39,351 research outputs found
Cluster algebras in scattering amplitudes with special 2D kinematics
We study the cluster algebra of the kinematic configuration space
of a n-particle scattering amplitude restricted to the
special 2D kinematics. We found that the n-points two loop MHV remainder
function found in special 2D kinematics depend on a selection of
\XX-coordinates that are part of a special structure of the cluster algebra
related to snake triangulations of polygons. This structure forms a necklace of
hypercubes beads in the corresponding Stasheff polytope. Furthermore in , the cluster algebra and the selection of \XX-coordinates in special 2D
kinematics replicates the cluster algebra and the selection of \XX-coordinates
of two loop MHV amplitude in 4D kinematics.Comment: 22 page
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.
Synchronization in interacting Scale Free Networks
We study the fluctuations of the interface, in the steady state, of the
Surface Relaxation Model (SRM) in two scale free interacting networks where a
fraction of nodes in both networks interact one to one through external
connections. We find that as increases the fluctuations on both networks
decrease and thus the synchronization reaches an improvement of nearly
when . The decrease of the fluctuations on both networks is due mainly to
the diffusion through external connections which allows to reducing the load in
nodes by sending their excess mostly to low-degree nodes, which we report have
the lowest heights. This effect enhances the matching of the heights of low-and
high-degree nodes as increases reducing the fluctuations. This effect is
almost independent of the degree distribution of the networks which means that
the interconnection governs the behavior of the process over its topology.Comment: 13 pages, 7 figures. Added a relevant reference.Typos fixe
Differential Astrometry over 15 degrees
We observed the pair of radio sources 1150+812 and 1803+784 in November 1993
with a VLBI array, simultaneously recording at 8.4 and 2.3 GHz. We determined
the angular separation between the two sources with submilliarcsecond accuracy
by using differential techniques. This result demonstrates the feasibility of
high precision differential astrometry for radio sources separated in the sky
by almost 15 degrees, and opens the avenue to its application to larger samples
of radio sources.Comment: 6 pages, latex2e, 2 figures, To appear in the proceedings of the
EVN/JIVE Symposium No. 4, New Astronomy Reviews (eds. Garret, M. Campbell,
R., and Gurvits, L.
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