76,662 research outputs found
Space-charge compensation experiments at IOTA ring
Space-charge effects belong to the category of the most long-standing issues
in beam physics, and even today, after several decades of very active
exploration and development of counter-measures, they still pose the most
profound limitations on performance of high intensity proton accelerators. We
briefly consider past experience in active compensation of these effects and
present in detail the progress towards experimental studies of novel schemes of
space-charge compensation at the Fermilab's IOTA ring.Comment: 5 p
Discovery of Counter-Rotating Gas in the Galaxies NGC1596 and NGC3203 and the Incidence of Gas Counter-Rotation in S0 Galaxies
We have identified two new galaxies with gas counter-rotation (NGC1596 and
NGC3203) and have confirmed similar behaviour in another one (NGC128), this
using results from separate studies of the ionized-gas and stellar kinematics
of a well-defined sample of 30 edge-on disc galaxies. Gas counter-rotators thus
represent 10+/-5% of our sample, but the fraction climbs to 21+/-11% when only
lenticular (S0) galaxies are considered and to 27+/-13% for S0s with detected
ionized-gas only. Those fractions are consistent with but slightly higher than
previous studies. A compilation from well-defined studies of S0s in the
literature yields fractions of 15+/-4% and 23+/-5%, respectively. Although
mainly based on circumstantial evidence, we argue that the counter-rotating gas
originates primarily from minor mergers and tidally-induced transfer of
material from nearby objects. Assuming isotropic accretion, twice those
fractions of objects must have undergone similar processes, underlining the
importance of (minor) accretion for galaxy evolution. Applications of gas
counter-rotators to barred galaxy dynamics are also discussed.Comment: 8 pages, including 1 table and 2 figures. Accepted for publication in
MNRAS. Version with full resolution figures available at
http://www-astro.physics.ox.ac.uk/~bureau/pub_list.htm
A unified approach to compute foliations, inertial manifolds, and tracking initial conditions
Several algorithms are presented for the accurate computation of the leaves
in the foliation of an ODE near a hyperbolic fixed point. They are variations
of a contraction mapping method in [25] to compute inertial manifolds, which
represents a particular leaf in the unstable foliation. Such a mapping is
combined with one for the leaf in the stable foliation to compute the tracking
initial condition for a given solution. The algorithms are demonstrated on the
Kuramoto-Sivashinsky equation
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