I am an ICREA Research Professor in Astrophysics and Cosmology. I work at the Institute of Cosmos Sciences and the Department of Quantum Physics and Astrophysics of the Universitat de Barcelona. I have been an ICREA Professor since 2005.
At present I am Scientific Director of the Institute of Cosmos Sciences, where I help managing our research activity together with the Institute Director Xavier Luri and Vice-Director Assumpta Parreño.
I enjoy searching for physical explanations of what we observe in the Universe. My interests range over the formation of galaxies and their large-scale distribution in space, dark matter and dark energy in the Universe, the intergalactic medium, the formation of massive black holes and the dynamics of nuclear regions of galaxies, and gravitational lensing as a probe to the nature of dark matter. When I moved to the Institut de Ciències del Cosmos in 2009, my research focused on the large-scale distribution of intergalactic gas probed by spectroscopic surveys of quasars in which hydrogen and heavy elements are observed in absorption. This reveals crucial clues on both the initial conditions of the Universe and the formation of galaxies. At present I looking at various techniques to inquire on the nature of dark matter, among them the observation of extremely magnified high-redshift stars close to the critical curves of clusters of galaxies acting as gravitational lenses, and the study of tidal streams of stars left by stellar systems orbiting the Milky Way galaxy. I am particularly interested in the hypothesis that dark matter is made of axion waves, which can solve at the same time a long-standing problem in particle physics known as the strong QCD problem. Below you can read more detailed descriptions of some of the research topics I have worked on:
Presentations to some of my recent professional seminars on my research:
February 16th 2021: Theoretical Physics Colloquium at the Department of Theoretical Physics, Tata Institute of Fundamental Research, Mumbai, India:
The nature of dark matter is one of the most important questions in modern cosmology. Recently, super-magnified images of stars have been detected in clusters of galaxies, where a single star can be detected with the Hubble Space Telescope at cosmological redshifts thanks to the large magnification factor. We will discuss how these highly magnified sources provide opportunities for testing the granularity of dark matter on small scales, for example, to find signatures of axion dark matter in the form of mini halos of asteroid mass.
Over the past several years, my research activity has focused on two
With former ICCUB graduate students Andreu Font-Ribera, Ignasi Pérez Ràfols, Lluís Mas-Ribas and Andreu Arinyo i Prats, I was involved in work on the intergalactic clouds of hydrogen called Damped Lyman Alpha Systems, which are identified in absorption in quasar spectra. This research is based on data from the Baryon Oscillation Spectroscopic Survey of the Sloan Digital Sky Survey III Collaboration.
In general, the SDSS
Collaboration resulted in excellent measurements of the Baryon
Acoustic Oscillation scale of the Universe at various redshifts, which
have greatly contributed to confirm the existence of an accelerated
rate of expansion of the Universe that is consistent with the
existence of a cosmological constant (this is usually referred to as
Dark Energy even though there is no evidence that it is different from
a cosmological constant so far). This result was achieved through the
study of galaxy correlations, and also correlations with absorption
spectra of intergalactic hydrogen and quasars.
At the same time, I have been involved in the investigation of the
nature of the dark matter using a variety of techniques: gravitational
lensing, dynamics of tidal streams, and experiments to directly detect
the QCD axion, the dark matter candidate favored by many cosmologists
These are some of my recent papers in these topics, with a summary of their results:
This is the Advanced Cosmology Course I am teaching at present in the ICCUB Master on Astrophysics, Particle Physics and Cosmology . This course is at present shared between me and Alessio Notari.
Some years I teach an informal course on introduction to present research in astrophysics, where we discuss and solve practical problems in class. These sessions are open to all students in the last two years of the Physics degree with an interest in astrophysics, and to master students and doctorate students. This is an informal course not counting for credit, where problems related to other courses can be discussed.
The method is that of participatory sessions, where students solve proposed problems with minimal guidance from the professor. This is not a series of lectures, but rather a sequence of independent sessions for learning to solve different problems and developing an approach to research in theoretical astrophysics. You therefore can attend some of the sessions without a requirement to having attended previous ones to follow the problem being solved. Students may also suggest problems to be ed. Please contact me for any questions you have.
Some interesting links:
Today's Astrophysics Preprints
Go to the Institut de Ciències del Cosmos page.
The schedule for the Institut de Ciències del Cosmos Seminars and Colloquia
Checkout today's Astronomy Picture of the Day