374 research outputs found
Colored condensates deep inside neutron stars
It is demonstrated how in the absence of solutions for QCD under conditions
deep inside compact stars an equation of state can be obtained within a model
that is built on the basic symmetries of the QCD Lagrangian, in particular
chiral symmetry and color symmetry. While in the vacuum the chiral symmetry is
spontaneously broken, it gets restored at high densities. Color symmetry,
however, gets broken simultaneously by the formation of colorful diquark
condensates. It is shown that a strong diquark condensate in cold dense quark
matter is essential for supporting the possibility that such states could exist
in the recently observed pulsars with masses of 2 .Comment: 4 pages, 2 figures, Proceedings of "Wigner 111 -- Colourful \& Deep",
Budapest, Hungary, 11-13 November 201
X(3872) as a D-D* molecule bound by quark exchange forces
The Bethe-Salpeter equation for the T-Matrix of D-D* scattering is solved
with a meson-meson potential that results from 2nd order Born approximation of
quark exchange processes. This potential turns out to be complex and energy
dependent due to the pole contribution from the coupling to the intermediate
J/psi-rho meson pair propagator. As a consequence, a bound state with a mass
close to 3.872 GeV occurs in the J/psi-rho continuum. This result suggests that
quark exchange forces may provide the solution to the puzzling question for the
origin of the interaction which leads to a binding of D and D* mesons in the
X(3872) state.Comment: 6 pages, 3 figures, contribution to the Proceedings of the 28th
Max-Born-Symposium on "Three days on quarkyonic island", Wroclaw, Poland, May
19-21, 201
Mass-radius constraints for compact stars and a critical endpoint
We present two types of models for hybrid compact stars composed of a quark
core and a hadronic mantle with an abrupt first order phase transition at the
interface which are in accordance with the latest astrophysical measurements of
two 2 M_sun pulsars. While the first is a schematic one, the second one is
based on a QCD motivated nonlocal PNJL model with density-dependent vector
coupling strength. Both models support the possibility of so called twin
compact stars which have the same mass but different radius and internal
structure at high mass (~2 M_sun), provided they exhibit a large jump \Delta
\epsilon in the energy density of the first order phase transition fulfilling
\Delta \epsilon/\epsilon_crit > 0.6. We conclude that the measurement of
high-mass twin stars would support the existence of a first order phase
transition in symmetric matter at zero temperature entailing the existence of a
critical end point in the QCD phase diagram.Comment: 7 pages, 2 figures, 1 table, prepared for the Proceedings of the 8th
International Workshop on "Critical Point and Onset of Deconfinement",March
11 to 15, 2013, Napa, California, US
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