3,201 research outputs found
Physics with first LHCb data
The LHCb experiment is designed for hadronic flavour physics and will look
for New Physics manifestations in the decay of charm and bottom hadrons
abundantly produced at the LHC. All parts of the LHCb physics programme can be
embarked on with the expected statistics to be collected during the first
2010-2011 physics run at = 7 TeV. We present first preliminary
results on strangeness production, and demonstrate, using the few nb-1 of
already collected data, the potential for initial measurements in heavy-flavour
physics.Comment: 9 pages, 7 figures, to appear in the proceedings of the "Physics at
LHC 2010" conference, June 7-12, 2010, DESY, Hamburg, German
Vanishing thetanulls and hyperelliptic curves
Let be the moduli space of curves of genus with a
level-2 structure. We prove here that there is always a non hyperelliptic
element in the intersection of four thetanull divisors in .
We prove also that for all , each component of the hyperelliptic
locus in is a connected component of the intersection of
thetanull divisors.Comment: 13 page
Adaptive multiresolution computations applied to detonations
A space-time adaptive method is presented for the reactive Euler equations
describing chemically reacting gas flow where a two species model is used for
the chemistry. The governing equations are discretized with a finite volume
method and dynamic space adaptivity is introduced using multiresolution
analysis. A time splitting method of Strang is applied to be able to consider
stiff problems while keeping the method explicit. For time adaptivity an
improved Runge--Kutta--Fehlberg scheme is used. Applications deal with
detonation problems in one and two space dimensions. A comparison of the
adaptive scheme with reference computations on a regular grid allow to assess
the accuracy and the computational efficiency, in terms of CPU time and memory
requirements.Comment: Zeitschrift f\"ur Physicalische Chemie, accepte
Ambiguities in gravitational lens models: impact on time delays of the source position transformation
The central ambition of the modern time delay cosmography consists in
determining the Hubble constant with a competitive precision. However,
the tension with obtained from the Planck satellite for a spatially-flat
CDM cosmology suggests that systematic errors may have been
underestimated. The most critical one probably comes from the degeneracy
existing between lens models that was first formalized by the well-known
mass-sheet transformation (MST). In this paper, we assess to what extent the
source position transformation (SPT), a more general invariance transformation
which contains the MST as a special case, may affect the time delays predicted
by a model. To this aim we use pySPT, a new open-source python package fully
dedicated to the SPT that we present in a companion paper. For axisymmetric
lenses, we find that the time delay ratios between a model and its SPT-modified
counterpart simply scale like the corresponding source position ratios, , regardless of the mass profile
and the isotropic SPT. Similar behavior (almost) holds for non-axisymmetric
lenses in the double image regime and for opposite image pairs in the quadruple
image regime. In the latter regime, we also confirm that the time delay ratios
are not conserved. In addition to the MST effects, the SPT-modified time delays
deviate in general no more than a few percent for particular image pairs,
suggesting that its impact on time-delay cosmography seems not be as crucial as
initially suspected. We also reflected upon the relevance of the SPT validity
criterion and present arguments suggesting that it should be reconsidered. Even
though a new validity criterion would affect the time delays in a different
way, we expect from numerical simulations that our conclusions will remain
unchanged.Comment: 15 pages, 14 figure
The EXoplanetary Circumstellar Environments and Disk Explorer (EXCEDE)
We present an overview of the EXoplanetary Circumstellar Environments and
Disk Explorer (EXCEDE), selected by NASA for technology development and
maturation. EXCEDE will study the formation, evolution and architectures of
exoplanetary systems, and characterize circumstellar environments into stellar
habitable zones. EXCEDE provides contrast-limited scattered-light detection
sensitivities ~ 1000x greater than HST or JWST coronagraphs at a much smaller
effective inner working angle (IWA), thus enabling the exploration and
characterization of exoplanetary circumstellar disks in currently inaccessible
domains. EXCEDE will utilize a laboratory demonstrated high-performance Phase
Induced Amplitude Apodized Coronagraph (PIAA-C) integrated with a 70 cm
diameter unobscured aperture visible light telescope. The EXCEDE PIAA-C will
deliver star-to-disk augmented image contrasts of < 10E-8 and a 1.2 L/D IWA or
140 mas with a wavefront control system utilizing a 2000-element MEMS DM and
fast steering mirror. EXCEDE will provide 120 mas spatial resolution at 0.4
microns with dust detection sensitivity to levels of a few tens of zodis with
two-band imaging polarimetry. EXCEDE is a science-driven technology pathfinder
that will advance our understanding of the formation and evolution of
exoplanetary systems, placing our solar system in broader astrophysical
context, and will demonstrate the high contrast technologies required for
larger-scale follow-on and multi-wavelength investigations on the road to
finding and characterizing exo-Earths in the years ahead
Advances and Applications of Experimental Measures to Test Behavioral Saving Theories and a Method to Increase Efficiency in Binary and Multiple Treatment Assignment
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