729 research outputs found
Coordinate-Space Hartree-Fock-Bogoliubov Solvers for Superfluid Fermi Systems in Large Boxes
The self-consistent Hartree-Fock-Bogoliubov problem in large boxes can be
solved accurately in the coordinate space with the recently developed solvers
HFB-AX (2D) and MADNESS-HFB (3D). This is essential for the description of
superfluid Fermi systems with complicated topologies and significant spatial
extend, such as fissioning nuclei, weakly-bound nuclei, nuclear matter in the
neutron star rust, and ultracold Fermi atoms in elongated traps. The HFB-AX
solver based on B-spline techniques uses a hybrid MPI and OpenMP programming
model for parallel computation for distributed parallel computation, within a
node multi-threaded LAPACK and BLAS libraries are used to further enable
parallel calculations of large eigensystems. The MADNESS-HFB solver uses a
novel multi-resolution analysis based adaptive pseudo-spectral techniques to
enable fully parallel 3D calculations of very large systems. In this work we
present benchmark results for HFB-AX and MADNESS-HFB on ultracold trapped
fermions.Comment: Conference on Computational Physics (CCP 2011) Proceedin
On the kinks and dynamical phase transitions of alpha-helix protein chains
Heuristic insights into a physical picture of Davydov's solitonic model of
the one-dimensional protein chain are presented supporting the idea of a
non-equilibrium competition between the Davydov phase and a complementary,
dynamical- `ferroelectric' phase along the chainComment: small latex file with possible glue problems, just go on !, no
figures, small corrections with respect to the published text, follow-up work
to cond-mat/9304034 [PRE 47 (June 1993) R3818
Nonequilibrium Electron Interactions in Metal Films
Ultrafast relaxation dynamics of an athermal electron distribution is
investigated in silver films using a femtosecond pump-probe technique with 18
fs pulses in off-resonant conditions. The results yield evidence for an
increase with time of the electron-gas energy loss rate to the lattice and of
the free electron damping during the early stages of the electron-gas
thermalization. These effects are attributed to transient alterations of the
electron average scattering processes due to the athermal nature of the
electron gas, in agreement with numerical simulations
Descriptive Epidemiology of Bovine Tuberculosis in Michigan (1975–2010): Lessons Learned
Despite ongoing eradication efforts, bovine tuberculosis (BTB) remains a challenge in Michigan livestock and wildlife. The objectives of this study were to (1) review the epidemiology of BTB in Michigan cattle, privately owned cervids, and wildlife between 1975 and 2010 and (2) identify important lessons learned from the review and eradication strategies. BTB information was accessed from the Michigan BTB Eradication Project agencies. Cattle herds (49), privately owned deer herds (4), and wild white-tailed deer (668) were found infected with BTB during the review period. BTB has occurred primarily in counties located at the northern portion of the state's Lower Peninsula. Currently used BTB eradication strategies have successfully controlled BTB spread. However additional changes in BTB surveillance, prevention, and eradication strategies could improve eradication efforts
Size-Dependent Surface Plasmon Dynamics in Metal Nanoparticles
We study the effect of Coulomb correlations on the ultrafast optical dynamics
of small metal particles. We demonstrate that a surface-induced dynamical
screening of the electron-electron interactions leads to quasiparticle
scattering with collective surface excitations. In noble-metal nanoparticles,
it results in an interband resonant scattering of d-holes with surface
plasmons. We show that this size-dependent many-body effect manifests itself in
the differential absorption dynamics for frequencies close to the surface
plasmon resonance. In particular, our self-consistent calculations reveal a
strong frequency dependence of the relaxation, in agreement with recent
femtosecond pump-probe experiments.Comment: 8 pages + 4 figures, final version accepted to PR
Hole dynamics in noble metals
We present a detailed analysis of hole dynamics in noble metals (Cu and Au),
by means of first-principles many-body calculations. While holes in a
free-electron gas are known to live shorter than electrons with the same
excitation energy, our results indicate that d-holes in noble metals exhibit
longer inelastic lifetimes than excited sp-electrons, in agreement with
experiment. The density of states available for d-hole decay is larger than
that for the decay of excited electrons; however, the small overlap between d-
and sp-states below the Fermi level increases the d-hole lifetime. The impact
of d-hole dynamics on electron-hole correlation effects, which are of relevance
in the analysis of time-resolved two-photon photoemission experiments, is also
addressed.Comment: 4 pages, 2 figures, to appear in Phys. Rev. Let
MADNESS: A Multiresolution, Adaptive Numerical Environment for Scientific Simulation
MADNESS (multiresolution adaptive numerical environment for scientific
simulation) is a high-level software environment for solving integral and
differential equations in many dimensions that uses adaptive and fast harmonic
analysis methods with guaranteed precision based on multiresolution analysis
and separated representations. Underpinning the numerical capabilities is a
powerful petascale parallel programming environment that aims to increase both
programmer productivity and code scalability. This paper describes the features
and capabilities of MADNESS and briefly discusses some current applications in
chemistry and several areas of physics
Electron-lattice relaxation, and soliton structures and their interactions in polyenes
Density matrix renormalisation group calculations of a suitably parametrised
model of long polyenes (polyacetylene oligomers), which incorporates both long
range Coulomb interactions and adiabatic lattice relaxation, are presented. The
triplet and 2Ag states are found to have a 2-soliton and 4-soliton form,
respectively, both with large relaxation energies. The 1Bu state forms an
exciton-polaron and has a very small relaxation energy. The relaxed energy of
the 2Ag state lies below that of the 1Bu state. The soliton/anti-soliton pairs
are bound.Comment: RevTeX, 5 pages, 4 eps figures included using epsf. To appear in
Physical Review Letters. Fig. 1 fixed u
Coordinate-Space Hartree-Fock-Bogoliubov Description of Superfluid Fermi Systems
Properties of strongly interacting, two-component finite Fermi systems are
discussed within the recently developed coordinate-space
Hartree-Fock-Bogoliubov (HFB) code {\hfbax}. Two illustrative examples are
presented: (i) weakly bound deformed Mg isotopes, and (ii) spin-polarized
atomic condensates in a strongly deformed harmonic trap.Comment: 4 pages, 2 figures, ENAM 2008 conference proceedings (EPJA
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