123 research outputs found
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
Meisterhaft erklärt, humorvoll geschrieben : Top-Physikerin führt durch höherdimensionale gekrümmte Räume
Rezension zu: Lisa Randall : Verborgene Universen : Eine Reise in den extradimensionalen Raum, Fischer Verlag, Frankfurt 2006, ISBN-13: 978-3-10-062805-3, 448 Seiten, 19,90 Euro
Classifications of Twin Star Solutions for a Constant Speed of Sound Parameterized Equation of State
We explore the possible mass radius relation of compact stars for the
equation of states with a first order phase transition. The low density matter
is described by a nuclear matter equation of state resulting from fits to
nuclear properties. A constant speed of sound parametrization is used to
describe the high density matter phase with the speed of sound .
A classification scheme of four distinct categories including twin star
solutions, i. e. solutions with the same mass but differing radii, is found
which are compatible with the pulsar mass constraint.
We show the dependence of the mass and radius differences on the transition
parameters and delineate that higher twin star masses are more likely to be
accompanied by large radius differences. These massive twin stars are generated
by high values of the discontinuity in the energy density and the lowest
possible values of the transition pressure that still result in masses of at the maximum of the hadronic branch.Comment: 8 pages, 9 figure
Cosmological implications of a Dark Matter self-interaction energy density
We investigate cosmological constraints on an energy density contribution of
elastic dark matter self-interactions characterized by the mass of the exchange
particle and coupling constant. Because of the expansion behaviour in a
Robertson-Walker metric we investigate self-interacting dark matter that is
warm in the case of thermal relics. The scaling behaviour of dark matter
self-interaction energy density shows that it can be the dominant contribution
(only) in the very early universe. Thus its impact on primordial
nucleosynthesis is used to restrict the interaction strength, which we find to
be at least as strong as the strong interaction. Furthermore we explore dark
matter decoupling in a self-interaction dominated universe, which is done for
the self-interacting warm dark matter as well as for collisionless cold dark
matter in a two component scenario. We find that strong dark matter
self-interactions do not contradict super-weak inelastic interactions between
self-interacting dark matter and baryonic matter and that the natural scale of
collisionless cold dark matter decoupling exceeds the weak scale and depends
linearly on the particle mass. Finally structure formation analysis reveals a
linear growing solution during self-interaction domination; however, only
non-cosmological scales are enhanced.Comment: 14 pages, 14 figures; version published in Phys. Rev.
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