Jes Madsen

Physics and astrophysics of strange quark matter

3-flavor quark matter (strange quark matter; SQM) can be stable or metastable for a wide range of strong interaction parameters. If so, SQM can play an important role in cosmology, neutron stars, cosmic ray physics, and relativistic heavy-ion collisions. As an example of the intimate connections between astrophysics and heavy-ion collision physics, this Chapter gives an overview of the physical properties of SQM in bulk and of small-baryon number strangelets; discusses the possible formation, destruction, and implications of lumps of SQM (quark nuggets) in the early Universe; and describes the structure and signature of strange stars, as well as the formation and detection of strangelets in cosmic rays. It is concluded, that astrophysical and laboratory searches are complementary in many respects, and that both should be pursued to test the intriguing possibility of a strange ground state for hadronic matter, and (more generally) to improve our knowledge of the strong interactions.

Probing strange stars and color superconductivity by r-mode instabilities in millisecond pulsars

r-mode instabilities in rapidly rotating quark matter stars (strange stars) lead to specific signatures in the evolution of pulsars with periods below 2.5 msec, and may explain the apparent lack of very rapid pulsars. Existing data seem consistent with pulsars being strange stars with a normal quark matter phase surrounded by an insulating nuclear crust. In contrast, quark stars in a color-flavor-locked phase are ruled out. Two-flavor color superconductivity is marginally inconsistent with pulsar data.

Neutrino decoupling in the early universe

A calculation of neutrino decoupling in the early Universe, including full Fermi-Dirac statistics and electron mass dependence in the weak reaction rates, is presented. We find that after decoupling the electron neutrinos contribute 0.83% more to the relativistic energy density than in the standard scenario, where neutrinos are assumed not to share the heating from

Small deviations from the R[SUP]1/4[/SUP] law, the fundamental plane, and phase densities of elliptical galaxies

{\mathit{e}}^{\ifmmode\pm\else\textpm\fi{}}

HOW TO IDENTIFY A STRANGE STAR

annihilation. The corresponding number for \ensuremath{\mu} and \ensuremath{\tau} neutrinos is 0.41%. This has the consequence of modifying the primordial

Strangelet propagation and cosmic ray flux

^{4}\mathrm{He}

Strange Quark Matter in Physics and Astrophysics

abundance by \ensuremath{\Delta}Y=+1.0\ifmmode\times\else\texttimes\fi{}

Shell model versus liquid drop model for strangelets

{10}^{\mathrm{\ensuremath{-}}4}

Strangelets as cosmic rays beyond the Greisen-Zatsepin-Kuzmin cutoff.

, and the cosmological mass limit on light neutrinos by 0.2\char21{}0.5 eV.

Large nucleation distances from impurities in the cosmological quark-hadron transition.

The light profiles of elliptical (E) galaxies are known to display small systematic deviations (0.1-0.2 mag.) from the R^1/4 law. In this paper we show that the senses and amplitudes of these departures can be naturally accounted for by a simple distribution function constructed on the basis of statistical mechanics of violent relaxation. As a consequence, detailed light-profiles can be used to infer about the central potentials of E galaxies (the only free shape parameter of our model). Furthermore, the small deviations have recently been shown to correlate with luminosity, L. This observation entails a slight breaking of the generally assumed structural homology between E galaxies. Using our model we parametrize this broken homology by establishing a correlation between a suitably normalized central potential and luminosity. The non-homology means that a basic assumption in the interpretation of the Fundamental Plane (FP) breaks down, and with it the conclusions derived from it. Instead, by assuming that M/L is independent of luminosity, we derive a relation akin to the FP directly from our correlation. This implies that the FP may have a simple stellar dynamical origin. We can reproduce the observed Carlberg-Kormendy relation for the central phase-space densities (f_c) of E galaxies of identical structure, f_c = L^-2.35, but non-homology changes it to a much weaker dependence (f_c = L^-1.5 for constant M/L) which would imply that the central phase-space densities of ellipticals are comparable to those of spiral galaxies. Thus dissipationless merging is consistent with the FP, although HST observations, notably the presence of nuclear embedded disks, indicate that the assumptions behind our model break down for the nuclei of faint E galaxies in which dissipative processes seem to be important.