5,904 research outputs found
Exploring Thermal Processing of the Mildly Aqueously Altered Cm2 Eet 96029 Using Sulphide Mineralogy and Carbon Structure [abstract]
No abstract available
The magnetic form factor of the deuteron in chiral effective field theory
We calculate the magnetic form factor of the deuteron up to O(eP^4) in the
chiral EFT expansion of the electromagnetic current operator. The two LECs
which enter the two-body part of the isoscalar NN three-current operator are
fit to experimental data, and the resulting values are of natural size. The
O(eP^4) description of G_M agrees with data for momentum transfers Q^2 < 0.35
GeV^2.Comment: 4 pages, 2 figure
Fock space relativistic coupled-Cluster calculations of Two-Valence Atoms
We have developed an all particle Fock-space relativistic coupled-cluster
method for two-valence atomic systems. We then describe a scheme to employ the
coupled-cluster wave function to calculate atomic properties. Based on these
developments we calculate the excitation energies, magnetic hyperfine constants
and electric dipole matrix elements of Sr, Ba and Yb. Further more, we
calculate the electric quadrupole HFS constants and the electric dipole matrix
elements of Sr, Ba and Yb. For these we use the one-valence
coupled-cluster wave functions obtained as an intermediate in the two-valence
calculations. We also calculate the magnetic dipole hyperfine constants of
Yb.Comment: 23 pages, 12 figures, 10 tables typos are corrected and some minor
modifications in some of the section
A streamwise-constant model of turbulent pipe flow
A streamwise-constant model is presented to investigate the basic mechanisms
responsible for the change in mean flow occuring during pipe flow transition.
Using a single forced momentum balance equation, we show that the shape of the
velocity profile is robust to changes in the forcing profile and that both
linear non-normal and nonlinear effects are required to capture the change in
mean flow associated with transition to turbulence. The particularly simple
form of the model allows for the study of the momentum transfer directly by
inspection of the equations. The distribution of the high- and low-speed
streaks over the cross-section of the pipe produced by our model is remarkably
similar to one observed in the velocity field near the trailing edge of the
puff structures present in pipe flow transition. Under stochastic forcing, the
model exhibits a quasi-periodic self-sustaining cycle characterized by the
creation and subsequent decay of "streamwise-constant puffs", so-called due to
the good agreement between the temporal evolution of their velocity field and
the projection of the velocity field associated with three-dimensional puffs in
a frame of reference moving at the bulk velocity. We establish that the flow
dynamics are relatively insensitive to the regeneration mechanisms invoked to
produce near-wall streamwise vortices and that using small, unstructured
background disturbances to regenerate the streamwise vortices is sufficient to
capture the formation of the high- and low-speed streaks and their segregation
leading to the blunting of the velocity profile characteristic of turbulent
pipe flow
Novel self-assembled morphologies from isotropic interactions
We present results from particle simulations with isotropic medium range
interactions in two dimensions. At low temperature novel types of aggregated
structures appear. We show that these structures can be explained by
spontaneous symmetry breaking in analytic solutions to an adaptation of the
spherical spin model. We predict the critical particle number where the
symmetry breaking occurs and show that the resulting phase diagram agrees well
with results from particle simulations.Comment: 4 pages, 4 figure
Using the uncertainty principle to design simple interactions for targeted self-assembly
We present a method that systematically simplifies isotropic interactions designed for targeted self-assembly. The uncertainty principle is used to show that an optimal simplification is achieved by a combination of heat kernel smoothing and Gaussian screening of the interaction potential in real and reciprocal space. We use this method to analytically design isotropic interactions for self-assembly of complex lattices and of materials with functional properties. The derived interactions are simple enough to narrow the gap between theory and experimental implementation of theory based designed self-assembling materials
Relativistic coupled-cluster calculations of Ne, Ar, Kr and Xe: correlation energies and dipole polarizabilities
We have carried out a detailed and systematic study of the correlation
energies of inert gas atoms Ne, Ar, Kr and Xe using relativistic many-body
perturbation theory and relativistic coupled-cluster theory. In the
relativistic coupled-cluster calculations, we implement perturbative triples
and include these in the correlation energy calculations. We then calculate the
dipole polarizability of the ground states using perturbed coupled-cluster
theory.Comment: 10 figures, 6 tables, submitted to PR
Seen and unseen tidal caustics in the Andromeda galaxy
Indirect detection of high-energy particles from dark matter interactions is
a promising avenue for learning more about dark matter, but is hampered by the
frequent coincidence of high-energy astrophysical sources of such particles
with putative high-density regions of dark matter. We calculate the boost
factor and gamma-ray flux from dark matter associated with two shell-like
caustics of luminous tidal debris recently discovered around the Andromeda
galaxy, under the assumption that dark matter is its own supersymmetric
antiparticle. These shell features could be a good candidate for indirect
detection of dark matter via gamma rays because they are located far from the
primary confusion sources at the galaxy's center, and because the shapes of the
shells indicate that most of the mass has piled up near apocenter. Using a
numerical estimator specifically calibrated to estimate densities in N-body
representations with sharp features and a previously determined N-body model of
the shells, we find that the largest boost factors do occur in the shells but
are only a few percent. We also find that the gamma-ray flux is an order of
magnitude too low to be detected with Fermi for likely dark matter parameters,
and about 2 orders of magnitude less than the signal that would have come from
the dwarf galaxy that produces the shells in the N-body model. We further show
that the radial density profiles and relative radial spacing of the shells, in
either dark or luminous matter, is relatively insensitive to the details of the
potential of the host galaxy but depends in a predictable way on the velocity
dispersion of the progenitor galaxy.Comment: ApJ accepte
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