680 research outputs found
Toward a Spin- and Parity-Independent Nucleon-Nucleon Potential
A supersymmetric inversion method is applied to the singlet and
neutron-proton elastic phase shifts. The resulting central potential
has a one-pion-exchange (OPE) long-range behavior and a parity-independent
short-range part; it fits inverted data well. Adding a regularized OPE tensor
term also allows the reproduction of the triplet , and
phase shifts as well as of the deuteron binding energy. The potential is thus
also spin-independent (except for the OPE part) and contains no spin-orbit
term. These important simplifications of the neutron-proton interaction are
shown to be possible only if the potential possesses Pauli forbidden bound
states, as proposed in the Moscow nucleon-nucleon model.Comment: 9 pages, RevTeX, 5 ps figure
Supersymmetric transformations for coupled channels with threshold differences
The asymptotic behaviour of the superpotential of general SUSY
transformations for a coupled-channel Hamiltonian with different thresholds is
analyzed. It is shown that asymptotically the superpotential can tend to a
diagonal matrix with an arbitrary number of positive and negative entries
depending on the choice of the factorization solution. The transformation of
the Jost matrix is generalized to "non-conservative" SUSY transformations
introduced in Sparenberg et al (2006 J. Phys. A: Math. Gen. 39 L639). Applied
to the zero initial potential the method permits to construct superpartners
with a nontrivially coupled Jost-matrix. Illustrations are given for two- and
three-channel cases.Comment: 17 pages, 3 explicit examples and figures adde
Microscopic description of the beta delayed deuteron emission from \bbox{^6}He
The beta delayed deuteron emission from He is studied in a dynamical
microscopic cluster model. This model gives a reasonably good description for
all the subsystems of He and Li in a coherent way, without any free
parameter. The beta decay transition probability to the Li ground state is
underestimated by a few percents. The theoretical beta delayed deuteron
spectrum is close to experiment but it is also underestimated by about a factor
1.7. We argue that, in spite of their different magnitudes, both
underestimations might have a common origin. The model confirms that the
neutron halo part of the He wave function plays a crucial role in quenching
the beta decay toward the + d channel.Comment: LATEX with REVTEX, Submitted to Phys. Rev. C, 11 pages, 3 figures
(not included) are available upon request. ATOMKI-93/
Eigenphase preserving two-channel SUSY transformations
We propose a new kind of supersymmetric (SUSY) transformation in the case of
the two-channel scattering problem with equal thresholds, for partial waves of
the same parity. This two-fold transformation is based on two imaginary
factorization energies with opposite signs and with mutually conjugated
factorization solutions. We call it an eigenphase preserving SUSY
transformation as it relates two Hamiltonians, the scattering matrices of which
have identical eigenphase shifts. In contrast to known phase-equivalent
transformations, the mixing parameter is modified by the eigenphase preserving
transformation.Comment: 16 pages, 1 figur
Canonical-basis solution of the Hartree-Fock-Bogoliubov equation on three-dimensional Cartesian mesh
A method is presented to obtain the canonical-form solutions of the HFB
equation for atomic nuclei with zero-range interactions like the Skyrme force.
It is appropriate to describe pairing correlations in the continuum in
coordinate-space representations. An improved gradient method is used for
faster convergences under constraint of orthogonality between orbitals. To
prevent high-lying orbitals to shrink into a spatial point, a repulsive
momentum dependent force is introduced, which turns out to unveil the nature of
high-lying canonical-basis orbitals. The asymptotic properties at large radius
and the relation with quasiparticle states are discussed for the obtained
canonical basis.Comment: 23 pages including 17 figures, REVTeX4, revised version, scheduled to
appear in Phys. Rev. C, Vol.69, No.
Clarification of the relationship between bound and scattering states in quantum mechanics: Application to 12C + alpha
Using phase-equivalent supersymmetric partner potentials, a general result
from the inverse problem in quantum scattering theory is illustrated, i.e.,
that bound-state properties cannot be extracted from the phase shifts of a
single partial wave, as a matter of principle. In particular, recent R-matrix
analyses of the 12C + alpha system, extracting the asymptotic normalization
constant of the 2+ subthreshold state, C12, from the l=2 elastic-scattering
phase shifts and bound-state energy, are shown to be unreliable. In contrast,
this important constant in nuclear astrophysics can be deduced from the
simultaneous analysis of the l=0, 2, 4, 6 partial waves in a simplified
potential model. A new supersymmetric inversion potential and existing models
give C12=144500+-8500 fm-1/2.Comment: Expanded version (50% larger); three errors corrected (conversion of
published reduced widths to ANCs); nine references added, one remove
Breakup reaction models for two- and three-cluster projectiles
Breakup reactions are one of the main tools for the study of exotic nuclei,
and in particular of their continuum. In order to get valuable information from
measurements, a precise reaction model coupled to a fair description of the
projectile is needed. We assume that the projectile initially possesses a
cluster structure, which is revealed by the dissociation process. This
structure is described by a few-body Hamiltonian involving effective forces
between the clusters. Within this assumption, we review various reaction
models. In semiclassical models, the projectile-target relative motion is
described by a classical trajectory and the reaction properties are deduced by
solving a time-dependent Schroedinger equation. We then describe the principle
and variants of the eikonal approximation: the dynamical eikonal approximation,
the standard eikonal approximation, and a corrected version avoiding Coulomb
divergence. Finally, we present the continuum-discretized coupled-channel
method (CDCC), in which the Schroedinger equation is solved with the projectile
continuum approximated by square-integrable states. These models are first
illustrated by applications to two-cluster projectiles for studies of nuclei
far from stability and of reactions useful in astrophysics. Recent extensions
to three-cluster projectiles, like two-neutron halo nuclei, are then presented
and discussed. We end this review with some views of the future in
breakup-reaction theory.Comment: Will constitute a chapter of "Clusters in Nuclei - Vol.2." to be
published as a volume of "Lecture Notes in Physics" (Springer
Vortex line in a neutral finite-temperature superfluid Fermi gas
The structure of an isolated vortex in a dilute two-component neutral
superfluid Fermi gas is studied within the context of self-consistent
Bogoliubov-de Gennes theory. Various thermodynamic properties are calculated
and the shift in the critical temperature due to the presence of the vortex is
analyzed. The gapless excitations inside the vortex core are studied and a
scheme to detect these states and thus the presence of the vortex is examined.
The numerical results are compared with various analytical expressions when
appropriate.Comment: 8 pages, 6 embedded figure
On the construction of non-Hermitian Hamiltonians with all-real spectra through supersymmetric algorithms
The energy spectra of two different quantum systems are paired through
supersymmetric algorithms. One of the systems is Hermitian and the other is
characterized by a complex-valued potential, both of them with only real
eigenvalues in their spectrum. The superpotential that links these systems is
complex-valued, parameterized by the solutions of the Ermakov equation, and may
be expressed either in nonlinear form or as the logarithmic derivative of a
properly chosen complex-valued function. The non-Hermitian systems can be
constructed to be either parity-time-symmetric or non-parity-time-symmetric.Comment: 9 pages, 2 figures (affiliation institution corrected
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