1,447 research outputs found
Total Photoabsorption Cross Sections of A=6 Nuclei with Complete Final State Interaction
The total photoabsorption cross sections of 6He and 6Li are calculated
microscopically with full inclusion of the six-nucleon final state interaction
using semirealistic nucleon-nucleon potentials. The Lorentz Integral Transform
(LIT) method and the effective interaction approach for the hyperspherical
formalism are employed. While 6Li has a single broad giant resonance peak,
there are two well separated peaks for 6He corresponding to the breakup of the
neutron halo and the alpha core, respectively. The comparison with the few
available experimental data is discussed.Comment: LaTeX, 8 pages, 3 ps figure
Four-quark spectroscopy within the hyperspherical formalism
We present a generalization of the hyperspherical harmonic formalism to study
systems made of quarks and antiquarks of the same flavor. This generalization
is based on the symmetrization of the body wave function with respect to
the symmetric group using the Barnea and Novoselsky algorithm. The formalism is
applied to study four-quark systems by means of a constituent quark model
successful in the description of the two- and three-quark systems. The results
are compared to those obtained by means of variational approaches. Our analysis
shows that four-quark systems with exotic and non-exotic
quantum numbers may be bound independently of the mass of the quark.
and states become attractive only for larger mass of the quarks.Comment: 20 pages, 3 figure
Pro-p groups with few normal subgroups
Motivated by the study of pro-p groups With finite coclass, we consider the class of pro-p groups with few normal subgroups. This is not a well defined class and we offer several different definitions and study the connections between them. Furthermore, we propose a definition of periodicity for pro-p groups, thus, providing a general framework for some periodic patterns that have already been observed in the existing literature. We then focus oil examples and show that strikingly all the interesting examples not only have few normal Subgroups, but in addition have periodicity in the lattice of normal subgroups. (C) 2008 Elsevier Inc. All rights reserved
Faddeev approach to confined three-quark problems
We propose a method that allows for the efficient solution of the three-body
Faddeev equations in the presence of infinitely rising confinement
interactions. Such a method is useful in calculations of nonrelativistic and
especially semirelativistic constituent quark models. The convergence of the
partial wave series is accelerated and possible spurious contributions in the
Faddeev components are avoided. We demonstrate how the method works with the
example of the Goldstone-boson-exchange chiral quark model for baryons.Comment: 6 page
Benchmark Test Calculation of a Four-Nucleon Bound State
In the past, several efficient methods have been developed to solve the
Schroedinger equation for four-nucleon bound states accurately. These are the
Faddeev-Yakubovsky, the coupled-rearrangement-channel Gaussian-basis
variational, the stochastic variational, the hyperspherical variational, the
Green's function Monte Carlo, the no-core shell model and the effective
interaction hyperspherical harmonic methods. In this article we compare the
energy eigenvalue results and some wave function properties using the realistic
AV8' NN interaction. The results of all schemes agree very well showing the
high accuracy of our present ability to calculate the four-nucleon bound state.Comment: 17 pages, 1 figure
Quasi-particle interference and superconducting gap in a high-temperature superconductor Ca2-xNaxCuO2Cl2
High-transition-temperature (high-Tc) superconductivity is ubiquitous in the
cuprates containing CuO2 planes but each cuprate has its own character. The
study of the material dependence of the d-wave superconducting gap (SG) should
provide important insights into the mechanism of high-Tc. However, because of
the 'pseudogap' phenomenon, it is often unclear whether the energy gaps
observed by spectroscopic techniques really represent the SG. Here, we report
spectroscopic imaging scanning tunneling microscopy (SI-STM) studies of
nearly-optimally-doped Ca2-xNaxCuO2Cl2 (Na-CCOC) with Tc = 25 ~ 28 K. They
enable us to observe the quasi-particle interference (QPI) effect in this
material, through which unambiguous new information on the SG is obtained. The
analysis of QPI in Na-CCOC reveals that the SG dispersion near the gap node is
almost identical to that of Bi2Sr2CaCu2Oy (Bi2212) at the same doping level,
while Tc of Bi2212 is 3 times higher than that of Na-CCOC. We also find that SG
in Na-CCOC is confined in narrower energy and momentum ranges than Bi2212. This
explains at least in part the remarkable material dependence of TcComment: 13pages, 4fig
Calculation of the Alpha--Particle Ground State within the Hyperspherical Harmonic Basis
The problem of calculating the four--nucleon bound state properties for the
case of realistic two- and three-body nuclear potentials is studied using the
hyperspherical harmonic (HH) approach. A careful analysis of the convergence of
different classes of HH functions has been performed. A restricted basis is
chosen to allow for accurate estimates of the binding energy and other
properties of the 4He ground state. Results for various modern two-nucleon and
two- plus three-nucleon interactions are presented. The 4He asymptotic
normalization constants for separation in 2+2 and 1+3 clusters are also
computed.Comment: 29 pages, 4 figures, 11 tables, revtex
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