Einstein's theory of relativity plays a major role in astrophysics, most notably in scenarios involving compact objects such as neutron stars and black holes. Those include gravitational collapse, gamma-ray burts, accretion, relativistic jets in active galactic nuclei, or the merger of compact neutron star and black hole binaries. Theoretical astrophysics has long relied on numerical simulations as a formidable way to improve our understanding of the dynamics of such astrophysical systems. Astronomers have long been scrutinizing these systems using the complete frequency range of the electromagnetic spectrum. Nowadays, they are also the main targets for ground-based laser interferometers of gravitational radiation. The direct detection of these elusive ripples in the curvature of spacetime, and the wealth of new information that could be extracted thereof, is one of the driving motivations of present-day research in relativistic astrophysics.

At the Relativistic Astrophysics Group of the Department of Astronomy and Astrophysics of the University of Valencia we conduct research devoted to understand the underlying physics and dynamics of some of the most representative scenarios in the field of Relativistic Astrophysics, namely relativistic jets (in active galactic nuclei, or in progenitors of gamma-ray bursts), and compact stellar objects (neutron stars and black holes), as well as to analyze the electromagnetic and gravitational radiation emitted from such sources. In order to achieve these goals our work strongly relies on the analysis of the most relevant physical processes, multidimensional numerical magneto-hydrodynamical and radiative transfer simulations. The constitutive areas of research of the group members and their broad objectives are as follows:

• Extragalactic jets. We investigate their stability properties and structure, as well as their formation, acceleration, and collimation mechanisms using three-dimensional magneto-hydrodynamical and emission simulations. We use data from observations across the whole electromagnetic spectrum, with special emphasis on radio continuum polarimetric VLBI observations, of multiple jets in AGN to investigate their emission properties and variability.
• Progenitors of gamma-ray bursts. We analyze the mechanism of formation and propagation of these celestial objects by means of multidimensional magneto-hydrodynamical simulations, paying particular attention to their emission properties.
• Physics of compact stars. We study the physics of neutrino production in dense superfluid matter, as well as neutrino transport in proto-neutron stars and in the accretion disks resulting from the merger of compact binaries. We investigate the thermal emission from magnetized neutron stars, as well as the thermal and magnetic evolution of these objects. The results of our models are compared with observations in order to fit the parameters of the models.
• Gravitational radiation. Using perturbative and full numerical relativity codes we compute the emission of gravitational radiation due to accretion processes on to compact objects, gravitational stellar core collapse to neutron stars and black holes, and pulsating and rapidly-rotating relativistic stars.