Speaker
Alessandro Drago
(Universita' di Ferrara)
Description
Abstract:
Over the last few years, a strong synergy has been developing among
research areas apparently quite separated, offering the possibility to
investigate several crucial questions in hadronic and nuclear physics,
astrophysics, and gravitational physics from complementary viewpoints. The
main goal of this research is to discover the composition of matter at
supra-nuclear density, which, in turn, would allow us to map in a more
complete way the phase diagram of matter under extreme conditions, by
complementing the information at high temperature and low baryonic density
that is already investigated in heavy-ion collision experiments at
energies larger than about 100 AGeV, such as the ones performed by ALICE
at CERN. A few fundamental questions wait to be answered, in particular:
- At which baryonic densities do quarks start to deconfine? Is there at
all a deconfinement critical density?
- Is there a critical point in the phase diagram of matter at large
densities and temperatures?
- Is Witten’s hypothesis about the absolute stability of strange quark
matter realized in compact stars?
- Are supernova explosions and gamma-ray bursts associated to phase
transitions in dense matter?
These questions are deeply connected with a fundamental problem: at which
densities can strange hadrons be produced and what is their impact on the
equation of state of matter? The solution of this problem has become
extremely urgent after the discovery of compact stars having a mass of at
least two solar masses: the so-called “hyperon puzzle” has to do with the
difficulties in explaining the stability of very massive stars while
taking into account the production of strange hadrons, as requested by the
present laboratory data. The solution of this problem, crucial both for
nuclear-hadronic physics and for astrophysics, is at the moment unknown
and it could indicate that the interaction of strange hadrons is deeply
different from what is known at the moment or that deconfined quarks
appear at least in the most massive stars.
In order to answer these questions, the collaboration among various
research areas is not only useful, but rather essential. The reason is
that results obtained only from laboratory experiments or only from X-ray
satellites would not be able to address the questions above. For instance,
the discovery that Witten’s hypothesis is indeed realized in Nature can
come only from: a) laboratory experiments revealing at which densities
strange hadronic matter starts being formed; b) theoretical studies
investigating the implications of strangeness deposition on the stability
of matter and, obviously, c) the measurement of masses and radii of
compact stars via observations from gravitational-wave detectors and X-ray
satellites. Separately, each of these investigations could provide some
hints, but cannot give a definitive answer.
