the nature and origin of acceleration in the universe, both at early epochs (inflation) as well as today (dark energy), in terms of a fundamental theory of gravity. In particular we work on inflation in string theory and supergravity, as well as on its implications from a four dimensional field theory point of view. Important for observations is to determine observables that can allow us to pin down the properties of the fluid responsible for inflation and its primordial fluctuations as well as to distinguish them among different models.
We are also interested in understanding whether the dark sector of the universe, dark matter and dark energy, can have a common origin, for example in terms of a coupled system or via modifications of general relativity.