1,331,496 research outputs found
Structure properties of Th and Fm fission fragments: mean field analysis with the Gogny force
The constrained Hartree-Fock-Bogoliubov method is used with the Gogny
interaction D1S to calculate potential energy surfaces of fissioning nuclei
Th and Fm up to very large deformations. The
constraints employed are the mass quadrupole and octupole moments. In this
subspace of collective coordinates, many scission configurations are identified
ranging from symmetric to highly asymmetric fragmentations. Corresponding
fragment properties at scission are derived yielding fragment deformations,
deformation energies, energy partitioning, neutron binding energies at
scission, neutron multiplicities, charge polarization and total fragment
kinetic energies.Comment: 15 pages, 23 figures, accepted for publication in Phys. Rev. C (2007
A generalization of the Lyndon--Hochschild--Serre spectral sequence with applications to group cohomology and decompositions of groups
We set up a Grothendieck spectral sequence which generalizes the
Lyndon--Hochschild--Serre spectral sequence for a group extension K\mono G\epi
Q by allowing the normal subgroup to be replaced by a subgroup, or family
of subgroups which satisfy a weaker condition than normality. This is applied
to establish a decomposition theorem for certain groups as fundamental groups
of graphs of Poincar\'e duality groups. We further illustrate the method by
proving a cohomological vanishing theorem which applies for example to
Thompson's group .Comment: 22 page
Weakly nonlinear ion sound waves in gravitational systems
Ion sound waves are studied in a plasma subject to gravitational field. Such
systems are interesting by exhibiting a wave growth that is a result of energy
flux conservation in inhomogeneous systems. The increasing wave amplitude gives
rise to an enhanced interaction between waves and plasma particles that can be
modeled by a modified Korteweg-de Vries equation. Analytical results are
compared with numerical Particle-in-Cell simulations of the problem. Our code
assumes isothermally Boltzmann distributed electrons while the ion component is
treated as a collection of individual particles interacting through collective
electric fields. Deviations from quasi neutrality are allowed for.Comment: 30 pages, 9 figure
Zero area singularities in general relativity and inverse mean curvature flow
First we restate the definition of a Zero Area Singularity, recently
introduced by H. Bray. We then consider several definitions of mass for these
singularities. We use the Inverse Mean Curvature Flow to prove some new results
about the mass of a singularity, the ADM mass of the manifold, and the capacity
of the singularity.Comment: 13 page
A closer look at a coronal loop rooted in a sunspot umbra
Extreme UV (EUV) and X-ray loops in the solar corona connect regions of
enhanced magnetic activity, but they are not usually rooted in the dark umbrae
of sunspots because the strong magnetic field found there suppresses
convection. This means that the Poynting flux of magnetic energy into the upper
atmosphere is not significant within the umbra as long as there are no light
bridges or umbral dots. Here we report a rare observation of a coronal loop
rooted in the dark umbra of a sunspot without any traces of light bridges or
umbral dots. We used the slit-jaw images and spectroscopic data from IRIS and
concentrate on the line profiles of O IV and Si IV that show persistent strong
redshifted components in the loop rooted in the umbra. Using the ratios of O
IV, we can estimate the density and thus investigate the mass flux. The coronal
context and temperature diagnostics of these observations is provided through
the EUV channels of AIA. The coronal loop, embedded within cooler downflows,
hosts supersonic downflows. The speed of more than 100 km s is on the
same order of magnitude in the transition region lines of O IV and Si IV, and
is even seen at comparable speed in the chromospheric Mg II lines. At a
projected distance of within of the footpoint, we see a shock transition
to smaller downflow speeds of about 15 km s being consistent with mass
conservation across a stationary isothermal shock. We see no direct evidence
for energy input into the loop because the loop is rooted in the dark uniform
part of the umbra with no light bridges or umbral dots near by. Thus one might
conclude that we are seeing a siphon flow driven from the footpoint at the
other end of the loop. However, for a final result data of similar quality at
the other footpoint are needed, but this is too far away to be covered by the
IRIS field of view.Comment: Accepted for publication in Astronomy and Astrophysics (abridged
abstract
The angular momentum of a magnetically trapped atomic condensate
For an atomic condensate in an axially symmetric magnetic trap, the sum of
the axial components of the orbital angular momentum and the hyperfine spin is
conserved. Inside an Ioffe-Pritchard trap (IPT) whose magnetic field (B-field)
is not axially symmetric, the difference of the two becomes surprisingly
conserved. In this paper we investigate the relationship between the values of
the sum/difference angular momentums for an atomic condensate inside a magnetic
trap and the associated gauge potential induced by the adiabatic approximation.
Our result provides significant new insight into the vorticity of magnetically
trapped atomic quantum gases.Comment: 4 pages, 1 figure
Existence and stability of solitons for the nonlinear Schr\"odinger equation on hyperbolic space
We study the existence and stability of ground state solutions or solitons to
a nonlinear stationary equation on hyperbolic space. The method of
concentration compactness applies and shows that the results correlate strongly
to those of Euclidean space.Comment: New: As noted in Banica-Duyckaerts (arXiv:1411.0846), Section 5
should read that for sufficiently large mass, sub-critical problems can be
solved via energy minimization for all d \geq 2 and as a result
Cazenave-Lions results can be applied in Section 6 with the same restriction.
These requirements were addressed by the subsequent work with Metcalfe and
Taylor in arXiv:1203.361
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