1,434 research outputs found
Symmetry Energy Effects on the Mixed Hadron-Quark Phase at High Baryon Density
The phase transition of hadronic to quark matter at high baryon and isospin
density is analyzed. Relativistic mean field models are used to describe
hadronic matter, and the MIT bag model is adopted for quark matter. The
boundaries of the mixed phase and the related critical points for symmetric and
asymmetric matter are obtained. Due to the different symmetry term in the two
phases, isospin effects appear to be rather significant. With increasing
isospin asymmetry the binodal transition line of the (T,\rho_B) diagram is
lowered to a region accessible through heavy ion collisions in the energy range
of the new planned facilities, e.g. the FAIR/NICA projects. Some observable
effects are suggested, in particular an "Isospin Distillation" mechanism with a
more isospin asymmetric quark phase, to be seen in charged meson yield ratios,
and an onset of quark number scaling of the meson/baryon elliptic flows. The
presented isospin effects on the mixed phase appear to be robust with respect
to even large variations of the poorly known symmetry term at high baryon
density in the hadron phase. The dependence of the results on a suitable
treatment of isospin contributions in effective QCD Lagrangian approaches, at
the level of explicit isovector parts and/or quark condensates, is finally
discussed.Comment: 14 two column pages, 14 figures, new results with other hadron EoS.
Accepted for publication in Phys.Rev.
Analysis of dilepton production in Au+Au collisions at sqrt(s_NN)=200 GeV within the Parton-Hadron-String Dynamics (PHSD) transport approach
We address dilepton production in Au+Au collisions at sqrt(s_NN)=200 GeV by
employing the parton-hadron-string dynamics (PHSD) off-shell transport
approach. Within the PHSD one goes beyond the quasiparticle approximation by
solving generalized transport equations on the basis of the off-shell
Kadanoff-Baym equations for the Green's functions in the phase-space
representation. The approach consistently describes the full evolution of a
relativistic heavy-ion collision from the initial hard scatterings and string
formation through the dynamical deconfinement phase transition to the
quark-gluon plasma (QGP) as well as hadronization and to the subsequent
interactions in the hadronic phase. {With partons described in the PHSD by the
dynamical quasiparticle model (DQPM) - matched to reproduce lattice QCD results
in thermodynamic equilibrium} - we calculate, in particular, the dilepton
radiation from partonic interactions through the reactions q+qbar->gamma^*,
q+qbar->gamma^*+g and q+g->gamma^*+q (qbar+g->gamma^*+qbar) in the early stage
of relativistic heavy-ion collisions. By comparing our results to the data from
the PHENIX Collaboration, we study the relative importance of different
dilepton production mechanisms and point out the regions in phase space where
partonic channels are dominant. Furthermore, explicit predictions are presented
for dileptons within the acceptance of the STAR detector system and compared to
the preliminary data.Comment: 11 pages, 10 figures. arXiv admin note: substantial text overlap with
arXiv:1107.340
Classification of integrable Weingarten surfaces possessing an sl(2)-valued zero curvature representation
In this paper we classify Weingarten surfaces integrable in the sense of
soliton theory. The criterion is that the associated Gauss equation possesses
an sl(2)-valued zero curvature representation with a nonremovable parameter.
Under certain restrictions on the jet order, the answer is given by a third
order ordinary differential equation to govern the functional dependence of the
principal curvatures. Employing the scaling and translation (offsetting)
symmetry, we give a general solution of the governing equation in terms of
elliptic integrals. We show that the instances when the elliptic integrals
degenerate to elementary functions were known to nineteenth century geometers.
