8,547 research outputs found
Three-body halos. V. Computations of continuum spectra for Borromean nuclei
We solve the coordinate space Faddeev equations in the continuum. We employ
hyperspherical coordinates and provide analytical expressions allowing easy
computation of the effective potentials at distances much larger than the
ranges of the interactions where only s-waves in the different Jacobi
coordinates couple. Realistic computations are carried out for the Borromean
halo nuclei 6He (n+n+\alpha) for J\pi = 0+-, 1+-, 2+- and 11Li (n+n+9Li) for
(1/2)+-, (3/2)+-, (5/2)+-. Ground state properties, strength functions, Coulomb
dissociation cross sections, phase shifts, complex S-matrix poles are computed
and compared to available experimental data. We find enhancements of the
strength functions at low energies and a number of low-lying S-matrix poles.Comment: 35 pages, 14 figure
The structure of the atomic helium trimers: Halos and Efimov states
The Faddeev equations for the atomic helium-trimer systems are solved
numerically with high accuracy both for the most sophisticated realistic
potentials available and for simple phenomenological potentials. An efficient
numerical procedure is described. The large-distance asymptotic behavior,
crucial for weakly bound three-body systems, is described almost analytically
for arbitrary potentials. The Efimov effect is especially considered. The
geometric structures of the bound states are quantitatively investigated. The
accuracy of the schematic models and previous computations is comparable, i.e.
within 20% for the spatially extended states and within 40% for the smaller
^4He-trimer ground state.Comment: 32 pages containing 7 figures and 6 table
Three-Body Halos. II. from Two- to Three-Body Asymptotics
The large distance behavior of weakly bound three-body systems is
investigated. The Schr\"{o}dinger equation and the Faddeev equations are
reformulated by an expansion in eigenfunctions of the angular part of a
corresponding operator. The resulting coupled set of effective radial equations
are then derived. Both two- and three-body asymptotic behavior are possible and
their relative importance is studied for systems where subsystems may be bound.
The system of two nucleons outside a core is studied numerically in detail and
the character of possible halo structure is pointed out and investigated.Comment: 16 pages, compressed and uuencoded PosrScript file, IFA-94/3
Phase equivalent potentials for three-body halos
We compare the properties of three-body systems obtained with two-body
potentials with Pauli forbidden states and with the corresponding phase
equivalent two-body potentials. In the first case the forbidden states are
explicitly excluded in the calculation. Differences arise due to the off-shell
properties of these on-shell equivalent potentials. We use the adiabatic
hyperspherical method to formulate a practical prescription to exclude Pauli
forbidden states in three-body calculations. Schematic as well as realistic
potentials are used. Almost indistinguishable results are obtained.Comment: 18 pages, 6 figure
Probing global aspects of a geometry by the self-force on a charge: Spherical thin-shell wormholes
The self-interaction for a static point charge in the space-time of a
thin-shell wormhole constructed connecting two identical Schwarzschild
geometries is calculated in a series expansion. The electrostatic self-force is
evaluated numerically. It is found to be attractive towards the throat except
for some values of the throat radius proximate to the value of the
Schwarzschild horizon for which the force is repulsive or attractive depending
on the position of the charge. The result differs from the self-force in the
space-time of the Schwarzschild black hole, where it is always repulsive from
the center. Although these wormhole and black hole geometries are locally
indistinguishable, the different topologies of both backgrounds are manifested
in the electrostatic field of a point charge.Comment: 17 pages, 4 figue
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