42,525 research outputs found
Interaction effects of a child tax credit, national health insurance, and assured child support
If the government offered a refundable tax credit for children, national health insurance, and an assured child support benefit to all families with children - poor families as well as nonpoor families - what would happen to poverty, welfare dependency, and other related issues? The authors simulate the effects of each program operating on its own and of all three acting in concert. They find that the impacts of the programs interacting with one another would be much larger than the sum of the impacts produced by each program alone. With the three programs in place, the poverty rate would fall by 43 percent, the AFDC caseload would shrink by 22 percent, and the annual incomes of poor families would rise by $2500. In addition, AFDC recipients would work more hours. Data come from the 1987 Survey of Income and Program Participation.
Time-dependent coupled-cluster method for atomic nuclei
We study time-dependent coupled-cluster theory in the framework of nuclear
physics. Based on Kvaal's bi-variational formulation of this method [S. Kvaal,
arXiv:1201.5548], we explicitly demonstrate that observables that commute with
the Hamiltonian are conserved under time evolution. We explore the role of the
energy and of the similarity-transformed Hamiltonian under real and imaginary
time evolution and relate the latter to similarity renormalization group
transformations. Proof-of-principle computations of He-4 and O-16 in small
model spaces, and computations of the Lipkin model illustrate the capabilities
of the method.Comment: 10 pages, 9 pdf figure
Harnack Inequality and Regularity for a Product of Symmetric Stable Process and Brownian Motion
In this paper, we consider a product of a symmetric stable process in
and a one-dimensional Brownian motion in . Then we
define a class of harmonic functions with respect to this product process. We
show that bounded non-negative harmonic functions in the upper-half space
satisfy Harnack inequality and prove that they are locally H\"older continuous.
We also argue a result on Littlewood-Paley functions which are obtained by the
-harmonic extension of an function.Comment: 23 page
Quantum lattice gases and their invariants
The one particle sector of the simplest one dimensional quantum lattice gas
automaton has been observed to simulate both the (relativistic) Dirac and
(nonrelativistic) Schroedinger equations, in different continuum limits. By
analyzing the discrete analogues of plane waves in this sector we find
conserved quantities corresponding to energy and momentum. We show that the
Klein paradox obtains so that in some regimes the model must be considered to
be relativistic and the negative energy modes interpreted as positive energy
modes of antiparticles. With a formally similar approach--the Bethe ansatz--we
find the evolution eigenfunctions in the two particle sector of the quantum
lattice gas automaton and conclude by discussing consequences of these
calculations and their extension to more particles, additional velocities, and
higher dimensions.Comment: 19 pages, plain TeX, 11 PostScript figures included with epsf.tex
(ignore the under/overfull \vbox error messages
Lithological maps of selected Apollo 14 Breccia samples
A booklet of mapped surfaces of some Apollo 14 samples was prepared as an intermediate step towards the preparation of a new Apollo 14 sample catalog. It contains recently obtained observations and pictures of some of the largest and less well documented Apollo breccia samples. Some of the samples (14303, 14305, 14306, and 14311) were chosen because they have large sawn surfaces. These were dusted and mapped using a binocular microscope through the window of the nitrogen cabinet
A Na I Absorption Map of the Small-Scale Structure in the Interstellar Gas Toward M15
Using the DensePak fiber optic array on the KPNO WIYN telescope, we have
obtained high S/N echelle spectra of the Na I D wavelength region toward the
central 27" x 43" of the globular cluster M15 at a spatial resolution of 4".
The spectra exhibit significant interstellar Na I absorption at LSR velocities
of +3 km/s (LISM component) and +68 km/s (IVC component). Both components vary
appreciably in strength on these scales. The derived Na I column densities
differ by a factor of 4 across the LISM absorption map and by a factor of 16
across the IVC map. Assuming distances of 500 pc and 1500 pc for the LISM and
IVC clouds, these maps show evidence of significant ISM structure down to the
minimum scales of 2000 AU and 6000 AU probed in these absorbers. The
smallest-scale N(Na I) variations observed in the M15 LISM and IVC maps are
typically comparable to or higher than the values found at similar scales in
previous studies of interstellar Na I structure toward binary stars. The
physical implications of the small and larger-scale Na I features observed in
the M15 maps are discussed in terms of variations in the H I column density as
well as in the Na ionization equilibrium.Comment: 11 pages, 3 figures, accepted for publication in ApJ Letter
Spherically Symmetric Solutions in M\o ller's Tetrad Theory of Gravitation
The general solution of M\o ller's field equations in case of spherical
symmetry is derived. The previously obtained solutions are verified as special
cases of the general solution.Comment: LaTeX2e with AMS-LaTeX 1.2, 8 page
On the role of the UV and X-ray radiation in driving a disk wind in X-ray binaries
X-ray heating of the photosphere of an accretion disk is a possible mechanism
to produce strong, broad UV emission lines in low mass X-ray binaries (LMXBs).
However, detailed photoionization calculations show that this mechanism fails
to produce sufficient emission measure. We present the results of
hydrodynamical calculations of the disk photosphere irradiated by strong
X-rays. We attempt to determine whether LMXBs can harbor significant UV-driven
disk winds despite the effects of X-ray ionization. Such winds would be a
likely candidate for the site of emission of UV lines and may better explain
the observations than the X-ray heated disk photosphere. We find that the local
disk radiation cannot launch a wind from the disk because of strong ionizing
radiation from the central object. Unphysically high X-ray opacities would be
required to shield the UV emitting disk and allow the line force to drive a
disk wind. However the same X-ray radiation that inhibits line driving heats
the disk and can produce a hot bipolar wind or corona above the disk. To assess
the impact of X-ray heating upon driving of a disk wind by the line force in
any system with an accretion disk we derive analytic formulae. In particular,
we compare results of line-driven disk wind models for accretion disks in LMXBs
and active galactic nuclei. The latter show spectral features associated with a
strong and fast disk wind. The key parameter determining the role of the line
force is not merely the presence of the luminous UV zone in the disk and the
presence of the X-rays, but also the distance of this UV zone from the center.Comment: LaTeX, 34 pages, contains color figures, to appear in Ap
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