Research Line: Gravitation and Cosmology
Lead Researcher(s): Cássius Anderson Miquele de Melo, Iara Tosta e Melo, Jean Carlos Coelho Felipe, Rodrigo Rocha Cuzinatto
Description:

The standard theory for describing gravitational interaction is General Relativity (GR). It predicts the manifestation of gravitational effects through spacetime curvature. GR describes astrophysical objects such as neutron stars, black holes, orbital effects unexplained by Newtonian mechanics (such as Mercury’s secular perihelion shift), light ray deflection (producing gravitational lenses), and redshift effects of radiation near strong fields (which affect GPS system calibration, for example). Gravitational waves (GW) are another prediction of GR, dramatically confirmed by the detection of GW emitted during the coalescence of black hole pairs and neutron stars by the LIGO-VIRGO collaboration. GR also offers a model for large-scale universe dynamics, Cosmology. This explains the cosmic microwave background radiation, the origin and abundance of light elements, and large-scale structure of the universe.

Despite all its success, general relativity and its resulting cosmology have limitations. Notably, GR predicts singularities and is a non-renormalizable field theory. In turn, the standard cosmological model is unable to offer a cause for the Big Bang (without the complement of the inflationary hypothesis) or to elucidate the nature of the universe’s dark sector.

In this research line, we contribute to the study of gravitation and its cosmological consequences in various aspects. Examples include:

  1. The description of gravitation as first and second-order gauge theory for Lorentz and Poincaré symmetry groups (this subject connects with the “Field Theory and Gauge Theories” research line);
  2. The extension of GR to scalar-tensor theories, which include new fields alongside the metric tensor for describing gravitation;
  3. The extension of GR with the inclusion of higher derivative terms in curvature invariants;
  4. Black hole physics (causal structure, geodesics, thermodynamics, shadows) in the context of modified gravity models and/or generalized electrodynamics (in the case of charged black holes);
  5. The description of gravitational waves emitted by coalescing binary systems in the context of modified gravity models;
  6. Study of cosmic inflation in the context of extended gravitation models, their formal aspects (such as frame equivalence, etc.) and their observational constraints (using Planck satellite data);
  7. The study of the current universe with modified gravity models (e.g., involving higher derivatives or variable physical couplings) and modified matter (e.g., unified model of dark matter and dark energy).