21,157 research outputs found
Perturbation Theory around Non-Nested Fermi Surfaces I. Keeping the Fermi Surface Fixed
The perturbation expansion for a general class of many-fermion systems with a
non-nested, non-spherical Fermi surface is renormalized to all orders. In the
limit as the infrared cutoff is removed, the counterterms converge to a finite
limit which is differentiable in the band structure. The map from the
renormalized to the bare band structure is shown to be locally injective. A new
classification of graphs as overlapping or non-overlapping is given, and
improved power counting bounds are derived from it. They imply that the only
subgraphs that can generate factorials in the order of the
renormalized perturbation series are indeed the ladder graphs and thus give a
precise sense to the statement that `ladders are the most divergent diagrams'.
Our results apply directly to the Hubbard model at any filling except for
half-filling. The half-filled Hubbard model is treated in another place.Comment: plain TeX with postscript figures in a uuencoded gz-compressed tar
file. Put it on a separate directory before unpacking, since it contains
about 40 files. If you have problems, requests or comments, send e-mail to
[email protected]
Revealed Preferences for Car Tax Cuts: an Empirical Study of Perceived Fiscal Incidence
Voting in an election in which elimination of the local car tax is the central issue shows how a highly visible universal tax cut can prevail in the electoral process even if benefits are skewed toward upper income households. These results are consistent with positive models of fiscal structure choice in which fiscal systems are the consequence of support maximizing politicians attempting to supply net benefits to easily identifiable interest groups without generating significant opposition from other groups.personal property taxes, tax revolt,targeted universalism
Functional Equations and the Generalised Elliptic Genus
We give a new derivation and characterisation of the generalised elliptic
genus of Krichever-H\"ohn by means of a functional equation.Comment: To be published in the collection honouring Francesco Calogero's
70-th birthda
State Higher Education Spending and the Tax Revolt
Public effort in support of higher education – measured as state funding per thousand dollars of personal income – has declined by thirty percent since the late 1970s. During this time period many states implemented Tax and Expenditure Limits and/or supermajority requirements for tax increases. We use a forty-eight state panel from 1961 to 2001 to evaluate the effect of these tax revolt institutions for state effort on behalf of higher education. These provisions have a statistically significant and economically large impact on the timing and magnitude of this decline in state effort. An understanding of the fiscal environment caused by these provisions is critical for the future of state-supported higher education.State higher education spending, tax revolt, Tax and Expenditure Limits
The Temperature and Density Structure of the Solar Corona. I. Observations of the Quiet Sun with the EUV Imaging Spectrometer (EIS) on Hinode
Measurements of the temperature and density structure of the solar corona
provide critical constraints on theories of coronal heating. Unfortunately, the
complexity of the solar atmosphere, observational uncertainties, and the
limitations of current atomic calculations, particularly those for Fe, all
conspire to make this task very difficult. A critical assessment of plasma
diagnostics in the corona is essential to making progress on the coronal
heating problem. In this paper we present an analysis of temperature and
density measurements above the limb in the quiet corona using new observations
from the EUV Imaging Spectrometer (EIS) on \textit{Hinode}. By comparing the Si
and Fe emission observed with EIS we are able to identify emission lines that
yield consistent emission measure distributions. With these data we find that
the distribution of temperatures in the quiet corona above the limb is strongly
peaked near 1 MK, consistent with previous studies. We also find, however, that
there is a tail in the emission measure distribution that extends to higher
temperatures. EIS density measurements from several density sensitive line
ratios are found to be generally consistent with each other and with previous
measurements in the quiet corona. Our analysis, however, also indicates that a
significant fraction of the weaker emission lines observed in the EIS
wavelength ranges cannot be understood with current atomic data.Comment: Submitted to Ap
Ultralight reactive metal foams produced as structural shapes in space: System design
This autonomous experiment for foaming metals in space involved: (1) payload support structure; (2) furnace and foaming apparatus; (3) electronic controls; (4) battery power; and (5) metallurgy. Emphasis was laid on a modular design which was easily modifiable and which offered maximum durability, safety, and failure tolerance
Lunar Resource Assessment: an Industry Perspective
