6358551
The formation of black holes in spherically symmetric gravitational collapse
We consider the spherically symmetric, asymptotically flat Einstein–Vlasov system. We find explicit conditions on the initial data, with ADM mass M, such that the resulting spacetime has the following properties: there is a family of radially outgoing null geodesics where the area radius r along each geodesic is bounded by 2M, the timelike lines $${r=c\in [0,2M]}$$ are incomplete, and for r > 2M the metric converges asymptotically to the Schwarzschild metric with mass M. The initial data that we construct guarantee the formation of a black hole in the evolution. We give examples of such initial data with the additional property that the solutions exist for all r ≥ 0 and all Schwarzschild time, i.e., we obtain global existence in Schwarzschild coordinates in situations where the initial data are not small. Some of our results are also established for the Einstein equations coupled to a general matter model characterized by conditions on the matter quantities.
53967767
Existence of Axially Symmetric Static Solutions of the Einstein-Vlasov System
We prove the existence of static, asymptotically flat non-vacuum spacetimes with axial symmetry where the matter is modeled as a collisionless gas. The axially symmetric solutions of the resulting Einstein-Vlasov system are obtained via the implicit function theorem by perturbing off a suitable spherically symmetric steady state of the Vlasov-Poisson system.
6557807
Global Existence for the Spherically Symmetric Einstein–Vlasov System with Outgoing Matter
We prove a new global existence result for the asymptotically flat, spherically symmetric Einstein–Vlasov system which describes in the framework of general relativity an ensemble of particles which interact by gravity. The data are such that initially all the particles are moving radially outward and that this property can be bootstrapped. The resulting non-vacuum spacetime is future geodesically complete.
16238417
Gravitational collapse and the formation of black holes for the spherically symmetric Einstein-Vlasov system
We review results on the spherically symmetric, asymptotically flat Einstein-Vlasov system. We focus on a recent result where we found explicit conditions on the initial data which guarantee the formation of a black hole in the evolution. Among these data there are data such that the corresponding solutions exist globally in Schwarzschild coordinates. We put these results into a more general context, and we include arguments which show that the spacetimes we obtain satisfy the weak cosmic censorship conjecture and contain a black hole in the sense of suitable mathematical definitions of these concepts which are available in the literature.
123368629
Annihilation at rest of antiprotons and protons into neutral particles
Abstract Annihilation of antiprotons and protons at rest into neutral particles has been studied with the Crystal Barrel detector at LEAR. Annihilation frequencies are determined for final states containing π 0 , η , η ′ and ω mesons using a liquid and a room temperature, 12 bar, gaseous hydrogen target. Including annihilation frequencies for production of neutral kaons from other experiments, the identified reactions for annihilation in liquid hydrogen add up to a branching fraction of (3.56±0.28)% per annihilation compared to the frequency of (3.50±0.30)% with which we observe the all-neutral decay modes inclusively. Since the exclusive final states are normalized to the Crystal Barrel measurement of the π 0 π 0 branching ratio, the latter result is strongly supported by this present study.
1655743
A distributed, Grid-based analysis system for the MAGIC telescope
The observation of high-energetic γ-rays with ground based air cerenkov telescopes is one of the most exciting areas in modern astro particle physics giving insight into active galactic nuclei (AGN), pulsars, supernova remnants, unidentified EGRET sources, γ-ray bursts and cosmology. The MAGIC telescope started operation at the end of 2003. The low energy threshold for γ-rays together with different background sources leads to a considerable amount of data. The data analysis will be done in different institutes spread across Europe. The production of Monte Carlo events including the simulation of Cerenkov light in the atmosphere is very computing intensive and another challenge for a collaboration like MAGIC. The current Grid technology widely deployed over 80 sites by LCG has recently proven to be mature and well adapted to set up a distributed computational and data intensive analysis system meeting the requirements of experiments like MAGIC. The basic architecture of such a distributed, Europe wide Grid system will be presented. First implementation results will be shown. This Grid might be the starting point for a wider distributed astro particle Grid in Europe.
12991826
A comparison between the performance of feed forward neural networks and the supervised growing neural gas algorithm
Abstract The Supervised Growing Neural Gas algorithm (SGNG) provides an interesting alternative to standard Multi-Layer Perceptrons (MLP). A comparison is drawn between the performance of SGNG and MLP in the domain of function mapping. A further field of interest is classification power, which has been investigated with real data taken by PS197 at CERN. The characteristics of the two network models will be discussed from a practical point of view as well as their advantages and disadvantages.
122322573
New states as observed by the Crystal Barrel experiment
Abstract The Crystal Barrel Detector has been in operation since October 1989. Results on the analysis of the annihilation of protonium at rest into three pseudoscalars is presented. The π 0 π 0 π 0 final state confirms the existence of ƒ 2 (1520)→π 0 π 0 . In the ηη system of the π 0 ηη final state an isoscalar J PC = 0 ++ resonance with a mass of 1560 MeV/c 2 and a width of 245 MeV/c 2 is observed. The identification with ƒ 0 (1590) is doubtful since the ηη' decay is not observed with the corresponding strength. Our analysis yields an upper limit for the relative branching ratio BR(ƒ 0 (1560)→ηη') BR(ƒ 0 (1560)→ηη) .
121889238
Antiproton-proton annihilation at rest into two mesons
Abstract Branching ratios for antiproton-proton annihilations at rest into two mesons are given. The data were obtained at LEAR by stopping antiprotons in a liquid hydrogen target. Both charged and neutral annihilation products were detected in the Crystal Barrel detector. Representative data are presented, and their bearing on the general picture of annihilation dynamics is discussed. In addition, preliminary branching ratios for two-body radiative annihilations are given.