2,838 research outputs found
Production of non-Abelian tensor gauge bosons. Tree amplitudes in generalized Yang-Mills theory and BCFW recursion relation
The BCFW recursion relation allows to calculate tree-level scattering
amplitudes in generalized Yang-Mills theory and, in particular, four-particle
amplitudes for the production rate of non-Abelian tensor gauge bosons of
arbitrary high spin in the fusion of two gluons. The consistency of the
calculations in different kinematical channels is fulfilled when all
dimensionless cubic coupling constants between vector bosons (gluons) and high
spin non-Abelian tensor gauge bosons are equal to the Yang-Mills coupling
constant. There are no high derivative cubic vertices in the generalized
Yang-Mills theory. The amplitudes vanish as complex deformation parameter tends
to infinity, so that there is no contribution from the contour at infinity. We
derive a generalization of the Parke-Taylor formula in the case of production
of two tensor gauge bosons of spin-s and N gluons (jets). The expression is
holomorhic in the spinor variables of the scattered particles, exactly as the
MHV gluon amplitude is, and reduces to the gluonic MHV amplitude when s=1. In
generalized Yang-Mills theory the tree level n-particle scattering amplitudes
with all positive helicities vanish, but tree amplitudes with one negative
helicity particle are already nonzero.Comment: 19 pages, LaTex fil
Variational Data Assimilation via Sparse Regularization
This paper studies the role of sparse regularization in a properly chosen
basis for variational data assimilation (VDA) problems. Specifically, it
focuses on data assimilation of noisy and down-sampled observations while the
state variable of interest exhibits sparsity in the real or transformed domain.
We show that in the presence of sparsity, the -norm regularization
produces more accurate and stable solutions than the classic data assimilation
methods. To motivate further developments of the proposed methodology,
assimilation experiments are conducted in the wavelet and spectral domain using
the linear advection-diffusion equation
A new type of lordosis and vertebral body compression in Gilthead seabream, Sparus aurata Linnaeus, 1758: aetiology, anatomy and consequences for survival
A new type of vertebral malformation is described, consisting of deformed cartilaginous neural and haemal processes and the compression and fusion of vertebral bodies. The malformation is designated as haemal vertebral compression and fusion (haemal VCF). We studied the aetiology of the malformations and described microanatomical histopathological alterations. The malformations were detected during routine quality control in one of six monitored Gilthead sea bream populations. Haemal VCF affected the posterior part of the vertebral column (haemal vertebrae). In 20% of the deformed specimens, haemal VCF was combined with lordosis. At 35dph (days post-hatching), early anatomical signs of the haemal VCF consisted of abnormal centrum mineralization, malformed cartilaginous neural and haemal processes and developing lordotic alterations. The histological examination of the deformed individuals revealed that haemal VCF is preceded by notochord abnormalities. The frequency of deformed individuals was three times higher at 35 than at 61dph (50.3% vs. 17.2%, n=157 and n=250, respectively). No signs of repair or reversion of malformations have been observed. Thus, the steep decrease in deformities in older animals suggests that haemal VCF is linked to high mortality rates. The results are discussed in respect of the possible causative factors of haemal VCF
A Study of Halo Coronal Mass Ejections and Related Flare and Radio Burst Observations in Solar Cycle 23
We present a statistical study of dynamical and kinetic characteristics of
CMEs which show temporal and spatial association with flares and type II radio
bursts or complex radio events of type II bursts and type IV continua. This
study is based on a set of earth-directed full halo CMEs occurring during the
present solar cycle, with data from the Large Angle Spectrometric Coronagraphs
(LASCO) and Extreme-Ultraviolet Imaging Telescope (EIT) aboard the Solar and
Heliospheric Observatory (SOHO) mission and the Magnetic Fields Investigation
(MFI) and 3-D Plasma and Energetic Particle Analyzer Investigation experiment
on board the WIND spacecraft.Comment: Recent Advances in Astronomy and Astrophysics: 7th International
Conference of the Hellenic Astronomical Society. AIP Conference Proceedings,
Volume 848, pp. 218-223 (2006
Six-Quark Amplitudes from Fermionic MHV Vertices
The fermionic extension of the CSW approach to perturbative gauge theory
coupled with fermions is used to compute the six-quark QCD amplitudes. We find
complete agreement with the results obtained by using the usual Feynman rules.Comment: Latex file, 16 pages, 4 figure
