12,325 research outputs found
Scaling Behavior of Driven Interfaces Above the Depinning Transition
We study the depinning transition for models representative of each of the
two universality classes of interface roughening with quenched disorder. For
one of the universality classes, the roughness exponent changes value at the
transition, while the dynamical exponent remains unchanged. We also find that
the prefactor of the width scales with the driving force. We propose several
scaling relations connecting the values of the exponents on both sides of the
transition, and discuss some experimental results in light of these findings.Comment: Revtex 3.0, 4 pages in PRL format + 5 figures (available at
ftp://jhilad.bu.edu/pub/abbhhss/ma-figures.tar.Z ) submitted to Phys Rev Let
Energy dependence of non-local potentials
Recently a variety of studies have shown the importance of including
non-locality in the description of reactions. The goal of this work is to
revisit the phenomenological approach to determining non-local optical
potentials from elastic scattering. We perform a analysis of neutron
elastic scattering data off Ca, Zr and Pb at energies MeV, assuming a Perey and Buck or Tian, Pang, and Ma non-local
form for the optical potential. We introduce energy and asymmetry dependencies
in the imaginary part of the potential and refit the data to obtain a global
parameterization. Independently of the starting point in the minimization
procedure, an energy dependence in the imaginary depth is required for a good
description of the data across the included energy range. We present two
parameterizations, both of which represent an improvement over the original
potentials for the fitted nuclei as well as for other nuclei not included in
our fit. Our results show that, even when including the standard Gaussian
non-locality in optical potentials, a significant energy dependence is required
to describe elastic-scattering data.Comment: 6 pages, 3 figures, accepted by Phys. Rev. C Rapid Communicatio
Li in a Three-Body Model with Realistic Forces: Separable vs. Non-separable Approach
{\bf Background:} Deuteron induced reactions are widely used to probe nuclear
structure and astrophysical information. Those (d,p) reactions may be viewed as
three-body reactions and described with Faddeev techniques.
{\bf Purpose:} Faddeev equations in momentum space have a long tradition of
utilizing separable interactions in order to arrive at sets of coupled integral
equations in one variable. However, it needs to be demonstrated that their
solution based on separable interactions agrees exactly with solutions based on
non-separable forces.
{\bf Results:} The ground state of Li is calculated via momentum space
Faddeev equations using the CD-Bonn neutron-proton force and a Woods-Saxon type
neutron(proton)-He force. For the latter the Pauli-forbidden -wave bound
state is projected out. This result is compared to a calculation in which the
interactions in the two-body subsystems are represented by separable
interactions derived in the Ernst-Shakin-Thaler framework.
{\bf Conclusions:} We find that calculations based on the separable
representation of the interactions and the original interactions give results
that agree to four significant figures for the binding energy, provided an
off-shell extension of the EST representation is employed in both subsystems.
The momentum distributions computed in both approaches also fully agree with
each other
Ciclo de vida do Crinipellis perniciosa no cupuaçuzeiro (Theobroma grandiflorum).
Introducão; A doença; O patógeno; Epidemiologia; Ciclo das relacões patógeno-hospedeiro.bitstream/item/36503/1/Doc64.pd
Combined method to extract spectroscopic information
Spectroscopic factors (SF) play an important role in nuclear physics and
astrophysics. The traditional method of extracting SF from direct transfer
reactions suffers from serious ambiguities. We discuss a modified method which
is based on including the asymptotic normalization coefficient (ANC) of the
overlap functions into the transfer analysis. In the modified method the
contribution of the external part of the reaction amplitude, typically
dominant, is fixed and the SF is determined from fitting the internal part. We
illustrate the modified method with reactions on , and targets at different energies. The
modified method allows one to extract the SF, which do not depend on the shape
of the single-particle nucleon-target interaction, and has the potential of
improving the reliability and accuracy of the structure information. This is
specially important for nuclei on dripline, where not much is known.Comment: accepted in Phys. Rev. C, 4 pages and 2 figure
Comment on: Kinetic Roughening in Slow Combustion of Paper
We comment on a recent Letter by Maunuksela et al. [Phys. Rev. Lett. 79, 1515
(1997)].Comment: 1 page, 1 figure, http://polymer.bu.edu/~hmakse/Home.htm
- …