96 research outputs found
Future non-linear stability of the Einstein-Vlasov system with reflection Bianchi II and VI0 symmetry
Assuming that the space-time is close to special solutions which will play the role of the ω-limit and that the maximal velocity of the particles is small, we have been able to show that for reflection symmetric Bianchi II and reflection symmetric Bianchi VI0 spacetimes with collisionless matter the asymptotic behaviour at late times is close to the special case of dust. The key was a bootstrap argument
Late-time behaviour of the Einstein-Vlasov system with Bianchi I symmetry
The late-time behaviour of the Einstein-dust system is well understood for homogeneous spacetimes. For the case of Bianchi I we have been able to show that the late-time behaviour of the Einstein-Vlasov system is well approximated by the Einstein-dust system assuming that one is close to the unique stationary solution which is the attractor of the Einstein-dust system
Late-time behaviour of the Einstein-Vlasov system with Bianchi I symmetry
The late-time behaviour of the Einstein-dust system is well understood for
homogeneous spacetimes. For the case of Bianchi I we have been able to show
that the late-time behaviour of the Einstein-Vlasov system is well approximated
by the Einstein-dust system assuming that one is close to the unique stationary
solution which is the attractor of the Einstein-dust system.Comment: 4 pages, based on a talk given at the Spanish Relativity Meeting
2010, to appear in Journal of Physics: Conference Series (JPCS
Late-time behaviour of the Einstein-Vlasov system with Bianchi I symmetry
The late-time behaviour of the Einstein-dust system is well understood for
homogeneous spacetimes. For the case of Bianchi I we have been able to show
that the late-time behaviour of the Einstein-Vlasov system is well approximated
by the Einstein-dust system assuming that one is close to the unique stationary
solution which is the attractor of the Einstein-dust system.Comment: 4 pages, based on a talk given at the Spanish Relativity Meeting
2010, to appear in Journal of Physics: Conference Series (JPCS
Late-time behaviour of the Einstein-Vlasov system with Bianchi I symmetry
The late-time behaviour of the Einstein-dust system is well understood for
homogeneous spacetimes. For the case of Bianchi I we have been able to show
that the late-time behaviour of the Einstein-Vlasov system is well approximated
by the Einstein-dust system assuming that one is close to the unique stationary
solution which is the attractor of the Einstein-dust system.Comment: 4 pages, based on a talk given at the Spanish Relativity Meeting
2010, to appear in Journal of Physics: Conference Series (JPCS
Future non-linear stability for reflection symmetric solutions of the Einstein-Vlasov system of Bianchi types II and VI
Using the methods developed for the Bianchi I case we have shown that a
boostrap argument is also suitable to treat the future non-linear stability for
reflection symmetric solutions of the Einstein-Vlasov system of Bianchi types
II and VI. These solutions are asymptotic to the Collins-Stewart solution
with dust and the Ellis-MacCallum solution respectively. We have thus
generalized the results obtained by Rendall and Uggla in the case of locally
rotationally symmetric Bianchi II spacetimes to the reflection symmetric case.
However we needed to assume small data. For Bianchi VI there is no
analogous previous result.Comment: 30 page
Strong cosmic censorship for solutions of the Einstein-Maxwell field equations with polarized Gowdy symmetry
A proof of strong cosmic censorship is presented for a class of solutions of
the Einstein-Maxwell equations, those with polarized Gowdy symmetry. A key
element of the argument is the observation that by means of a suitable choice
of variables the central equations in this problem can be written in a form
where they are identical to the central equations for general (i.e.
non-polarized) vacuum Gowdy spacetimes. Using this it is seen that the deep
results of Ringstr\"om on strong cosmic censorship in the vacuum case have
implications for the Einstein-Maxwell case. Working out the geometrical meaning
of these analytical results leads to the main conclusion.Comment: Some references have been change
Measurement of Strange Quark Contributions to the Nucleon's Form Factors at Q^2=0.230 (GeV/c)^2
We report on a measurement of the parity-violating asymmetry in the
scattering of longitudinally polarized electrons on unpolarized protons at a
of 0.230 (GeV/c)^2 and a scattering angle of \theta_e = 30^o - 40^o.
Using a large acceptance fast PbF_2 calorimeter with a solid angle of
\Delta\Omega = 0.62 sr the A4 experiment is the first parity violation
experiment to count individual scattering events. The measured asymmetry is
A_{phys} =(-5.44 +- 0.54_{stat} +- 0.27_{\rm sys}) 10^{-6}. The Standard Model
expectation assuming no strangeness contributions to the vector form factors is
. The difference is a direct measurement of the
strangeness contribution to the vector form factors of the proton. The
extracted value is G^s_E + 0.225 G^s_M = 0.039 +- 0.034 or F^s_1 + 0.130 F^s_2
= 0.032 +- 0.028.Comment: 5 pages, 3 figures, submitted to Phys. Rev. Letters on Dec 11, 200
New detectors for the kaon and hypernuclear experiments with KaoS at MAMI and with PANDA at GSI
The KaoS spectrometer at the Mainz Microtron MAMI, Germany, is perceived as
the ideal candidate for a dedicated spectrometer in kaon and hypernuclei
electroproduction. KaoS will be equipped with new read-out electronics, a
completely new focal plane detector package consisting of scintillating fibres,
and a new trigger system. First prototypes of the fibre detectors and the
associated new front-end electronics are shown in this contribution. The Mainz
hypernuclei research program will complement the hypernuclear experiments at
the planned FAIR facility at GSI, Germany. At the proposed antiproton storage
ring the spectroscopy of double Lambda hypernuclei is one of the four main
topics which will be addressed by the PANDA Collaboration. The experiments
require the operation of high purity germanium (HPGe) detectors in high
magnetic fields (B= 1T) in the presence of a large hadronic background. The
performance of high resolution Ge detectors in such an environment has been
investigated.Comment: Presentation at International Symposium on the Development of
Detectors for Particle, Astroparticle and Synchrotron Radiation Experiments,
Stanford, Ca (SNIC06), 6 pages, LaTeX, 11 eps figure
Exclusive electroproduction of K+ Lambda and K+ Sigma^0 final states at Q^2 = 0.030-0.055 (GeV/c)^2
Cross section measurements of the exclusive p(e,e'K+)Lambda,Sigma^0
electroproduction reactions have been performed at the Mainz Microtron MAMI in
the A1 spectrometer facility using for the first time the Kaos spectrometer for
kaon detection. These processes were studied in a kinematical region not
covered by any previous experiment. The nucleon was probed in its third
resonance region with virtual photons of low four-momenta, Q^2= 0.030-0.055
(GeV/c)^2. The MAMI data indicate a smooth transition in Q^2 from
photoproduction to electroproduction cross sections. Comparison with
predictions of effective Lagrangian models based on the isobar approach reveal
that strong longitudinal couplings of the virtual photon to the N* resonances
can be excluded from these models.Comment: 16 pages, 7 figure
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