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

Detecting quark matter in the early universe by gravitational waves

For large baryochemical potential, strongly interacting matter might undergo a first order phase transition at temperatures T ~ 100-200 MeV. Within standard cosmology, however, the chemical potential is assumed to be very small leading to a crossover. We discuss implications of a first order QCD transition at high chemical potential being consistent with current observations. In this contribution we concentrate on effects on the gravitational wave spectrum. There are other interesting cosmological signals as a modification of the power spectrum of dark matter, the production of stellar black holes, and the seeds for the extragalactic magnetic fields which we briefly address also.Comment: 10 pages, talk given at the symposium "Advances in Nuclear Physics in Our Time", Goa, India, Nov. 28 - Dec. 2, 201

Quark-hadron mixed phases in protoneutron stars

We consider the possible formation of the quark hadron mixed phase in protoneutron stars. We discuss two cases: the first one, corresponding to a vanishingly small value of the surface tension of quark matter, is the well known mixed phase in which the global electric charge neutrality condition is imposed. In turn, this produces a non-constant pressure mixed phase. In the second case, corresponding to very large values of the surface tension, the charge neutrality condition holds only locally. However, the existence in protoneutron star matter of an additional globally conserved charge, the lepton number, allows for a new type of non-constant pressure mixed phase. We discuss the properties of the new mixed phase and the possible effects of its formation during the evolution of protoneutron stars.Comment: 6 pages, 2 figures, talk given at the the International Conference SQM2009, Buzios, Rio de Janeiro, Brazil, Sep.27-Oct.2, 200

New Class of Compact Stars at High Density

We discuss the equation of state for cold, dense quark matter in perturbation theory, and how it might match onto that of hadronic matter. Certain choices of the renormalization scale correspond to a strongly first order chiral transition, and may generate a new class of small and very dense quark stars. The results for the mass-radius relation are compatible with the recent determination of the mass and the radius of an isolated neutron star by Pons et al.Comment: Latex, 7 pages, 4 figures. Presented at the International Conference on Statistical QCD, Bielefeld, Germany, 26-30 August 2001. Requires espcrc1.st

Phase Transition to Hyperon Matter in Neutron Stars

Recent progress in the understanding of the high density phase of neutron stars advances the view that a substantial fraction of the matter consists of hyperons. The possible impacts of a highly attractive interaction between hyperons on the properties of compact stars are investigated. We find that a hadronic equation of state with hyperons allows for a first order phase transition to hyperonic matter. The corresponding hyperon stars can have rather small radii of R=8 km.Comment: 4 pages, 4 figures, figures modified, text updated and rewritten, final version, Phys. Rev. Lett. in pres