8,615 research outputs found
alpha particle momentum distributions from 12C decaying resonances
The computed particle momentum distributions from the decay of
low-lying C resonances are shown. The wave function of the decaying
fragments is computed by means of the complex scaled hyperspherical adiabatic
expansion method. The large-distance part of the wave functions is crucial and
has to be accurately calculated. We discuss energy distributions, angular
distributions and Dalitz plots for the , and states of
C.Comment: 6 pages, 4 figures. Proceedings of the SOTANCP2008 conference held in
Strasbourg in May 200
Higher Loop Spin Field Correlators in D=4 Superstring Theory
We develop calculational tools to determine higher loop superstring
correlators involving massless fermionic and spin fields in four space time
dimensions. These correlation functions are basic ingredients for the
calculation of loop amplitudes involving both bosons and fermions in D=4
heterotic and superstring theories. To obtain the full amplitudes in Lorentz
covariant form the loop correlators of fermionic and spin fields have to be
expressed in terms of SO(1,3) tensors. This is one of the main achievements in
this work.Comment: 59 pages, 1 figure; v2: final version published in JHE
Three-body decays: structure, decay mechanism and fragment properties
We discuss the three-body decay mechanisms of many-body resonances. R-matrix
sequential description is compared with full Faddeev computation. The role of
the angular momentum and boson symmetries is also studied. As an illustration
we show the computed -particle energy distribution after the decay of
12C(1^+) resonance at 12.7 MeV.Comment: 4 pages, 3 figures. Proceedings of the workshop "Critical Stability
of Few-Body Quantum Systems" 200
Structure and three-body decay of Be resonances
The complex-rotated hyperspherical adiabatic method is used to study the
decay of low-lying Be resonances into one neutron and two
-particles. We investigate the six resonances above the break-up
threshold and below 6 MeV: , and . The
short-distance properties of each resonance are studied, and the different
angular momentum and parity configurations of the Be and He two-body
substructures are determined. We compute the branching ratio for sequential
decay via the Be ground state which qualitatively is consistent with
measurements. We extract the momentum distributions after decay directly into
the three-body continuum from the large-distance asymptotic structures. The
kinematically complete results are presented as Dalitz plots as well as
projections on given neutron and -energy. The distributions are
discussed and in most cases found to agree with available experimental data.Comment: 12 pages, 10 figures. To appear in Physical Review
Momentum distributions of -particles from decaying low-lying C-resonances
The complex scaled hyperspherical adiabatic expansion method is used to
compute momentum and energy distributions of the three -particles
emerging from the decay of low-lying C-resonances. The large distance
continuum properties of the wave functions are crucial and must be accurately
calculated. We discuss separately decays of natural parity states: two ,
one , three , one , two , one , and one of each of
unnatural parity, , , , . The lowest natural parity state
of each decays predominantly sequentially via the Be ground
state whereas other states including unnatural parity states predominantly
decay directly to the continuum. We present Dalitz plots and systematic
detailed momentum correlations of the emerging -particles.Comment: 11 pages, 7 figures, accepted for publication in Physical Review
Structure and bonding of halonium compounds
The geometrical parameters and the bonding in [D···X···D]+ halonium compounds, where D is a Lewis base with N as the donor atom and X is Cl, Br, or I, have been investigated through a combined structural and computational study. Cambridge Structural Database (CSD) searches have revealed linear and symmetrical [D···X···D]+ frameworks with neutral donors. By means of density functional theory (DFT), molecular electrostatic potential (MEP), and energy decomposition analyses (EDA) calculations, we have studied the effect of various halogen atoms (X) on the [D···X···D]+ framework, the effect of different nitrogen-donor groups (D) attached to an iodonium cation (X = I), and the influence of the electron density alteration on the [D···I···D]+ halonium bond by variation of the R substituents at the N-donor upon the symmetry, strength, and nature of the interaction. The physical origin of the interaction arises from a subtle interplay between electrostatic and orbital contributions (Ï-hole bond). Interaction energies as high as 45 kcal/mol suggest that halonium bonds can be exploited for the development of novel halonium transfer agents, in asymmetric halofunctionalization or as building blocks in supramolecular chemistry
Polynomial algebras and exact solutions of general quantum non-linear optical models I: Two-mode boson systems
We introduce higher order polynomial deformations of Lie algebra. We
construct their unitary representations and the corresponding single-variable
differential operator realizations. We then use the results to obtain exact
(Bethe ansatz) solutions to a class of 2-mode boson systems, including the
Boson-Einstein Condensate models as special cases. Up to an overall factor, the
eigenfunctions of the 2-mode boson systems are given by polynomials whose roots
are solutions of the associated Bethe ansatz equations. The corresponding
eigenvalues are expressed in terms of these roots. We also establish the
spectral equivalence between the BEC models and certain quasi-exactly solvable
Sch\"ordinger potentials.Comment: 20 pages, final version to appear in J. Phys. A: Math. Theor
Dual Instantons
We show how to map the Belavin-Polyakov instantons of the O(3)-nonlinear
model to a dual theory where they then appear as nontopological
solitons. They are stationary points of the Euclidean action in the dual
theory, and moreover, the dual action and the O(3)-nonlinear model
action agree on shell.Comment: 13 page
Few-body decay and recombination in nuclear astrophysics
Three-body continuum problems are investigated for light nuclei of
astrophysical relevance. We focus on three-body decays of resonances or
recombination via resonances or the continuum background. The concepts of
widths, decay mechanisms and dynamic evolution are discussed. We also discuss
results for the triple decay in connection with resonances and
density and temperature dependence rates of recombination into light nuclei
from -particles and neutrons.Comment: 9 pages, 8 figures. Proceedings of the 21st European Few Body
Conference held in Salamanca (Spain) in August-September 201
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