497 research outputs found
Strange Dibaryons in Neutron Stars and in Heavy-Ion Collisions
The formation of dibaryons with strangeness are discussed for the interior of
neutron stars and for central relativistic heavy-ion collisions. We derive
limits for the properties of H-dibaryons from pulsar data. Signals for the
formation of possible bound states with hyperons at BNL's Relativistic
Heavy-Ion Collider (RHIC) are investigated by studying their weak decay
patterns and production rates.Comment: 7 pages, 4 figures, invited talk given at the VII International
Conference on Hypernuclear and Strange Particle Physics, Torino, Italy,
October 23-27, 200
Signals of the QCD Phase Transition in the Heavens
The modern phase diagram of strongly interacting matter reveals a rich structure at high-densities
due to phase transitions related to the chiral symmetry of quantum chromodynamics (QCD) and
the phenomenon of color superconductivity. These exotic phases have a significant impact on
high-density astrophysics, such as the properties of neutron stars, and the evolution of astrophysical systems as proto-neutron stars, core-collapse supernovae and neutron star mergers. Most recent pulsar mass measurements and constraints on neutron star radii are critically discussed.
Astrophysical signals for exotic matter and phase transitions in high-density matter proposed recently in the literature are outlined. A strong first order phase transition leads to the emergence of a third family of compact stars besides white dwarfs and neutron stars. The different microphysics of quark matter results in an enhanced r-mode stability window for rotating compact stars compared to normal neutron stars. Future telescope and satellite data will be used to extract signals from phase transitions in dense matter in the heavens and will reveal properties of the phases of dense QCD. Spectral line profiles out of x-ray bursts will determine the mass-radius ratio of compact stars. Gravitational wave patterns from collapsing neutron stars or neutron star mergers will even be able to constrain the stiffness of the quark matter equation of state. Future astrophysical data can therefore provide a crucial cross-check to the exploration of the QCD phase diagram with the heavy-ion program of the CBM detector at the FAIR facility
What is so special about strangeness in hot matter?
The production of strange particles in a hot medium as produced in collisions
of heavy ions is considered one of the most important signals for the phase
transition to a quark-gluon plasma. In the first part of this lecture, the
theoretical description of strangeness production in hot matter is outlined for
a gas of quarks and gluons and for a hadronic gas and its impact on the
deconfinement phase transition. Then in the second part, constraints from the
underlying chiral symmetry of Quantum Chromodynamics (QCD) are utilized to
extract signals with strangeness for the chiral phase transition in hot matter.Comment: 22 pages, 9 figures, to be published as topical review for Journal of
Physics
Strangelets and Strange Quark Matter
The properties of finite lumps of strange quark matter (strangelets) with
emphasis on the two scenarios of producing strange matter in relativistic heavy
ion collisions are summarized. As an outlook, the possibility of short-lived
strange composites and charmed matter are discussed for coming heavy ion
experiments.Comment: 8 pages, 3 figures, uses elsevier style and epsf.sty, invited talk
given at the International Conference on Hypernuclear and Strange Particle
Physics (HYP'97), October 13-18, Brookhaven National Laboratory, USA, to be
published in Nuclear Physics
Pulsar kicks by anisotropic neutrino emission from quark matter
We discuss an acceleration mechanism for pulsars out of their supernova
remnants based on asymmetric neutrino emission from quark matter in the
presence of a strong magnetic field. The polarized electron spin fixes the
neutrino emission from the direct quark Urca process in one direction along the
magnetic field. We calculate the magnetic field strength which is required to
polarize the electron spin as well as the required initial proto-neutron star
temperature for a successfull acceleration mechanism. In addition we discuss
the neutrino mean free paths in quark as well as in neutron matter which turn
out to be very small. Consequently, the high neutrino interaction rates will
wash out the asymmetry in neutrino emission. As a possible solution to this
problem we take into account effects from colour superconductivity.Comment: 6 pages, 3 figures, poster contribution at the conference "Nuclear
Physics in Astrophysics III",Dresden,March 26-31,200
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