Thesis

Modified gravity: linear and non-linear cosmological probes

• Call:

  IDPASC Portugal - PHD Programme 2019

• Academic Year:

  2019 / 2020

• Domains:

  General Relativity | Cosmology | Astrophysics

• Supervisor:

  Noemi Frusciante

• Co-Supervisor:

  Francisco Lobo

• Institution:

  Faculdade de Ciências - Universidade de Lisboa

• Host Institution:

  Faculdade de Ciências - Universidade de Lisboa

• Abstract:

  The recent cosmic acceleration is challenging the theory of General Relativity (GR) at the basis of the standard cosmological model, LCDM. This led people to propose in place of the cosmological constant (L), new alternatives in the form of dynamical dark energy(DE) or theories of modified gravity(MG). Collective properties of these proposals are: the dynamics of the graviton is modified at large scales; at intermediate scales the modifications are regulated by screening mechanisms, which suppress the modifications on smaller scales. Ongoing and upcoming cosmological surveys will provide highly precision data allowing to test gravity with an unprecedented accuracy and the new era of multi-messenger astronomy opened new possibilities for testing gravity. On the theoretical side, while many Modified Gravity models are still allowed by type Ia supernova (SNIa) and Cosmic Microwave Background (CMB) data; structure formation can help us to distinguish among them and the standard scenario, thanks to their signatures on the matter power spectrum, in the linear and mildly non-linear regimes. Thus, to fully exploit the available data at our disposal, e.g. the galaxy clustering, CMB lensing and, most importantly, weak lensing data, one has to scrutinize at all scales the properties of DE/MG models, in particular the effects of screening mechanisms on structures formation. The integration of screening and non-linearities effects in numerical investigations is still an open issue. The goal of the PhD project will be to unveil the real nature of the theory of gravity. To achieve this, the student will apply theoretical modeling and numerical methods to construct new tools to test linear/non-linear effects of modified gravity. The analysis tools developed by the student are expected to be used in the upcoming ESA Euclid mission in which the host institution has a leading role. In order to ensure a successful PhD, this project contains theoretical and numerical elements that are flexible such that they can fit with the student’s skills and expertise.