Research

Non-linear effects in gravity

Einstein’s theory of gravity is a very non-linear theory. However, the objects in the Universe with the strongest gravitational field, black holes, appear to be very simple. Even the noise that they emit when two of them collide seems to be described by a simple ‘‘chirp’’ noise, followed by a ringing composed of several notes, with different intensities. Why does the merger process look so apparently simple? What decides with which notes does the resulting black hole ring? I want to understand this and several other questions better. This requires a combination of analytical and perturbation theory techniques with computational methods to solve Einstein equations numerically.

Tests of General Relativity

General Relativity is the best theory of gravity so far: it has been used to succesfully predict gravitational waves, the abundance of elements in the Universe or the formation of the Sun and other stars. However in the innermost part of black holes, it is doomed to fail. There are several proposals for modified gravity theories, as well as theories that attempt to reconcile gravitation with quantum mechanics. All of these models must be tested against our current and future observations. I work on understanding better how compact objects and gravitational waves would interact in some of these modified theories.

Singularities and Cauchy horizons

Astrophysical black holes are rotating: some of them do it very fast, and some of them do it slowly. However, they share a very weird inner structure: their classical description has a surface called a Cauchy horizon. This means that even if we had all the information about the location and trajectory of each particle one milisecond after the Big Bang, we would not be able to predict what happens inside that surface. We know that this picture is not stable, and that in the process that forms these objects something will prevent a Cauchy horizon from forming (this conjecture is known as the Strong Cosmic Censorship). I am interested in using numerical methods to simulate the process of the formation of a rotating black hole all the way up to the singularity itself.