|Microlensing is the amplification
of the light of a background star due to the transit on the line of
sight of a massive object, which acts as a gravitational lens. The
lens can be another star or a brown dwarf. The light curve of the
background star has a typical bell shape, with a duration of a few
days. Since microlensing events are very rare, millions of source
stars must be monitored every night in order to detect them.
Microlensing can be used to
search for extrasolar planets. In fact, if the lens is a
star accompanied by a planet, the light curve of the source contains
an anomaly like a secondary peak or a dip. Our group is part of the
MiNDSTEp collaboration, looking for extrasolar planets in
microlensing observations toward the bulge of our Galaxy. Every year
we are leading observations at the
Danish telescope at ESO, La Silla (Chile) and at
Salerno University Observatory. We have also
developed an advanced code for automatic real-time modeling of
anomalous microlensing events (RTModel).
Recently, these observations are being supported by the
Kepler satellites, which are
dedicating an important part of their observing time to microlensing.
|Gravitational lensing by black holes
leads to the spectacular formation of infinite sequences of images
very close to the shadow cast by the black hole in the sky. The
direct observation of this shadow and of higher order images could
soon be accessible by incoming instruments in several
electromagnetic bands. The black hole in the center of our Galaxy
provides the best candidate for these new observations that will
open a new era in gravitational physics.
Scaling laws in galaxies are
important to understand the mechanisms for the formation of the
first galaxies. We have found a new law relating the mass of the
massive black hole hosted in the center of galaxies and the kinetic
energy of stars in the corresponding bulge. It appears that galaxies
follow an analogue of the H-R diagram.
|Early universe cosmology
investigates the first instants of our universe. General Relativity
is not sufficient to describe the hot quantum universe close to the
big bang. String theory and other quantum gravity theories suggest
the possibility that the big bang was actually not the beginning of
time, but just a transition from a previous pre-big bang collapsing
universe to our observed expanding universe.
The Baryon Asymmetry problem
refers to the observed asymmetry in the Universe between baryonic
and antibaryonic matter. Since the Big Bang should have produced
equal amounts of matter and antimatter, it is then expected that
some still unkonw mechanism must have acted differently for matter
and antimatter during the Universe evolution. This mechanism cannot
be explaind within the standard model of particle physics and
cosmology, and in fact, modern theories aimed at solving the problem
of the baryon asymmetry are based on physics beyond these models.