28,024 research outputs found
Solar Energetic Particle Events in the 23rd Solar Cycle: Interplanetary Magnetic Field Configuration and Statistical Relationship with Flares and CMEs
We study the influence of the large-scale interplanetary magnetic field
configuration on the solar energetic particles (SEPs) as detected at different
satellites near Earth and on the correlation of their peak intensities with the
parent solar activity. We selected SEP events associated with X and M-class
flares at western longitudes, in order to ensure good magnetic connection to
Earth. These events were classified into two categories according to the global
interplanetary magnetic field (IMF) configuration present during the SEP
propagation to 1AU: standard solar wind or interplanetary coronal mass
ejections (ICMEs). Our analysis shows that around 20% of all particle events
are detected when the spacecraft is immersed in an ICME. The correlation of the
peak particle intensity with the projected speed of the SEP-associated coronal
mass ejection is similar in the two IMF categories of proton and electron
events, . The SEP events within ICMEs show stronger correlation
between the peak proton intensity and the soft X-ray flux of the associated
solar flare, with correlation coefficient 0.670.13, compared to the
SEP events propagating in the standard solar wind, 0.360.13. The
difference is more pronounced for near-relativistic electrons. The main reason
for the different correlation behavior seems to be the larger spread of the
flare longitude in the SEP sample detected in the solar wind as compared to SEP
events within ICMEs. We discuss to which extent observational bias, different
physical processes (particle injection, transport, etc.), and the IMF
configuration can influence the relationship between SEPs and coronal activity.Comment: http://adsabs.harvard.edu.ezproxy.obspm.fr/abs/2013SoPh..282..579
A Classical Solution in Six-dimensional Gauge Theory with Higher Derivative Coupling
We show that the spin connection of the standard metric on a six-dimensional
sphere gives an exact solution to the generalized self-dual equations suggested
by Tchrakian some years ago. We work on an SO(6) gauge theory with a
higher-derivative coupling term. The model consists of vector fields only. The
pseudo-energy is bound from below by a topological charge which is proportional
to the winding number of spatial S^5 around the internal space SO(6). The fifth
homotopy group of SO(6) is, indeed, Z. The coupling constant of higher
derivative term is quadratic in the radius of the underlying space S^6.Comment: 7 pages, comments and a reference added, typos correcte
Relaxing Cosmological Constraints on Large Extra Dimensions
We reconsider cosmological constraints on extra dimension theories from the
excess production of Kaluza-Klein gravitons. We point out that, if the normalcy
temperature is above 1 GeV, then graviton states produced at this temperature
will decay early enough that they do not affect the present day dark matter
density, or the diffuse gamma ray background. We rederive the relevant
cosmological constraints for this scenario.Comment: 17 pages, latex, revtex4; added a short discussion of other
constraints, reference
Massive color-octet bosons and the charge asymmetries of top quarks at hadron colliders
Several models predict the existence of heavy colored resonances decaying to
top quarks in the TeV energy range that might be discovered at the LHC. In some
of those models, moreover, a sizable charge asymmetry of top versus antitop
quarks might be generated. The detection of these exotic resonances, however,
requires selecting data samples where the top and the antitop quarks are highly
boosted, which is experimentally very challenging. We asses that the
measurement of the top quark charge asymmetry at the LHC is very sensitive to
the existence of excited states of the gluon with axial-vector couplings to
quarks. We use a toy model with general flavour independent couplings, and show
that a signal can be detected with relatively not too energetic top and antitop
quarks. We also compare the results with the asymmetry predicted by QCD, and
show that its highest statistical significance is achieved with data samples of
top-antitop quark pairs of low invariant masses.Comment: 20 page
Five-Dimensional Unification of the Cosmological Constant and the Photon Mass
Using a non-Riemannian geometry that is adapted to the 4+1 decomposition of
space-time in Kaluza-Klein theory, the translational part of the connection
form is related to the electromagnetic vector potential and a Stueckelberg
scalar. The consideration of a five-dimensional gravitational action functional
that shares the symmetries of the chosen geometry leads to a unification of the
four-dimensional cosmological term and a mass term for the vector potential.Comment: 8 pages, LaTe
Experimental designs for field and semi-field studies with solitary wild bees
The newly proposed EFSA risk assessment of plant protection products for pollinators includes for the first time not only honey bees but also non-Apis pollinators (OEPP/EPPO 2010, EFSA 2013). No official guidelines for standardized tests exist so far. We performed field and semi-field studies to evaluate suitable test designs and handling procedures for the test organisms. The objective of these studies was the development of a test system for trials under field- and semi-field conditions with the red mason bee Osmia bicornis L. (Hymenoptera: Megachilidae). The trials were conducted in two different crops, winter oilseed rape (Brassica napus) and Phacelia (Phacelia tanacetifolia), with different nesting materials, test designs and release techniques
Exact General Relativistic Thick Disks
A method to construct exact general relativistic thick disks that is a simple
generalization of the ``displace, cut and reflect'' method commonly used in
Newtonian, as well as, in Einstein theory of gravitation is presented. This
generalization consists in the addition of a new step in the above mentioned
method. The new method can be pictured as a ``displace, cut, {\it fill} and
reflect'' method. In the Newtonian case, the method is illustrated in some
detail with the Kuzmin-Toomre disk. We obtain a thick disk with acceptable
physical properties. In the relativistic case two solutions of the Weyl
equations, the Weyl gamma metric (also known as Zipoy-Voorhees metric) and the
Chazy-Curzon metric are used to construct thick disks. Also the Schwarzschild
metric in isotropic coordinates is employed to construct another family of
thick disks. In all the considered cases we have non trivial ranges of the
involved parameter that yield thick disks in which all the energy conditions
are satisfied.Comment: 11 pages, RevTex, 9 eps figs. Accepted for publication in PR
Kaluza-Klein Dark Matter
We propose that cold dark matter is made of Kaluza-Klein particles and
explore avenues for its detection. The lightest Kaluza-Klein state is an
excellent dark matter candidate if standard model particles propagate in extra
dimensions and Kaluza-Klein parity is conserved. We consider Kaluza-Klein gauge
bosons. In sharp contrast to the case of supersymmetric dark matter, these
annihilate to hard positrons, neutrinos and photons with unsuppressed rates.
Direct detection signals are also promising. These conclusions are generic to
bosonic dark matter candidates.Comment: 4 pages, 3 figures, discussion of spin-independent cross section
clarified, references added, published versio
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