47,886 research outputs found
Bares 2.0 wave buoy and sustainable buoy network
The aim of this article is to show the operation of the Bares 2.0 wave buoy
and the Bares network developed by HCTech. In the marine sector it is highly important
to know the state of the sea for applications such as the construction of ports,
the study of the impact of waves in coastal areas, the development and calibration
of forecasting wave models, the knowledge of the state of the maritime navigation
channels, etc. Some of the great difficulties that exist in order to obtain the information
of ocean waves is the high cost of the buoys, installation and maintenance. The
Bares network aims to cover areas of high oceanographic interest, the target is a
sustainable network of buoys that facilitate the access to wave data. The features
of this network are the optimized cost, high reliability and reduced maintenance.Peer Reviewe
Decays of polarized top quarks to lepton, neutrino and jets at NLO QCD
We compute the differential and total rate of the semileptonic decay of
polarized top-quarks at
next-to-leading order (NLO) in the QCD coupling with an off-shell intermediate
boson. We present several normalized distributions, in particular those
that reflect the -spin analyzing powers of the lepton, the b-jet and the
boson at LO and NLO QCD.Comment: Latex, 22 page
Unimodular Gravity and General Relativity UV divergent contributions to the scattering of massive scalar particles
We work out the one-loop and order UV divergent
contributions, coming from Unimodular Gravity and General Relativity, to the S
matrix element of the scattering process
in a theory with mass . We show that both Unimodular
Gravity and General Relativity give rise to the same UV divergent contributions
in Dimension Regularization. This seems to be at odds with the known result
that in a multiplicative MS dimensional regularization scheme the General
Relativity corrections, in the de Donder gauge, to the beta function
of the coupling do not vanish, whereas the
Unimodular Gravity corrections, in a certain gauge, do vanish. Actually, we
show that the UV divergent contributions to the 1PI Feynman diagrams which give
rise to those non-vanishing corrections to do not contribute
to the UV divergent behaviour of the S matrix element of and this shows that any physical consequence
--such existence of asymptotic freedom due to gravitational interactions--
drawn from the value of is not physically meaningful.Comment: 13 pages, 4 figure
Stable gauged maps
We give an introduction to moduli stacks of gauged maps satisfying a
stability conditition introduced by Mundet and Schmitt, and the associated
integrals giving rise to gauged Gromov-Witten invariants. We survey various
applications to cohomological and K-theoretic Gromov-Witten invariants.Comment: Survey for the 2015 AMS Summer Institute on Algebraic Geometry. Split
off from the more technical paper "Properness for scaled gauged maps"
[arXiv:1606.01383]. There is still substantial overlap between the two
papers. This version has minor correction
Fast-to-Alfv\'en mode conversion mediated by Hall current. II Application to the solar atmosphere
Coupling between fast magneto-acoustic and Alfv\'en waves can be observe in
fully ionized plasmas mediated by stratification and 3D geometrical effects. In
Paper I, Cally & Khomenko (2015) have shown that in a weakly ionized plasma,
such as the solar photosphere and chromosphere, the Hall current introduces a
new coupling mechanism. The present study extends the results from Paper I to
the case of warm plasma. We report on numerical experiments where mode
transformation is studied using quasi-realistic stratification in thermodynamic
parameters resembling the solar atmosphere. This redresses the limitation of
the cold plasma approximation assumed in Paper I, in particular allowing the
complete process of coupling between fast and slow magneto-acoustic modes and
subsequent coupling of the fast mode to the Alfv\'en mode through the Hall
current. Our results confirm the efficacy of the mechanism proposed in Paper I
for the solar case. We observe that the efficiency of the transformation is a
sensitive function of the angle between the wave propagation direction and the
magnetic field, and of the wave frequency. The efficiency increases when the
field direction and the wave direction are aligned for increasing wave
frequencies. After scaling our results to typical solar values, the maximum
amplitude of the transformed Alfv\'en waves, for a frequency of 1 Hz,
corresponds to an energy flux (measured above the height of peak Hall coupling)
of , based on an amplitude of 500 at
, which is sufficient to play a major role in both quiet and active
region coronal heating
Particle collisions near a three-dimensional warped AdS black hole
In this paper we consider the warped AdS black hole solution of
topologically massive gravity with a negative cosmological constant, and we
investigate the possibility that it acts as a particle accelerator by analyzing
the energy in the center of mass (CM) frame of two colliding particles in the
vicinity of its horizon, which is known as the Ba\~nados, Silk and West (BSW)
process. Mainly, we show that the critical angular momentum of the
particle decreases when the parameter that controls the stretching deformation
() increases. Also, we show that despite the particle with can exist
for certain values of the conserved energy outside the horizon, it will never
reach the event horizon; therefore, the black hole can not act as a particle
accelerator with arbitrarily high CM energy on the event horizon. However, such
particle could also exist inside the outer horizon being the BSW process
possible on the inner horizon. On the other hand, for the extremal warped
AdS black hole, the particle with and energy could exist
outside the event horizon and the CM energy blows up on the event horizon if
its conserved energy fulfill the condition
, being the BSW process possible.Comment: 11 pages, 6 figure
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