Application of liquid-air and pumped-thermal electricity storage systems in low-carbon electricity systems
In this study, w e consider two medium - to large - scale electricity storage systems currently under development, namely ‘Liquid - Air Energy Storage’ (LAES) and ‘Pumped - Therma l Electricity Storage’ (PTES). Consistent t hermodynamic models and costing methodologies for the two systems are presented , with the object ive of integrating the characteristics of these technologies in to a whole - electricity system assessment model , and assess ing the ir system - level value in different scenarios for power system decarbonisation . It is found that the value of storage varies greatly depending on the cumulative installed ca pacity of storage in the electrical system, with the s torage technologies provid ing greater marginal benefits at low p enetrations . T wo carbon target scenarios showed similar results, with a limited effect of the carbon target on the system value of storage (although it is noted that this may change for even more ambitious carbon targets). On the other hand, the location and installed capacity of storage plants is found to have a significant impact on the syste m value and acceptable cost of the se technologies. The w hole - system value of PTES was found to be slightly higher than that of LAES, driven by a higher storage duration and efficiency, however, due to the higher power capital cost of PTES, this becomes les s attractive for implementat ion at lower volumes than LAES
Influence of boundary conditions on quantum escape
It has recently been established that quantum statistics can play a crucial
role in quantum escape. Here we demonstrate that boundary conditions can be
equally important - moreover, in certain cases, may lead to a complete
suppression of the escape. Our results are exact and hold for arbitrarily many
particles.Comment: 6 pages, 3 figures, 1 tabl
Association of radiation belt electron enhancements with earthward penetration of Pc5 ULF waves: a case study of intense 2001 magnetic storms
Geospace magnetic storms, driven by the solar
wind, are associated with increases or decreases in the fluxes
of relativistic electrons in the outer radiation belt. We examine
the response of relativistic electrons to four intense
magnetic storms, during which the minimum of the Dst index
ranged from −105 to −387 nT, and compare these with
concurrent observations of ultra-low-frequency (ULF) waves
from the trans-Scandinavian IMAGE magnetometer network
and stations from multiple magnetometer arrays available
through the worldwide SuperMAG collaboration. The latitudinal
and global distribution of Pc5 wave power is examined
to determine how deep into the magnetosphere these
waves penetrate. We then investigate the role of Pc5 wave
activity deep in the magnetosphere in enhancements of radiation
belt electrons population observed in the recovery
phase of the magnetic storms. We show that, during magnetic
storms characterized by increased post-storm electron fluxes
as compared to their pre-storm values, the earthward shift of
peak and inner boundary of the outer electron radiation belt
follows the Pc5 wave activity, reaching L shells as low as
3–4. In contrast, the one magnetic storm characterized by irreversible
loss of electrons was related to limited Pc5 wave
activity that was not intensified at low L shells. These observations
demonstrate that enhanced Pc5 ULF wave activity
penetrating deep into the magnetosphere during the main and
recovery phase of magnetic storms can, for the cases examined,
distinguish storms that resulted in increases in relativistic
electron fluxes in the outer radiation belts from those that
did not
Wang-Landau study of the random bond square Ising model with nearest- and next-nearest-neighbor interactions
We report results of a Wang-Landau study of the random bond square Ising
model with nearest- () and next-nearest-neighbor ()
antiferromagnetic interactions. We consider the case for
which the competitive nature of interactions produces a sublattice ordering
known as superantiferromagnetism and the pure system undergoes a second-order
transition with a positive specific heat exponent . For a particular
disorder strength we study the effects of bond randomness and we find that,
while the critical exponents of the correlation length , magnetization
, and magnetic susceptibility increase when compared to the
pure model, the ratios and remain unchanged. Thus, the
disordered system obeys weak universality and hyperscaling similarly to other
two-dimensional disordered systems. However, the specific heat exhibits an
unusually strong saturating behavior which distinguishes the present case of
competing interactions from other two-dimensional random bond systems studied
previously.Comment: 9 pages, 3 figures, version as accepted for publicatio
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