One of the main themes of our project is the analytical and numerical study of the so-called Relativistic Positioning Systems (RPS). A collaborator of our group (B. Coll) proposed this research line a decade ago. We will study in depth topics such as bifurcation and minimisation of positioning errors, and in the longer term gravimetry. We will also try to study – in its relativistic aspects–  satellite navigation based on pulsar observation. The European Space Agency has repeatedly shown its interest in relativistic positioning by setting up working groups and organising conferences.

We are also conducting the following studies within the framework of the theory of General Relativity (GR): (1) intrinsic characterisation of some physically significant solutions of Einstein’s equations (spherically symmetric solutions, cosmological models, etc.) and of the gravitational radiation states (Bel-Robinson tensor), and (2) study of the concepts of total intrinsic linear 4-momentum and angular 4-momentum of the universe, and application to the characterisation of universes that could be created by quantum vacuum fluctuations.

In addition, part of our team is working on the study of non-linear anisotropies of the cosmic microwave background using numerical simulations. Following this line, we intend to study the secondary Rees-Sciama, Sunyaev-Zel´dovich and lensing anisotropies and, above all, we are interested in the non-linear superposition of these effects to compare it with recent observational data obtained within the framework of the SPT (South Pole Telescope) and ACT (Atacama Cosmology Telescope) projects at very small angular scales. This topic requires complicated simulations that are being carried out in collaboration with the main researcher (H.M.P Couchman) and other members (R. Thacker) of the International Hydra Consortium for the development of numerical simulations of structure formation. In-house equipment and equipment from the UV Computing Centre are being used.

Finally, the nature of dark energy is a current topic of debate in which we want to participate by trying to study different alternatives to vacuum energy or of a certain dynamical scalar field (quintessence). Among others, we intend to analyse possible explanations based on: (a) the energy associated with certain vector fields (vector-tensor theories), (b) inhomogeneous universes within the framework of GR, and (c) negative pressure associated with the gravitational interaction between certain structures populating the universe.

We have always considered that theoretical developments and simulations complement each other when it comes to explaining observations and that, therefore, when working on gravitation, direct collaboration between theoretical researchers with a solid geometrical background and those with extensive experience in developing simulations is highly desirable. The composition of our group guarantees this collaboration, which has already yielded good results and which we are confident will continue to do so. Not all our work will be carried out within the framework of General Relativity, since some cosmological observations, such as anomalies in the angular spectrum of the microwave background and the luminosity-redshift relation of type Ia supernovae, suggest the existence of new fields in the framework of certain generalisations of Einstein's theory of gravitation (scalar-tensor, vector-tensor, tensor-tensor theories, etc.). These alternative theories are currently being seriously investigated and we join this trend with moderation. We also join the opposite trend, which tries to explain the so-called dark sector through application models of Einstein's theory, without additional fields.

Until 2015, we were funded by the FIS2012-33582 project of MINECO.

Collaborators

• Roberto Dale Valdivia - Miguel Hernández University of Elche
• Màrius Fullana Alfonso - Universitat Politècnica de València

Investigation activities