6,588 research outputs found
Why we need to see the dark matter to understand the dark energy
The cosmological concordance model contains two separate constituents which
interact only gravitationally with themselves and everything else, the dark
matter and the dark energy. In the standard dark energy models, the dark matter
makes up some 20% of the total energy budget today, while the dark energy is
responsible for about 75%. Here we show that these numbers are only robust for
specific dark energy models and that in general we cannot measure the abundance
of the dark constituents separately without making strong assumptions.Comment: 4 pages, to be published in the Journal of Physics: Conference Series
as a contribution to the 2007 Europhysics Conference on High Energy Physic
Control of apple scab by curative applications of biocontrol agents
In organic apple growing protective applications with copper, sulphur or lime sulphur are
used for apple scab control. Protective applications have to be repeated when new leaves
unfold. The timing of protective sprays depends on the weather forecast. If forecasted
infection conditions fail to appear, treatments were for nothing. With curative control
agents available, the number of treatments could be reduced. In greenhouse trials we
tested control agents for their protective and curative efficiency against apple scab after
artificial inoculation of potted apple trees. Applications were done 2 hours before
inoculation, 5 hours after inoculation on wet leaves, 5 hours after inoculation during
simulated rainfall or 24 hours after inoculation on wet or dry leaves. The optimal time of
application differed between the preparations tested. Vitisan and OmniProtect had their
highest activity when sprayed curative 24 hours after inoculation. Combinations were
found, which revealed a high efficiency against apple scab from 2h before to 24 hours after
inoculation. In a field trial apple scab was effectively controlled by curative applications of
OmniProtect
On Axially Symmetric Solutions in the Electroweak Theory
We present the general ansatz, the energy density and the Chern-Simons charge
for static axially symmetric configurations in the bosonic sector of the
electroweak theory. Containing the sphaleron, the multisphalerons and the
sphaleron-antisphaleron pair at finite mixing angle, the ansatz further allows
the construction of the sphaleron and multisphaleron barriers and of the
bisphalerons at finite mixing angle. We conjecture that further solutions
exist.Comment: 17 pages, latex, THU-94/0
D=5 Einstein-Maxwell-Chern-Simons Black Holes
5-dimensional Einstein-Maxwell-Chern-Simons theory with Chern-Simons
coefficient has supersymmetric black holes with vanishing horizon
angular velocity, but finite angular momentum. Here supersymmetry is associated
with a borderline between stability and instability, since for a
rotational instability arises, where counterrotating black holes appear, whose
horizon rotates in the opposite sense to the angular momentum. For
black holes are no longer uniquely characterized by their global charges, and
rotating black holes with vanishing angular momentum appear.Comment: 4 pages, 4 figures, RevTeX styl
Level Crossing Along Sphaleron Barriers
In the electroweak sector of the standard model topologically inequivalent
vacua are separated by finite energy barriers, whose height is given by the
sphale\-ron. For large values of the Higgs mass there exist several sphaleron
solutions and the barriers are no longer symmetric. We construct paths of
classical configurations from one vacuum to a neighbouring one and solve the
fermion equations in the background field configurations along such paths,
choosing the fermions of a doublet degenerate in mass. As in the case of light
Higgs masses we observe the level crossing phenomenon also for large Higgs
masses.Comment: 17 pages, latex, 10 figures in uuencoded postscript files. THU-94/0
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