PhD thesis proposals

PROJECT 1: The Standard Model Higgs, inflation and the nature of gravity

The properties of the recently discovered Higgs boson together with the absence of new physics at the LHC allows us to speculate about consistently extending the Standard Model of particle physics all the way up to the Planck scale while staying in the perturbative regime. In this context, the Standard Model Higgs non-minimally coupled to gravity could be responsible for the generation of the primordial spectrum of curvature perturbations seeding structure formation and the emergence of the electroweak scale via non-perturbative effects. Interestingly enough, the predictions of this general paradigm are sensitive to the different incarnations of gravity (metric, unimodular, Palatini, Einstein-Cartan, Weyl…), opening the door to test its fundamental nature with collider experiments and future cosmological probes such as LiteBIRD.

This thesis will carry out a systematic exploration of the relation between the Higgs field and gravity in the absence of new degrees of freedom beyond the electroweak scale. In particular, we will attempt to identify a self-consistent set of asymptotically scale-invariant theories to be embedded in an eventual completion of gravity and able to describe the full evolution of the Universe while potentially solving the long-standing hierarchy problem. To this end, we will follow a multidisciplinary approach combining theoretical and particle physics requirements such as unitarity and radiative stability with cosmological and astrophysical observations. Candidates with a strong motivation and curiosity on the relation between the electroweak and the Planck scale are strongly encouraged to apply.

Supervisor: Javier Rubio
Co-supervisor: Ilidio Lopes

Please do not hesitate to contact me if you need further details!

PROJECT 2: Collapsed structures in scalar-tensor theories of gravity

Many modified gravity theories introduce novel scalar degrees of freedom in order to explain inflation, dark energy and dark matter. Interestingly enough, these fields could play an important role not only on the dynamics of the Universe as a whole but also on the evolution of collapsed structures such as galaxies or stars. In particular, the presence of scalar degrees of freedom gives rise, almost generically, to new attractive forces able to modify the standard gravitational collapse of General Relativity. Depending on the precise couplings to matter, this modification could allow for unexpected phenomena such as for the formation of primordial black holes during radiation domination or the existence of neutron stars with scalar hairs on spherically symmetric and static backgrounds.

This thesis will consider the role of conformal and disformal interactions on the formation and evolution of compact structures in the early and late Universe. By using analytical and numerical techniques, we will study aspects such as the dynamical development of the screening mechanism, the formation and stability of structures with scalar hair, the impact of fifth forces on asteroseismology or the potential emission and gravitational memory of scalar waves. Our studies are expected to be relevant for current and future cosmological surveys such as GAIA, LIGO or LISA.

Supervisors: Javier Rubio and Ilidio Lopes

Please do not hesitate to contact me if you need further details!