26,637 research outputs found
How does breakup influence the total fusion of Li at the Coulomb barrier?
Total (complete + incomplete) fusion excitation functions of Li on
Co and Bi targets around the Coulomb barrier are obtained using
a new continuum discretized coupled channel (CDCC) method of calculating
fusion. The relative importance of breakup and bound-state structure effects on
total fusion is particularly investigated. The effect of breakup on fusion can
be observed in the total fusion excitation function. The breakup enhances the
total fusion at energies just around the barrier, whereas it hardly affects the
total fusion at energies well above the barrier. The difference between the
experimental total fusion cross sections for Li on Co is notably
caused by breakup, but this is not the case for the Bi target.Comment: 9 pages, 9 figures, Submitted to Phys. Rev.
Thermal Conductivity and Chiral Critical Point in Heavy Ion Collisions
Background: Quantum Chromodynamics is expected to have a phase transition in
the same static universality class as the 3D Ising model and the liquid-gas
phase transition. The properties of the equation of state, the transport
coefficients, and especially the location of the critical point are under
intense theoretical investigation. Some experiments are underway, and many more
are planned, at high energy heavy ion accelerators. Purpose: Develop a model of
the thermal conductivity, which diverges at the critical point, and use it to
study the impact of hydrodynamic fluctuations on observables in high energy
heavy ion collisions. Methods: We apply mode coupling theory, together with a
previously developed model of the free energy that incorporates the critical
exponents and amplitudes, to construct a model of the thermal conductivity in
the vicinity of the critical point. The effect of the thermal conductivity on
correlation functions in heavy ion collisions is studied in a boost invariant
hydrodynamic model via fluctuations, or noise. Results: We find that the closer
a thermodynamic trajectory comes to the critical point the greater is the
magnitude of the fluctuations in thermodynamic variables and in the 2-particle
correlation functions in momentum space. Conclusions: It may be possible to
discern the existence of a critical point, its location, and thermodynamic and
transport properties near to it in heavy ion collisions using the methods
developed here.Comment: 36 pages, 8 figures. Version published in Phys.Rev.C86, 054911
(2012). It contains some minor improvements with respect to v1: further
clarifications, small changes on figures and two extra reference
Multi-wavelength differential astrometry of the S5 polar cap sample
We report on the status of our S5 polar cap astrometry program. Since 1997 we
have observed all the 13 radio sources of the complete S5 polar cap sample at
the wavelengths of 3.6 cm, 2 cm and 7 mm. Images of the radio sources at 3.6
and 2 cm have already been published reporting morphological changes.
Preliminary astrometric analyses have been carried out at three frequencies
with precisions in the relative position determination ranging from 80 to 20
microarcseconds. We report also on the combination of our phase-delay global
astrometry results with the microarcsecond-precise optical astrometry that will
be provided by future space-based instruments.Comment: 2 pages. 1 figure. Proceedings of the 7th European VLBI Network
Symposium held in Toledo, Spain on October 12-15, 2004. Editors: R.
Bachiller, F. Colomer, J.-F. Desmurs, P. de Vicente (Observatorio Astronomico
Nacional), p. 323-324. Needs evn2004.cl
Debye Potentials for Maxwell and Dirac Fields from a Generalisation of the Killing-Yano Equation
By using conformal Killing-Yano tensors, and their generalisations, we obtain
scalar potentials for both the source-free Maxwell and massless Dirac
equations. For each of these equations we construct, from conformal
Killing-Yano tensors, symmetry operators that map any solution to another.Comment: 35 pages, plain Te
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