42,438 research outputs found
Situations in traffic - how quickly they change
Spatio-temporal correlations of intensity of traffic are analysed for one
week data collected in the motorway M-30 around Madrid in January 2009. We
found that the lifetime of these correlations is the shortest in the evening,
between 6 and 8 p.m. This lifetime is a new indicator how much attention of
drivers is demanded in given traffic conditions.Comment: 9 pages, 6 figure
SUSY and Dark Matter Constraints from the LHC
The ability of the LHC to make statements about the dark matter problem is
considered, with a specific focus on supersymmetry. After reviewing the current
strategies for supersymmetry searches at the LHC (in both CMS and ATLAS), some
key ATLAS studies are used to demonstrate how one could establish that SUSY
exists before going on to measure the relic density of a neutralino WIMP
candidate. Finally, the general prospects for success at the LHC are
investigated by looking at different points in the MSSM parameter space.Comment: Talk given at the XLIrst Rencontres de Moriond session devoted to
Electroweak Interactions And Unified Theories in March 2006, to be published
in the associated proceedings. 10 pages, 8 figure
Chiral Symmetry and s-wave Low-Lying Meson-Baryon Resonances
The wave meson-baryon scattering is analyzed for the isospin-strangeness
and sectors, in a Bethe-Salpeter coupled channel
formalism incorporating Chiral Symmetry. For both sectors, four channels have
been considered: , , , and ,
, , , respectively. The needed two particle
irreducible matrix amplitudes are taken from lowest order Chiral Perturbation
Theory in a relativistic formalism. There appear undetermined low energy
constants, as a consequence of the renormalization of the amplitudes, which are
obtained from fits to the available data: elastic phase-shifts, and cross sections and to
mass-spectrum, the elastic and
--matrices and to the
cross section data. The position and residues of the complex poles in the
second Riemann sheet of the scattering amplitude determine masses, widths and
branching ratios of the (1535) and (1650) and
(1405) and (1670) resonances, in reasonable agreement with
experiment. A good overall description of data, from threshold up to around 2
GeV is achieved despite the fact that three-body channels have not been
explicitly included.Comment: 5 Pages, 2 figures, invited contribution to Focus Session on Nature
of Threshold N*, to be published in Proceedings of Nstar 2002, Pittsburgh,
USA, October 9-12, 2002 (World Scientific
Spontaneous, collective coherence in driven, dissipative cavity arrays
We study an array of dissipative tunnel-coupled cavities, each interacting
with an incoherently pumped two-level emitter. For cavities in the lasing
regime, we find correlations between the light fields of distant cavities,
despite the dissipation and the incoherent nature of the pumping mechanism.
These correlations decay exponentially with distance for arrays in any
dimension but become increasingly long ranged with increasing photon tunneling
between adjacent cavities. The interaction-dominated and the
tunneling-dominated regimes show markedly different scaling of the correlation
length which always remains finite due to the finite photon trapping time. We
propose a series of observables to characterize the spontaneous build-up of
collective coherence in the system.Comment: 9 pages, 4 figures, including supplemental material (with 4 pages, 1
figure). This is a shorter version with some modifications in the
supplemental material (a gap in the proof was closed and calculations
significantly generalized and improved
Faint emission lines in the Galactic H II regions M16, M20 and NGC 3603
We present deep echelle spectrophotometry of the Galactic {\hii} regions M16,
M20 and NGC 3603. The data have been taken with the Very Large Telescope
Ultraviolet-Visual Echelle Spectrograph in the 3100 to 10400 \AA range. We have
detected more than 200 emission lines in each region. Physical conditions have
been derived using different continuum and line intensity ratios. We have
derived He, C and O abundances from pure recombination
lines as well as abundances from collisionally excited lines for a large number
of ions of different elements. We have obtained consistent estimations of the
temperature fluctuation parameter, {\ts}, using different methods. We also
report the detection of deuterium Balmer lines up to D (M16) and to
D (M20) in the blue wings of the hydrogen lines, which excitation
mechanism seems to be continuum fluorescence. The temperature fluctuations
paradigm agree with the results obtained from optical CELs and the more
uncertain ones from far IR fine structure CELs in NGC 3603, although, more
observations covering the same volume of the nebula are necessary to obtain
solid conclusions.Comment: 22 pages, 13 Tables, 7 Figures. Accepted for publication by MNRA
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