77,109 research outputs found
When will the United States grow out of its foreign debt?
In a 1989 article in this Review, John K. Hill argued that the mere aging of the baby boom generation would cause the United States to become a major capital exporter by the end of the century. To reach that conclusion, he assumed that rising U.S. capital outflows could be absorbed by the rest of the world without a decline in real interest rates. In this article, he considers the reasonableness of that assumption and reevaluates the accuracy of his earlier projections. ; Hill first examines the demographics of other major countries to see if they could support a rapid turnaround in the U.S. capital account. The results are decidedly negative. An analysis of capital flows based on demographic conditions in the United States, Japan, Germany, and the United Kingdom suggests that the United States could remain a net capital importer throughout this decade and into the early part of the next century. Despite these findings, Hill continues to support his earlier projections. He argues that new capital demands of former Communist and developing countries will help prevent a slide in interest rates and raise the international investment positions of all industrialized countries, including the United States.Debts, External ; Investments, Foreign - United States
Demographics and the foreign indebtedness of the United States
Population ; Debt ; Investments, Foreign - United States
Variational calculation of many-body wave functions and energies from density-functional theory
A generating coordinate is introduced into the exchange-correlation
functional of density-functional theory (DFT). The many-body wave function is
represented as a superposition of Kohn-Sham (KS) Slater determinants arising
from different values of the generating coordinate. This superposition is used
to variationally calculate many-body energies and wave functions from solutions
of the KS equation of DFT. The method works for ground and excited states, and
does not depend on identifying the KS orbitals and energies with physical ones.
Numerical application to the Helium isoelectronic series illustrates the
method's viability and potential.Comment: 4 pages, 2 tables, J. Chem. Phys., accepte
Using indirect methods to understand the impact of forced migration on long-term under-five mortality.
Despite the large numbers of displaced persons and the often-lengthy periods of displacement, little is known about the impact of forced migration on long-term under-five mortality. This paper looks at the Brass Method (and adaptations of this method) and the Preceding Birth Technique in combination with a classification of women by their migration and reproductive histories, in order to study the impact of forced migration on under-five mortality. Data came from the Demography of Forced Migration Project, a study on mortality, fertility and violence in the refugee and host populations of Arua District, Uganda and Yei River District, Sudan. Results indicate that women who did not migrate in a situation of conflict and women who repatriated before the age of 15, had children with the highest under-five mortality rates compared with women who were currently refugees and women who repatriated after the age of 15
Dimensional Deconstruction and Wess-Zumino-Witten Terms
A new technique is developed for the derivation of the Wess-Zumino-Witten
terms of gauged chiral lagrangians. We start in D=5 with a pure (mesonless)
Yang-Mills theory, which includes relevant gauge field Chern-Simons terms. The
theory is then compactified, and the effective D=4 lagrangian is derived using
lattice techniques, or ``deconstruction,'' where pseudoscalar mesons arise from
the lattice Wilson links. This yields the WZW term with the correct Witten
coefficient by way of a simple heuristic argument. We discover a novel WZW term
for singlet currents, that yields the full Goldstone-Wilczek current, and a
U(1) axial current for the skyrmion, with the appropriate anomaly structures. A
more detailed analysis is presented of the dimensional compactification of
Yang-Mills in D=5 into a gauged chiral lagrangian in D=4, heeding the
consistency of the D=4 and D=5 Bianchi identities. These dictate a novel
covariant derivative structure in the D=4 gauge theory, yielding a field
strength modified by the addition of commutators of chiral currents. The
Chern-Simons term of the pure D=5 Yang-Mills theory then devolves into the
correct form of the Wess-Zumino-Witten term with an index (the analogue of
N_{colors}=3) of N=D=5. The theory also has a Skyrme term with a fixed
coefficient.Comment: 29 pages, no figures; replacement fixes a typographical minus sign
error in eq.(16), an errant normalization factor, and clarifies some
discussion issue
Instrumentation for Millimeter-wave Magnetoelectrodynamic Investigations of Low-Dimensional Conductors and Superconductors
We describe instrumentation for conducting high sensitivity millimeter-wave
cavity perturbation measurements over a broad frequency range (40-200 GHz) and
in the presence of strong magnetic fields (up to 33 tesla). A Millimeter-wave
Vector Network Analyzer (MVNA) acts as a continuously tunable microwave source
and phase sensitive detector (8-350 GHz), enabling simultaneous measurements of
the complex cavity parameters (resonance frequency and Q-value) at a rapid
repetition rate (approx. 10 kHz). We discuss the principal of operation of the
MVNA and the construction of a probe for coupling the MVNA to various
cylindrical resonator configurations which can easily be inserted into a high
field magnet cryostat. We also present several experimental results which
demonstrate the potential of the instrument for studies of low-dimensional
conducting systems.Comment: 20 pages including fig
Behavior of Spherical Particles at Low Reynolds Numbers in a Fluctuating Translational Flow. Preliminary Experiments
The behavior of small spheres in non-steady translational flow
has been studied experimentally' for values of Reynolds nunber from 0
to 3000. The aim of the work was to improve our quantitative understanding
of particle transport in turbulent gaseous media, a process of
extreme importance in powerplants and energy transfer mechanisms.
Particles, subjected to strong sinusoidal oscillations parallel
to the direction of steady translation, were found to have changes in
average drag coefficient depending upon their translational Reynolds
number, the frequency and amplitude of the oscillations. When the
Reynolds number based on the sphere diameter was les s than 200,
the synunetric translational oscillation had negligible effect on the
aver age particle dr ago
For Reynolds numbers exceeding 300, the effective drag coefficient
was significantly increased in a particular frequency range. For
example, an increase in drag coefficient of 25 per cent was observed at
a Reynolds nwnber of 3000 when the amplitude of the oscillation was
2 per cent of the sphere diazneter and the disturbance frequency was approximately
the Strouhal frequency. The occurrence of the maximum
effect at frequencies between one and two times the Stroubal frequency
strongly suggests non-linear interaction between wake vortex shedding
and the oscillation in translational motions. Flow visualization studies
support this suggestion
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