## Scientific Interests:## Theoretical Physics Professionally, I am a theoretical physicist. I do not
conceive myself working in a lab. I know that lab work is important,
but it is not my job. I prefer a blank piece of paper and a pen, and
perhaps (though not necessarily) a computer. With these simple tools
one can do a lot of things. Ask Albert Einstein. Other heroes
that I admire deeply are: Dirac, Heisenberg, Schrödinger and
Feynman. I do not admire them for their math, however
powerful it may have been; I admire them for their sublime physics,
for their unmatched ability to formulate profound concepts and ideas
that put theoretical physics in real contact with the most
intriguing phenomena of Nature, and for being so successful in it! I have other heroes outside Theoretical Physics, among them great
philosophers like Immanuel Kant, John Locke and David Hume. I also admire the writings of Bertrand
Russell, specially his magnificent ``History of Western
Philosophy''. ## Elementary Particles and Quantum Field Theory Modern Elementary Particle Theory is the application of
Quantum Field Theory to the phenomenology of the fundamental
interactions of Nature. I have been for a long time in this field.
To give you an idea, my first research work was the following: My interest in the field of Particle Physics has led me to organize (as full conference chairman) two international conferences on the subject, namely, Quantum Effects in the Minimal Supersymmetric Standard Model and the 4th International Symposium On Radiative Corrections (RADCOR 98). The RADCOR series of international conferences took its final name after I organized it in Barcelona in 1998. It was preceded by CRAD 96 in Cracow and followed by RADCOR 2000 in Carmel, California. At present, the {RADCOR} series is the most important meeting for researchers in the area of radiative corrections, and in general of people working in the application of Quantum Field Theory to the Phenomenology of Particle Physics in the Standard Model of the strong and electroweak interactions, and beyond, with crucial implications in the physics of the high energy colliders, like the LHC and the ILC. The most recent edition of this conference is RADCOR 2007. There is a whole RTN (Research Training Network) of theoretical high energy physicists, called HEPTOOLS (to which I belong, and act as a network representative in the UB), working on these matters.
## Cosmology and Gravitation:I was introduced in the field of Cosmology by Prof. Roberto D. Peccei (yes, the famous Peccei of the Peccei-Quinn symmetry) when I did my first postdoct at DESY (Deutches Elektronen Synchroton) in Hamburg, 1985-1987. One day, in a typical dark and snowy Hamburg's afternoon (I can assure you that at 4 pm it can be rather dark in Hamburg during winter), he would come to my office to talk on new research ideas. We had been working for months on Weinberg sum rules, low-energy theorems, QCD spectral functions etc. In fact, we had just finished to publish a rather relevant paper on the determination (for the first time in the literature, see Nucl. Phys. B281:1,1987) of the QCD vector and axial spectral functions, directly from tau-decay data obtained at DESY, and used them to compute the charged-neutral pion mass difference and other low-energy curiosities. But that afternoon was special, since Roberto wanted to talk with me on a very different subject of which I had no previous experience at all: he wanted to talk on Cosmology. He said, as if of a joke: what about trying to solve the Cosmological Constant Problem?...This is sooner said than done! Everybody knows that this is the toughest theoretical physics conundrum of all times, and that it probably hides the deepest and most coveted secrets on the interrelationship between Particle Physics, Gravitation and Cosmology. We could not solve it, of course, but we published a rather interesting, and well-known, paper on this matter, together with Christof Wetterich, with the intriguing title: Adjusting the cosmological constant dynamically: cosmons and a new force weaker than Gravity. This is how I started my investigations in cosmology, and since then the subject goes intermittently with me, I just cannot get rid of it! In the last sever years or so, my interest in this subject has grown more and more. However, I am not a ``pure'' cosmologist, I consider myself a particle physicist working in high energy physics, and also in the interface between Particle Physics and Cosmology. I try to convince people around me that the mutual implication between Particle Physics and Cosmology is one of the most interesting subjects of our times. This is probably the reason I have already organized two international conferences on this subject, the first one was the 22nd GIFT International Seminar on Theoretical Physics on the subject of Quantum Gravity, and the second was IRGAC 2006 (see also IRGAC 06B) on Quantum Theories and Renormalization Group in Gravity and Cosmology. |