Finally, we characterize the associated normal congruences
Nuclear fragmentation: sampling the instabilities of binary systems
We derive stability conditions of Asymmetric Nuclear Matter () and
discuss the relation to mechanical and chemical instabilities of general
two-component systems. We show that the chemical instability may appear as an
instability of the system against isoscalar-like rather than isovector-like
fluctuations if the interaction between the two constituent species has an
attractive character as in the case of . This leads to a new kind of
liquid-gas phase transition, of interest for fragmentation experiments with
radioactive beams.Comment: 4 pages (LATEX), 3 Postscript figures, improved version, added
reference
Constraining the Symmetry Energy: A Journey in the Isospin Physics from Coulomb Barrier to Deconfinement
Heavy Ion Collisions (HIC) represent a unique tool to probe the in-medium
nuclear interaction in regions away from saturation. In this work we present a
selection of reaction observables in dissipative collisions particularly
sensitive to the isovector part of the interaction, i.e. to the symmetry term
of the nuclear Equation of State (EoS). At low energies the behavior of the
symmetry energy around saturation influences dissipation and fragment
production mechanisms. We will first discuss the recently observed Dynamical
Dipole Radiation, due to a collective neutron-proton oscillation during the
charge equilibration in fusion and deep-inelastic collisions. Important Iso-EOS
effects are stressed. Reactions induced by unstable 132Sn beams appear to be
very promising tools to test the sub-saturation Isovector EoS. New Isospin
sensitive observables are also presented for deep-inelastic, fragmentation
collisions and Isospin equilibration measurements (Imbalance Ratios). The high
density symmetry term can be derived from isospin effects on heavy ion
reactions at relativistic energies (few AGeV range), that can even allow a
``direct'' study of the covariant structure of the isovector interaction in the
hadron medium. Rather sensitive observables are proposed from collective flows
and from pion/kaon production. The possibility of the transition to a mixed
hadron-quark phase, at high baryon and isospin density, is finally suggested.
Some signatures could come from an expected ``neutron trapping'' effect. The
importance of studying violent collisions with radioactive beams from low to
relativistic energies is finally stressed.Comment: 15 pages, 5 figures, Int.Workshop on Nuclear Dynamics in Heavy Ion
Reactions and Neutron Stars, Beijing Normal Univ. July 07, to appear in
Int.Journ.Modern Physics E (2008
Kepler detection of a new extreme planetary system orbiting the subdwarf-B pulsator KIC10001893
KIC10001893 is one out of 19 subdwarf-B (sdB) pulsators observed by the
Kepler spacecraft in its primary mission. In addition to tens of pulsation
frequencies in the g-mode domain, its Fourier spectrum shows three weak peaks
at very low frequencies, which is too low to be explained in terms of g modes.
The most convincing explanation is that we are seeing the orbital modulation of
three Earth-size planets (or planetary remnants) in very tight orbits, which
are illuminated by the strong stellar radiation. The orbital periods are
P1=5.273, P2=7.807, and P3=19.48 hours, and the period ratios P2/P1=1.481 and
P3/P2=2.495 are very close to the 3:2 and 5:2 resonances, respectively. One of
the main pulsation modes of the star at 210.68 {\mu}Hz corresponds to the third
harmonic of the orbital frequency of the inner planet, suggesting that we see,
for the first time in an sdB star, g-mode pulsations tidally excited by a
planetary companion. The extreme planetary system that emerges from the Kepler
data is very similar to the recent discovery of two Earth-size planets orbiting
the sdB pulsator KIC05807616 (Charpinet et al. 2011a).Comment: 6 pages, 5 figures, accepted for publication in Astronomy and
Astrophysic
Collective Dipole Bremsstrahlung in Fusion Reactions
We estimate the dipole radiation emitted in fusion processes. We show that a
classical bremsstrahlung approach can account for both the preequilibrium and
the thermal photon emission. We give an absolute evaluation of the
pre-equilibrium component due to the charge asymmetry in the entrance channel
and we study the energy and mass dependence in order to optimize the
observation. This dynamical dipole radiation could be a relevant cooling
mechanism in the fusion path. We stress the interest in experiments with the
new available radioactive beams.Comment: 4 pages (LATEX), 4 Postscript figures, minor text modification
Water requirements of floodplain rivers and fisheries: existing decision support tools and pathways for development
Fisheries / Rivers / Flood plains / Hydrology / Ecology / Models / Decision support tools / Environmental impact assessment / Methodology / Databases
Signals of dynamical and statistical process from IMF-IMF correlation function
In this paper we briefly discuss about a novel application of the IMFIMF correlation function to the physical case of binary massive projectile-like (PLF) splitting for dynamical and statistical breakup/fission in heavy ion collisions at Fermi energy. Theoretical simulations are also shown for comparisons with the data. These preliminary results have been obtained for the reverse kinematics reaction 124Sn+64Ni at 35 AMeV that was studied using the forward part of CHIMERA detector. In that reaction a strong competition between a dynamical and a statistical components and its evolution with the charge asymmetry of the binary break up was already shown. In this work we show that the IMF-IMF correlation function can be used to pin down the timescale of the fragments production in binary fission-like phenomena. We also made simulations with the CoMDII model in order to compare to the experimental IMF-IMF correlation function. In future we plan to extend these studies to different reaction mechanisms and nuclear systems and to compare with different theoretical transport simulations
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