1,645 research outputs found
Noncommutative Geometry and The Ising Model
The main aim of this work is to present the interpretation of the Ising type
models as a kind of field theory in the framework of noncommutative geometry.
We present the method and construct sample models of field theory on discrete
spaces using the introduced tools of discrete geometry. We write the action for
few models, then we compare them with various models of statistical physics. We
construct also the gauge theory with a discrete gauge group.Comment: 12 pages, LaTeX, TPJU - 18/92, December 199
The Employment, Earnings, and Income of Less-Skilled Workers over the Business Cycle
In this paper, I examine the effect of business cycles on the employment, earnings, and income of persons in different demographic groups. I classify individuals by sex, education, and race. The analysis uses data from the Current Population Surveyâs Outgoing Rotation Group data, covering the period 1979â1992, and March Annual Demographic File data, covering the period 1975â1997. Many different individual and family outcome measures are considered, including employment to population ratios, weekly earnings, hourly earnings, annual hours, annual earnings, family earnings, family transfer income, and total family income. The regression model is specified such that the key parameters measure how the labor market outcomes of less-skilled workers vary with the business cycle relative to the variability for high-skill groups. The analysis uses variation across MSAs in the timing and severity of shocks. The results consistently show that individuals with lower educational levels, nonwhites, and low-skill women experience greater cyclical fluctuation than high-skill men. These results are the most striking when examining comprehensive measures of labor force activity such as the likelihood of full-time, full-year work. Government transfers and the earnings of other family members decrease the differences between groups, resulting in more skill-group-neutral effects of business cycles on family income than on individual earnings. The paper examines the stability of these results by comparing evidence across the 1982 and 1992 recessions. The evidence suggests that the 1992 recession led to more uniform effects across skill groups than did earlier cycles.
Coupled Mg/Ca and clumped isotope analyses of foraminifera provide consistent water temperatures
The reliable determination of past seawater temperature is fundamental to paleoclimate studies. We test the robustness of two paleotemperature proxies by combining Mg/Ca and clumped isotopes (Î47) on the same specimens of core top planktonic foraminifera. The strength of this approach is that Mg/Ca and Î47 are measured on the same specimens of foraminifera, thereby providing two independent estimates of temperature. This replication constitutes a rigorous test of individual methods with the advantage that the same approach can be applied to fossil specimens. Aliquots for Mg/Ca and clumped analyses are treated in the same manner following a modified cleaning procedure of foraminifera for trace element and isotopic analyses. We analysed eight species of planktonic foraminifera from coretop samples over a wide range of temperatures from 2 to 29°C. We provide a new clumped isotope temperature calibrations using subaqueous cave carbonates, which is consistent with recent studies. Tandem Mg/CaâÎ47 results follow an exponential curve as predicted by temperature calibration equations. Observed deviations from the predicted Mg/Ca-Î47 relationship are attributed to the effects of Fe-Mn oxide coatings, contamination, or dissolution of foraminiferal tests. This coupled approach provides a high degree of confidence in temperature estimates when Mg/Ca and Î47 yield concordant results, and can be used to infer the past ÎŽ18O of seawater (ÎŽ18Osw) for paleoclimate studies
Spin Structures on Kleinian Manifolds
We derive the topological obstruction to spin-Klein cobordism. This result
has implications for signature change in general relativity, and for the
superstring.Comment: 8 page
The impact of multiple interviews on the accuracy and narrative coherence of childrenâs memories
This study investigated the accuracy and narrative coherence of childrenâs accounts of a staged event across two interviews in comparison to a control condition to discern between the effects of repeated recall and delay between interviews. Seventy-six 8â11-year-olds took part in a first aid training session. Half of the children were randomly assigned to be interviewed using open-ended questions twice, one week after the event and five weeks after the event, whilst the other half were interviewed only once, five weeks after the event. Supporting the hypotheses, children reported more details over the course of two interviews than in a single interview either 1-week or 5-weeks after the event, and details that remained consistent across the two interviews were more accurate than reminisced details. The increased completeness of childrenâs accounts in two interviews was accompanied by an increase in the use of markers of causal-temporal connectedness. The hypothesis regarding the negative effect of delay on the accuracy of childrenâs testimony was partially supported, as details reported in the first, 1-week interview were more accurate than details in the single 5-week interview. Results demonstrate that multiple interviews can increase the narrative coherence of childrenâs testimony without decreasing their accuracy
Quasi-exactly solvable quartic potential
A new two-parameter family of quasi-exactly solvable quartic polynomial
potentials is introduced. Until now,
it was believed that the lowest-degree one-dimensional quasi-exactly solvable
polynomial potential is sextic. This belief is based on the assumption that the
Hamiltonian must be Hermitian. However, it has recently been discovered that
there are huge classes of non-Hermitian, -symmetric Hamiltonians
whose spectra are real, discrete, and bounded below [physics/9712001].
Replacing Hermiticity by the weaker condition of symmetry allows
for new kinds of quasi-exactly solvable theories. The spectra of this family of
quartic potentials discussed here are also real, discrete, and bounded below,
and the quasi-exact portion of the spectra consists of the lowest
eigenvalues. These eigenvalues are the roots of a th-degree polynomial.Comment: 3 Pages, RevTex, 1 Figure, encapsulated postscrip
Velocity Segregation and Systematic Biases In Velocity Dispersion Estimates With the SPT-GMOS Spectroscopic Survey
The velocity distribution of galaxies in clusters is not universal; rather,
galaxies are segregated according to their spectral type and relative
luminosity. We examine the velocity distributions of different populations of
galaxies within 89 Sunyaev Zel'dovich (SZ) selected galaxy clusters spanning . Our sample is primarily draw from the SPT-GMOS spectroscopic
survey, supplemented by additional published spectroscopy, resulting in a final
spectroscopic sample of 4148 galaxy spectra---2868 cluster members. The
velocity dispersion of star-forming cluster galaxies is % greater than
that of passive cluster galaxies, and the velocity dispersion of bright () cluster galaxies is % lower than the velocity dispersion of
our total member population. We find good agreement with simulations regarding
the shape of the relationship between the measured velocity dispersion and the
fraction of passive vs. star-forming galaxies used to measure it, but we find a
small offset between this relationship as measured in data and simulations in
which suggests that our dispersions are systematically low by as much as 3\%
relative to simulations. We argue that this offset could be interpreted as a
measurement of the effective velocity bias that describes the ratio of our
observed velocity dispersions and the intrinsic velocity dispersion of dark
matter particles in a published simulation result. Measuring velocity bias in
this way suggests that large spectroscopic surveys can improve dispersion-based
mass-observable scaling relations for cosmology even in the face of velocity
biases, by quantifying and ultimately calibrating them out.Comment: Accepted to ApJ; 21 pages, 11 figures, 5 table
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