21,711 research outputs found
Numerical computation of real or complex elliptic integrals
Algorithms for numerical computation of symmetric elliptic integrals of all
three kinds are improved in several ways and extended to complex values of the
variables (with some restrictions in the case of the integral of the third
kind). Numerical check values, consistency checks, and relations to Legendre's
integrals and Bulirsch's integrals are included
Tensor Forces and the Ground-State Structure of Nuclei
Two-nucleon momentum distributions are calculated for the ground states of
nuclei with mass number , using variational Monte Carlo wave functions
derived from a realistic Hamiltonian with two- and three-nucleon potentials.
The momentum distribution of pairs is found to be much larger than that of
pairs for values of the relative momentum in the range (300--600) MeV/c
and vanishing total momentum. This order of magnitude difference is seen in all
nuclei considered and has a universal character originating from the tensor
components present in any realistic nucleon-nucleon potential. The correlations
induced by the tensor force strongly influence the structure of pairs,
which are predominantly in deuteron-like states, while they are ineffective for
pairs, which are mostly in S states. These features should be
easily observable in two-nucleon knock-out processes, such as and .Comment: 4 pages including 3 figure
Dependence of two-nucleon momentum densities on total pair momentum
Two-nucleon momentum distributions are calculated for the ground states of
3He and 4He as a function of the nucleons' relative and total momenta. We use
variational Monte Carlo wave functions derived from a realistic Hamiltonian
with two- and three-nucleon potentials. The momentum distribution of pp pairs
is found to be much smaller than that of pn pairs for values of the relative
momentum in the range (300--500) MeV/c and vanishing total momentum. However,
as the total momentum increases to 400 MeV/c, the ratio of pp to pn pairs in
this relative momentum range grows and approaches the limit 1/2 for 3He and 1/4
for 4He, corresponding to the ratio of pp to pn pairs in these nuclei. This
behavior should be easily observable in two-nucleon knock-out processes, such
as A(e,e'pN).Comment: 3 pages, 3 figure
An experimental investigation of an advanced turboprop installation on a swept wing at subsonic and transonic speeds
An investigation was conducted in the Langley 16-Foot Transonic Tunnel to determine the effects of a turboprop-nacelle installation on the pressure distributions over a swept, supercritical wing. The tests were conducted at Mach numbers from 0.20 to 0.80, at angles of attack from 0 to 5 degrees, nacelle nozzle pressure ratios from 1.0 to 1.6, and at propeller tip speeds from 700 to 800 ft/sec. The results of this study indicate that the turboprop nacelle interference, with and without power, on a swept wing is greater on the inboard wing panel than on the outboard wing panel. The over-the-wing nacelle installation with the propeller upwash on the inboard panel had flow separation problems at a Mach number of 0.80. No severe flow separation problems appear to exist for either propeller rotation direction for the under-the-wing nacelle installation. The local flow disturbances caused by the under-the-wing nacelle installation were in general less severe than for the over-the-wing nacelle installation
Quantum Monte Carlo Calculations of Nuclei
The energies of , , and ground states, the
and scattering states of , the
ground states of , , and and the and
excited states of have been accurately calculated with the Green's
function Monte Carlo method using realistic models of two- and three-nucleon
interactions. The splitting of the isospin and
isospin , multiplets is also studied. The observed
energies and radii are generally well reproduced, however, some definite
differences between theory and experiment can be identified.Comment: 12 pages, 1 figur
The Coulomb Sum and Proton-Proton Correlations in Few-Body Nuclei
In simple models of the nuclear charge operator, measurements of the Coulomb
sum and the charge form factor of a nucleus directly determine the
proton-proton correlations. We examine experimental results obtained for
few-body nuclei at Bates and Saclay using models of the charge operator that
include both one- and two-body terms. Previous analyses using one-body terms
only have failed to reproduce experimental results. However, we find that the
same operators which have been used to successfully describe the charge form
factors also produce substantial agreement with measurements of the Coulomb
sum.Comment: 11 pages, Revtex version 3.0 with 3 Postscript figures appended, ANL
preprint PHY-7473-TH-9
Quantum Monte Carlo calculations of excited states in A = 6--8 nuclei
A variational Monte Carlo method is used to generate sets of orthogonal trial
functions, Psi_T(J^pi,T), for given quantum numbers in various light p-shell
nuclei. These Psi_T are then used as input to Green's function Monte Carlo
calculations of first, second, and higher excited (J^pi,T) states. Realistic
two- and three-nucleon interactions are used. We find that if the physical
excited state is reasonably narrow, the GFMC energy converges to a stable
result. With the combined Argonne v_18 two-nucleon and Illinois-2 three-nucleon
interactions, the results for many second and higher states in A = 6--8 nuclei
are close to the experimental values.Comment: Revised version with minor changes as accepted by Phys. Rev. C. 11
page
- …