The goals of the U.S. space program are to return to the Moon, establish a base, and continue onward to Mars. To accomplish this in a relatively short time frame and to avoid the high costs of transporting materials from the Earth, resources on the Moon will need to be mined. Oxygen will be one of the most important resources, to be used as a rocket propellant and for life support. Ilmenite and lunar regolith have both been considered as ores for the production of oxygen. Resource production on the Moon will be a very important part of the U.S. space program. To produce resources we must explore to identify the location of ore or feedback and calculate the surface and underground reserves. Preliminary resource production tests will provide the information that can be used in final plant design. Bechtel Corporation's experience in terrestrial engineering and construction has led to an interest in lunar resource assessment leading to the construction of production facilities on the Moon. There is an intimate link between adequate resource assessment to define feedstock quantity and quality, material processing requirements, and the successful production of lunar oxygen. Although lunar resource assessment is often viewed as a research process, the engineering and production aspects are very important to consider. Resource production often requires the acquisition of different types, scales, or resolutions of data than that needed for research, and it is needed early in the exploration process. An adequate assessment of the grade, areal extent, and depth distribution of the resources is a prerequisite to mining. The need for a satisfactory resource exploration program using remote sensing techniques, field sampling, and chemical and physical analysis is emphasized. These data can be used to define the ore for oxygen production and the mining, processing facilities, and equipment required
Unseen Affective Faces Influence Person Perception Judgments in Schizophrenia.
To demonstrate the influence of unconscious affective processing on consciously processed information among people with and without schizophrenia, we used a continuous flash suppression (CFS) paradigm to examine whether early and rapid processing of affective information influences first impressions of structurally neutral faces. People with and without schizophrenia rated visible neutral faces as more or less trustworthy, warm, and competent when paired with unseen smiling or scowling faces compared to when paired with unseen neutral faces. Yet, people with schizophrenia also exhibited a deficit in explicit affect perception. These findings indicate that early processing of affective information is intact in schizophrenia but the integration of this information with semantic contexts is problematic. Furthermore, people with schizophrenia who were more influenced by smiling faces presented outside awareness reported experiencing more anticipatory pleasure, suggesting that the ability to rapidly process affective information is important for anticipation of future pleasurable events
Reconstruction of primordial density fields
The Monge-Ampere-Kantorovich (MAK) reconstruction is tested against
cosmological N-body simulations. Using only the present mass distribution
sampled with particles, and the assumption of homogeneity of the primordial
distribution, MAK recovers for each particle the non-linear displacement field
between its present position and its Lagrangian position on a primordial
uniform grid. To test the method, we examine a standard LCDM N-body simulation
with Gaussian initial conditions and 6 models with non-Gaussian initial
conditions: a chi-squared model, a model with primordial voids and four weakly
non-Gaussian models. Our extensive analyses of the Gaussian simulation show
that the level of accuracy of the reconstruction of the nonlinear displacement
field achieved by MAK is unprecedented, at scales as small as about 3 Mpc. In
particular, it captures in a nontrivial way the nonlinear contribution from
gravitational instability, well beyond the Zel'dovich approximation. This is
also confirmed by our analyses of the non-Gaussian samples. Applying the
spherical collapse model to the probability distribution function of the
divergence of the displacement field, we also show that from a
well-reconstructed displacement field, such as that given by MAK, it is
possible to accurately disentangle dynamical contributions induced by
gravitational clustering from possible initial non-Gaussianities, allowing one
to efficiently test the non-Gaussian nature of the primordial fluctuations. In
addition, a simple application of MAK using the Zel'dovich approximation allows
one to also recover accurately the present-day peculiar velocity field on
scales of about 8 Mpc.Comment: Version to appear in MNRAS, 24 pages, 21 figures appearing (uses 35
figure files), 1 tabl
A Proof of Luttinger Theorem
A rigorous and simple perturbative proof of Luttinger's theorem is sketched
for Fermi liquids in two and three dimensions. It is proved that in the finite
volume, the quasi-particle density is independent of the interaction strength.
The thermodynamic limit is then controlled to all orders in perturbation
theory.Comment: 7 page
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