9,323 research outputs found
Production rates for hadrons, pentaquarks and , and di-baryon in relativistic heavy ion collisions by a quark combination model
The hadron production in relativistic heavy ion collisions is well described
by the quark combination model. The mixed ratios for various hadrons and the
transverse momentum spectra for long-life hadrons are predicted and agree with
recent RHIC data. The production rates for the pentaquarks , and the di-baryon are estimated, neglecting
the effect from the transition amplitude for constituent quarks to form an
exotic state.Comment: The difference between our model and other combination models is
clarified. The scaled transverse momentum spectra for pions, kaons and
protoms at both 130 AGeV and 200 AGeV are given, replacing the previous
results in transverse momentum spectr
When resources collide: Towards a theory of coincidence in information spaces
This paper is an attempt to lay out foundations for a general theory of coincidence in information spaces such as the World Wide Web, expanding on existing work on bursty structures in document streams and information cascades. We elaborate on the hypothesis that every resource that is published in an information space, enters a temporary interaction with another resource once a unique explicit or implicit reference between the two is found. This thought is motivated by Erwin Shroedingers notion of entanglement between quantum systems. We present a generic information cascade model that exploits only the temporal order of information sharing activities, combined with inherent properties of the shared information resources. The approach was applied to data from the world's largest online citizen science platform Zooniverse and we report about findings of this case study
Global gyrokinetic simulations of the impact of magnetic island on ion temperature gradient driven turbulence
The effect of island width on the multi-scale interactions between magnetic
island (MI) and ion temperature gradient (ITG) turbulence has been investigated
based on the global gyrokinetic approach. It is found that the coupling between
the island and turbulence is enhanced when the MI width (w) becomes larger. A
vortex flow that is highly sensitive to the width of the magnetic island can be
triggered, ultimately resulting in a potent shear flow and a consequent
reduction in turbulent transport. The shearing rate induced by the vortex flow
is minimum at the O-point while it is maximum at both of the two reconnection
points of the island, i.e., the X-points, regardless of the island width. There
exists a nonmonotonic relationship between zonal flow (ZF) amplitude and island
width, showing that the ZF is partially suppressed by medium-sized MIs whereas
enhanced in the case of large island. A larger MI can tremendously damage the
ITG mode structure, resulting in higher turbulent transport at the X-point
whereas a lower one at the O-point, respectively. Such phenomenon will be less
distinct at very small island widths below w/a =8% (a is the minor radius),
where it shows that turbulence near the X-point is hardly affected although it
is still suppressed inside the island. Furthermore, the influence of different
island sizes on turbulence transport level is also discussed
Extreme Sensitivity of Superconductivity to Stoichiometry in FeSe (Fe1+dSe)
The recently discovered iron arsenide superconductors, which display
superconducting transition temperatures as high as 55 K, appear to share a
number of general features with high-Tc cuprates, including proximity to a
magnetically ordered state and robustness of the superconductivity in the
presence of disorder. Here we show that superconductivity in Fe1+dSe, the
parent compound of the superconducting arsenide family, is destroyed by very
small changes in stoichiometry. Further, we show that non-superconducting
Fe1+dSe is not magnetically ordered down to low temperatures. These results
suggest that robust superconductivity and immediate instability against an
ordered magnetic state should not be considered as intrinsic characteristics of
iron-based superconducting systems, and that Fe1+dSe may present a unique
opportunity for determining which materials characteristics are critical to the
existence of superconductivity in high Tc iron arsenide superconductors and
which are not.Comment: Updated to reflect final version and include journal referenc
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