16,758 research outputs found
Tracking in Antiproton Annihilation Experiments
A major ingredient of the planned new accelerator complex FAIR, to be
constructed at the GSI, Darmstadt, Germany, is the availability of antiproton
beams with high quality and intensity. Among the experiments which will make
use of this opportunity is PANDA, a dedicated experiment to study antiproton
annihilations on nucleons and nuclei. This article gives an overview on the
foreseen techniques to perform charged particle tracking in the high rate
environment of this experiment.Comment: 1 tar.gz file containing 5 pages paper, 3 figures in 5 files;
proceedings of the TIME05 worksho
Typical and large-deviation properties of minimum-energy paths on disordered hierarchical lattices
We perform numerical simulations to study the optimal path problem on
disordered hierarchical graphs with effective dimension d=2.32. Therein, edge
energies are drawn from a disorder distribution that allows for positive and
negative energies. This induces a behavior which is fundamentally different
from the case where all energies are positive, only. Upon changing the
subtleties of the distribution, the scaling of the minimum energy path length
exhibits a transition from self-affine to self-similar. We analyze the precise
scaling of the path length and the associated ground-state energy fluctuations
in the vincinity of the disorder critical point, using a decimation procedure
for huge graphs. Further, using an importance sampling procedure in the
disorder we compute the negative-energy tails of the ground-state energy
distribution up to 12 standard deviations away from its mean. We find that the
asymptotic behavior of the negative-energy tail is in agreement with a
Tracy-Widom distribution. Further, the characteristic scaling of the tail can
be related to the ground-state energy flucutations, similar as for the directed
polymer in a random medium.Comment: 10 pages, 10 figures, 3 table
Configurational statistics of densely and fully packed loops in the negative-weight percolation model
By means of numerical simulations we investigate the configurational
properties of densely and fully packed configurations of loops in the
negative-weight percolation (NWP) model. In the presented study we consider 2d
square, 2d honeycomb, 3d simple cubic and 4d hypercubic lattice graphs, where
edge weights are drawn from a Gaussian distribution. For a given realization of
the disorder we then compute a configuration of loops, such that the
configurational energy, given by the sum of all individual loop weights, is
minimized. For this purpose, we employ a mapping of the NWP model to the
"minimum-weight perfect matching problem" that can be solved exactly by using
sophisticated polynomial-time matching algorithms. We characterize the loops
via observables similar to those used in percolation studies and perform
finite-size scaling analyses, up to side length L=256 in 2d, L=48 in 3d and
L=20 in 4d (for which we study only some observables), in order to estimate
geometric exponents that characterize the configurations of densely and fully
packed loops. One major result is that the loops behave like uncorrelated
random walks from dimension d=3 on, in contrast to the previously studied
behavior at the percolation threshold, where random-walk behavior is obtained
for d>=6.Comment: 11 pages, 7 figure
Gaussian quantum fluctuations in interacting many particle systems
We consider a many particle quantum system, in which each particle interacts
only with its nearest neighbours. Provided that the energy per particle has an
upper bound, we show, that the energy distribution of almost every product
state becomes a Gaussian normal distribution in the limit of infinite number of
particles. We indicate some possible applications.Comment: 10 pages, formulation made mathematically more precise, two examples
added, accepted for publication in Letters in Mathematical Physic
The new Mars: The discoveries of Mariner 9
The Mariner 9 encounter with Mars is extensively documented with photographs taken by the satellite's onboard cameras, and an attempt is made to explain the observed Martian topography in terms of what is known about the geomorphological evolution of the earth. Early conceptions about the Mars surface are compared with more recent data made available by the Mariner 9 cameras. Other features of the planet Mars which are specifically discussed include the volcanic regions, the surface channels, the polar caps and layered terrain, the Martian atmosphere, and the planet's two moons--Phobos and Deimos
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