1,119 research outputs found
Experimental application of LANDSAT to geobotanical prospecting of serpentine outcrops in the central Appalachian Piedmont of North America
The use of LANDSAT as a tool for geobotanical prospecting was studied in a 13,137 sq km area from southeastern Pennsylvania to northern Virginia. Vegetation differences between known serpentine and non-sepentine sites were most easily distinguished on early summer images. A multispectral signature was derived from vegetation of two known serpentine sites and a map was produced of 159 similar signatures of vegetation in the study area. Authenticity of the serpentine nature of the mapped sites was checked via geochemical analysis of collected soils from 14% of the sites. Overall success of geobotanical prospecting was about 35% for the total study area. When vegetation distribution was taken into account, the success rate was 67% for the region north of the Potomac, demonstrates the effectiveness of the multispectral satellite for quickly and accurately locating mineral sensitive vegetation communities over vast tracts of land
On the chiral anomaly in non-Riemannian spacetimes
The translational Chern-Simons type three-form coframe torsion on a
Riemann-Cartan spacetime is related (by differentiation) to the Nieh-Yan
four-form. Following Chandia and Zanelli, two spaces with non-trivial
translational Chern-Simons forms are discussed. We then demonstrate, firstly
within the classical Einstein-Cartan-Dirac theory and secondly in the quantum
heat kernel approach to the Dirac operator, how the Nieh-Yan form surfaces in
both contexts, in contrast to what has been assumed previously.Comment: 18 pages, RevTe
On a class of invariant coframe operators with application to gravity
Let a differential 4D-manifold with a smooth coframe field be given. Consider
the operators on it that are linear in the second order derivatives or
quadratic in the first order derivatives of the coframe, both with coefficients
that depend on the coframe variables. The paper exhibits the class of operators
that are invariant under a general change of coordinates, and, also, invariant
under the global SO(1,3)-transformation of the coframe. A general class of
field equations is constructed. We display two subclasses in it. The subclass
of field equations that are derivable from action principles by free variations
and the subclass of field equations for which spherical-symmetric solutions,
Minkowskian at infinity exist. Then, for the spherical-symmetric solutions, the
resulting metric is computed. Invoking the Geodesic Postulate, we find all the
equations that are experimentally (by the 3 classical tests) indistinguishable
from Einstein field equations. This family includes, of course, also Einstein
equations. Moreover, it is shown, explicitly, how to exhibit it. The basic tool
employed in the paper is an invariant formulation reminiscent of Cartan's
structural equations. The article sheds light on the possibilities and
limitations of the coframe gravity. It may also serve as a general procedure to
derive covariant field equations
Temporal Trends in Migration in the Ă land Islands: Effects of Population Size and Geographic Distance
This is the published version. Copyright 1994 Wayne State University Press.Using a model developed by Relethford (1992), we assess temporal trends (1750-1949) in marital migration in the Aland Islands, Finland, in relation to both geographic distance and population size. The 200-year time period was divided into four 50-year periods. For all time periods both geographic distance and population size are important determinants of migration among 15 Lutheran parishes. The geographic distance parameter of the model decreases significantly over time, and the population size parameter fluctuates slightly but shows no significant change over time. For all time periods migration is negative density dependent, indicating that there is greater relative flow from larger to smaller subdivisions. Even though both the geographic distance and population size parameters are statistically significant, the analysis suggests that geographic distance has a greater relative effect on migration than population size. There is a clear indication of isolate breakdown during the last two time periods (1850-1899 and 1900-1949). Residual analysis indicated that the smallest parish (Sottunga) was a major outlier that showed greater exogamy (less endemicity) than expected from the model
Symmetric Hyperbolic System in the Self-dual Teleparallel Gravity
In order to discuss the well-posed initial value formulation of the
teleparallel gravity and apply it to numerical relativity a symmetric
hyperbolic system in the self-dual teleparallel gravity which is equivalent to
the Ashtekar formulation is posed. This system is different from the ones in
other works by that the reality condition of the spatial metric is included in
the symmetric hyperbolicity and then is no longer an independent condition. In
addition the constraint equations of this system are rather simpler than the
ones in other works.Comment: 8 pages, no figure
Metallic ferromagnetism: Progress in our understanding of an old strong-coupling problem
Metallic ferromagnetism is in general an intermediate to strong coupling
phenomenon. Since there do not exist systematic analytic methods to investigate
such types of problems, the microscopic origin of metallic ferromagnetism is
still not sufficiently understood. However, during the last two or three years
remarkable progress was made in this field: It is now certain that even in the
one-band Hubbard model metallic ferromagnetism is stable in dimensions
2, and on regular lattices and at intermediate values of the
interaction and density . In this paper the basic questions and recent
insights regarding the microscopic conditions favoring metallic ferromagnetism
in this model are reviewed. These findings are contrasted with the results for
the orbitally degenerate case.Comment: 16 pages, 13 figures, latex using vieweg.sty (enclosed); typos
corrected; to appear in "Advances in Solid State Physics", Vol. 3
Hidden Consequence of Active Local Lorentz Invariance
In this paper we investigate a hidden consequence of the hypothesis that
Lagrangians and field equations must be invariant under active local Lorentz
transformations. We show that this hypothesis implies in an equivalence between
spacetime structures with several curvature and torsion possibilities.Comment: Some misprints appearing in the published version have been correcte
- âŠ