12,009 research outputs found
Coupled-channel continuum eigenchannel basis
The goal of this paper is to calculate bound, resonant and scattering states
in the coupled-channel formalism without relying on the boundary conditions at
large distances. The coupled-channel solution is expanded in eigenchannel bases
i.e. in eigenfunctions of diagonal Hamiltonians. Each eigenchannel basis may
include discrete and discretized continuum (real or complex energy) single
particle states. The coupled-channel solutions are computed through
diagonalization in these bases. The method is applied to a few two-channels
problems. The exact bound spectrum of the Poeschl-Teller potential is well
described by using a basis of real energy continuum states. For deuteron
described by Reid potential, the experimental energy and the S and D contents
of the wave function are reproduced in the asymptotic limit of the cutoff
energy. For the Noro-Taylor potential resonant state energy is well reproduced
by using the complex energy Berggren basis. It is found that the expansion of
the coupled-channel wave function in these eigenchannel bases require less
computational efforts than the use of any other basis. The solutions are stable
and converge as the cutoff energy increases.Comment: Accepted to be published in Physics Letters
Shadow poles in a coupled-channel problem calculated with Berggren basis
In coupled-channel models the poles of the scattering S-matrix are located on
different Riemann sheets. Physical observables are affected mainly by poles
closest to the physical region but sometimes shadow poles have considerable
effect, too. The purpose of this paper is to show that in coupled-channel
problem all poles of the S-matrix can be calculated with properly constructed
complex-energy basis. The Berggren basis is used for expanding the
coupled-channel solutions. The location of the poles of the S-matrix were
calculated and compared with an exactly solvable coupled-channel problem: the
one with the Cox potential. We show that with appropriately chosen Berggren
basis poles of the S-matrix including the shadow ones can be determined.Comment: 11 pages, 4 figures, 59 reference
Description of the proton and neutron radiative capture reactions in the Gamow shell model
We formulate the Gamow shell model (GSM) in coupled-channel (CC)
representation for the description of proton/neutron radiative capture
reactions and present the first application of this new formalism for the
calculation of cross-sections in mirror reactions 7Be(p,gamma)8B and
7Li(n,gamma)8Li. The GSM-CC formalism is applied to a translationally-invariant
Hamiltonian with an effective finite-range two-body interaction. Reactions
channels are built by GSM wave functions for the ground state 3/2- and the
first excited state 1/2- of 7Be/7Li and the proton/neutron wave function
expanded in different partial waves
The ambivalent shadow of the pre-Wilsonian rise of international law
The generation of American international lawyers who founded the American Society of International Law in 1906 and nurtured the soil for what has been retrospectively called a “moralistic legalistic approach to international relations” remains little studied. A survey of the rise of international legal literature in the U.S. from the mid-19th century to the eve of the Great War serves as a backdrop to the examination of the boosting effect on international law of the Spanish American War in 1898. An examination of the Insular Cases before the US Supreme Court is then accompanied by the analysis of a number of influential factors behind the pre-war rise of international law in the U.S. The work concludes with an examination of the rise of natural law doctrines in international law during the interwar period and the critiques addressed.by the realist founders of the field of “international relations” to the “moralistic legalistic approach to international relation
Gamow shell model description of radiative capture reactions LiBe and LiLi
According to standard stellar evolution, lithium abundance is believed to be
a useful indicator of the stellar age. However, many evolved stars like red
giants show huge fluctuations around expected theoretical abundances that are
not yet fully understood. The better knowledge of nuclear reactions that
contribute to the creation and destruction of lithium can help to solve this
puzzle. In this work we apply the Gamow shell model (GSM) formulated in the
coupled-channel representation (GSM-CC) to investigate the mirror radiative
capture reactions LiBe and LiLi. The
cross-sections are calculated using a translationally invariant Hamiltonian
with the finite-range interaction which is adjusted to reproduce spectra,
binding energies and one-nucleon separation energies in Li, Be. All
relevant , , and transitions from the initial continuum states to
the final bound states and of Li and Be are
included. We demonstrate that the -wave radiative capture of proton
(neutron) to the first excited state of Be (Li) is
crucial and increases the total astrophysical -factor by about 40 \%.Comment: arXiv admin note: text overlap with arXiv:1502.0163
On Steering Swarms
The main contribution of this paper is a novel method allowing an external
observer/controller to steer and guide swarms of identical and
indistinguishable agents, in spite of the agents' lack of information on
absolute location and orientation. Importantly, this is done via simple global
broadcast signals, based on the observed average swarm location, with no need
to send control signals to any specific agent in the swarm
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