236 research outputs found
New treatment of breakup continuum in the method of continuum discretized coupled channels
A new method of pseudo-state discretization is proposed for the method of
continuum discretized coupled channels (CDCC) to deal with three-body breakup
processes. We propose real- and complex-range Gaussian bases for the
pseudo-state wave functions, and show that they form in good approximation a
complete set in the configuration space which is important for breakup
processes.
Continuous S-matrix elements are derived with the approximate completeness
from discrete ones calculated by CDCC.
Accuracy of the method is tested quantitatively for two realistic examples,
d+Ni scattering at 80 MeV and Li+Ca scattering at 156 MeV
with the satisfactory results. Possibility of application of the method to
four-body breakup processes is also discussed.Comment: 10 pages, 14 Postscript figures, uses REVTeX 4, submitted to Phys.
Rev.
Continuum-discretized coupled-channels method for four-body breakup reactions
Development of the method of CDCC (Continuum-Discretized Coupled-Channels)
from the level of three-body CDCC to that of four-body CDCC is reviewed.
Introduction of the pseudo-state method based on the Gaussian expansion method
for discretizing the continuum states of two-body and three-body projectiles
plays an essential role in the development. Furthermore, introduction of the
complex-range Gaussian basis functions is important to improve the CDCC for
nuclear breakup so as to accomplish that for Coulomb and nuclear breakup. A
successful application of the four-body CDCC to He+C scattering at
18 and 229.8 MeV is reported.Comment: Latex file of revtex4 class, 14 pages, 10 figures. A talk given at
the Workshop on Reaction Mechanisms for Rare Isotope Beams, Michigan State
University, March 9-12, 2005 (to appear in an AIP Conference Proceedings
The Brieva-Rook Localization of the Microscopic Nucleon-Nucleus Potential
The nonlocality of the microscopic nucleon-nucleus optical potential is
commonly localized by the Brieva-Rook approximation. The validity of the
localization is tested for the proton+Zr scattering at the incident
energies from 65 MeV to 800 MeV. The localization is valid in the wide
incident-energy range.Comment: 20 pages, 8 figure
Continuum-discretized coupled-channels method for four-body nuclear breakup in He+C scattering
We propose a fully quantum-mechanical method of treating four-body nuclear
breakup processes in scattering of a projectile consisting of three
constituents, by extending the continuum-discretized coupled-channels method.
The three-body continuum states of the projectile are discretized by
diagonalizing the internal
Hamiltonian of the projectile with the Gaussian basis functions. For
He+C scattering at 18 and 229.8 MeV, the validity of the method is
tested by convergence of the elastic and breakup cross sections with respect to
increasing the number of the basis functions. Effects of the four-body breakup
and the Borromean structure of He on the elastic and total reaction cross
sections are discussed.Comment: 5 pages, 6 figures, uses REVTeX 4, submitted to Phys. Rev.
Application of Absorbing Boundary Condition to Nuclear Breakup Reactions
Absorbing boundary condition approach to nuclear breakup reactions is
investigated. A key ingredient of the method is an absorbing potential outside
the physical area, which simulates the outgoing boundary condition for
scattered waves. After discretizing the radial variables, the problem results
in a linear algebraic equation with a sparse coefficient matrix, to which
efficient iterative methods can be applicable. No virtual state such as
discretized continuum channel needs to be introduced in the method. Basic
aspects of the method are discussed by considering a nuclear two-body
scattering problem described with an optical potential. We then apply the
method to the breakup reactions of deuterons described in a three-body direct
reaction model. Results employing the absorbing boundary condition are found to
accurately coincide with those of the existing method which utilizes
discretized continuum channels.Comment: 21 pages, 5 figures, RevTeX
Cosmological Constraints on Newton's Constant
We present cosmological constraints on deviations of Newton's constant at
large scales, analyzing latest cosmic microwave background (CMB) anisotropies
and primordial abundances of light elements synthesized by big bang
nucleosynthesis (BBN). BBN limits the possible deviation at typical scales of
BBN epoch, say at 10^8 \sim 10^12m, to lie between -5% and +1% of the
experimental value, and CMB restricts the deviation at larger scales 10^2 \sim
10^9pc to be between -26% and +66% at the 2\sigma confidence level. The
cosmological constraints are compared with the astronomical one from the
evolution of isochrone of globular clusters.Comment: 4 pages, 5 figure
Localization of Gravity on Brane Embedded in and
We address the localization of gravity on the Friedmann-Robertson-Walker type
brane embedded in either or bulk space,and derive two
definite limits between which the value of the bulk cosmological constant has
to lie in order to localize the graviton on the brane.The lower limit implies
that the brane should be either or 4d Minkowski in the
bulk.The positive upper limit indicates that the gravity can be trapped also on
curved brane in the bulk space.Some implications to recent
cosmological scenarios are also discussed.Comment: 18 pages, 3 figures, Latex fil
Evolution of Thick Walls in Curved Spacetimes
We generalize our previous thick shell formalism to incorporate any
codimension-1 thick wall with a peculiar velocity and proper thickness bounded
by arbitrary spacetimes. Within this new formulation we obtain the equation of
motion of a spherically symmetric dust thick shell immersed in vacuum as well
as in Friedmann-Robertson-Walker spacetimes.Comment: 8 pages, 1 figur
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