10,096 research outputs found
Monte Carlo Study of Ordering and Domain Growth in a Class of fcc-Alloy Models
Ordering processes in fcc-alloys with composition A_3B (like Cu_3Au, Cu_3Pd,
CoPt_3 etc.) are investigated by Monte Carlo simulation within a class of
lattice models based on nearest-neighbor (NN) and second-neighbor (NNN)
interactions. Using an atom-vacancy exchange algorithm, we study the growth of
ordered domains following a temperature quench below the ordering spinodal. For
zero NNN-interactions we observe an anomalously slow growth of the domain size
L(t) \sim t^\alpha, where \alpha \sim 1/4 within our accessible timescales.
With increasing NNN-interactions domain growth becomes faster and \alpha
gradually approaches the value 1/2 as predicted by the conventional
Lifshitz-Allen-Cahn theory.Comment: 6 pages, 4 figure
Application of wavelets to singular integral scattering equations
The use of orthonormal wavelet basis functions for solving singular integral
scattering equations is investigated. It is shown that these basis functions
lead to sparse matrix equations which can be solved by iterative techniques.
The scaling properties of wavelets are used to derive an efficient method for
evaluating the singular integrals. The accuracy and efficiency of the wavelet
transforms is demonstrated by solving the two-body T-matrix equation without
partial wave projection. The resulting matrix equation which is characteristic
of multiparticle integral scattering equations is found to provide an efficient
method for obtaining accurate approximate solutions to the integral equation.
These results indicate that wavelet transforms may provide a useful tool for
studying few-body systems.Comment: 11 pages, 4 figure
Scattering Calculations with Wavelets
We show that the use of wavelet bases for solving the momentum-space
scattering integral equation leads to sparse matrices which can simplify the
solution. Wavelet bases are applied to calculate the K-matrix for
nucleon-nucleon scattering with the s-wave Malfliet-Tjon V potential. We
introduce a new method, which uses special properties of the wavelets, for
evaluating the singular part of the integral. Analysis of this test problem
indicates that a significant reduction in computational size can be achieved
for realistic few-body scattering problems.Comment: 26 pages, Latex, 6 eps figure
Evidenceâbased guidelines support integrated disease management as the optimal model of haemophilia care
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/122450/1/hae12997_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/122450/2/hae12997.pd
Evidenceâbased guidelines support integrated disease management as the optimal model of haemophilia care
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/122450/1/hae12997_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/122450/2/hae12997.pd
Generalized Schrieffer-Wolff Formalism for Dissipative Systems
We present a formalized perturbation theory for Markovian open systems in the
language of a generalized Schrieffer-Wolff (SW) transformation. A non-unitary
rotation decouples the unper- turbed steady states from all fast degrees of
freedom, in order to obtain an effective Liouvillian, that reproduces the exact
low excitation spectrum of the system. The transformation is derived in a
constructive way, yielding a perturbative expansion of the effective Liouville
operator. The presented formalism realizes an adiabatic elimination of fast
degrees of freedom to arbitrary orders in the perturbation. We exemplarily
employ the SW formalism to two generic open systems and discuss general
properties of the different orders of the perturbation.Comment: 11 pages, 1 figur
Microscopic Selection of Fluid Fingering Pattern
We study the issue of the selection of viscous fingering patterns in the
limit of small surface tension. Through detailed simulations of anisotropic
fingering, we demonstrate conclusively that no selection independent of the
small-scale cutoff (macroscopic selection) occurs in this system. Rather, the
small-scale cutoff completely controls the pattern, even on short time scales,
in accord with the theory of microscopic solvability. We demonstrate that
ordered patterns are dynamically selected only for not too small surface
tensions. For extremely small surface tensions, the system exhibits chaotic
behavior and no regular pattern is realized.Comment: 6 pages, 5 figure
Starburst in the Intragroup Medium of Stephan's Quintet
Based on new ISO mid-infrared observations and ground based and
near-infrared observations, we report the detection of a bright starburst in
the intragroup medium (IGM) of the famous compact group of galaxies Stephan's
Quintet (Source A in Fig.1). We demonstrate that this starburst is caused by a
collision between a high velocity (V 1000 km/sec) intruder galaxy
(NGC7318b) and the IGM of the group. While this is the only starburst known
today that is induced by a galaxy/cold-intergalactic-medium collision, it
provides new constraints to the theory for interaction-induced starbursts, and
may hint at a new mechanism for the star formation excess seen in more distant
clusters.Comment: 17 pages, 2 PS figures. Accepted by Ap
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