23,923 research outputs found
Continuum time-dependent Hartree-Fock for giant resonances in spherical nuclei
This paper deals with the solution of the spherically symmetric
time-dependent Hartree-Fock approximation applied in the case of nuclear giant
monopole resonances. The problem is spatially unbounded as the resonance state
is in the continuum. The practical requirement to perform the calculation in a
finite-sized spatial region results in a difficulty with the spatial boundary
conditions. Here we propose a absorbing boundary condition scheme to handle the
conflict. The derivation, via a Laplace transform method, and implementation is
described. The accuracy and efficiency of the scheme is tested and the results
presented to support the case that they are a effective way of handling the
artificial boundary.Comment: 13 pages, 8 figure
Morita theory and singularity categories
We propose an analogue of the bounded derived category for an augmented ring
spectrum, defined in terms of a notion of Noether normalization. In many cases
we show this category is independent of the chosen normalization. Based on
this, we define the singularity and cosingularity categories measuring the
failure of regularity and coregularity and prove they are Koszul dual in the
style of the BGG correspondence. Examples of interest include Koszul algebras
and Ginzburg DG-algebras, for finite groups (or for compact Lie
groups with orientable adjoint representation), cochains in rational homotopy
theory and various examples from chromatic homotopy theory.Comment: Final version, accepted for publication in Advances in Mathematics,
49 page
Low-Energy Heavy-Ion Reactions and the Skyrme Effective Interaction
The Skyrme effective interaction, with its multitude of parameterisations,
along with its implemen- tation using the static and time-dependent density
functional (TDHF) formalism have allowed for a range of microscopic
calculations of low-energy heavy-ion collisions. These calculations allow
variation of the effective interaction along with an interpretation of the
results of this variation informed by a comparison to experimental data.
Initial progress in implementing TDHF for heavy-ion collisions necessarily used
many approximations in the geometry or the interaction. Over the last decade or
so, the implementations have overcome all restrictions, and studies have begun
to be made where details of the effective interaction are being probed. This
review surveys these studies in low energy heavy-ion reactions, finding
significant effects on observables from the form of the spin-orbit interaction,
the use of the tensor force, and the inclusion of time-odd terms in the density
functional.Comment: submitted to Prog. Part. Nucl. Phy
Analysis of a Precambrian resonance-stabilized day length
During the Precambrian era, Earth's decelerating rotation would have passed a
21-hour period that would have been resonant with the semidiurnal atmospheric
thermal tide. Near this point, the atmospheric torque would have been
maximized, being comparable in magnitude but opposite in direction to the lunar
torque, halting Earth's rotational deceleration, maintaining a constant day
length, as detailed by Zahnle and Walker (1987). We develop a computational
model to determine necessary conditions for formation and breakage of this
resonant effect. Our simulations show the resonance to be resilient to
atmospheric thermal noise but suggest a sudden atmospheric temperature increase
like the deglaciation period following a possible "snowball Earth" near the end
of the Precambrian would break this resonance; the Marinoan and Sturtian
glaciations seem the most likely candidates for this event. Our model provides
a simulated day length over time that resembles existing paleorotational data,
though further data is needed to verify this hypothesis.Comment: 7 pages, 5 figures. Accepted for publication in Geophysical Research
Letters on 10 May 201
A semi-implicit numerical method for treating the time transient gas lubrication equation
Numerical method for treating time transient gas lubrication equatio
Rural land mobile radio market assessment and satellite and terrestrial system concepts
Market potential exists; the nature of the market in terms of service needs, usage characteristics, service requirements, and forecasting the demand to the year 2000; alternative system cncepts that show promise in addressing the identified needs, in a cost effective manner; and advanced technology requirements associated with these concepts are considered
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