16,462 research outputs found
The importance of local band effects for ferromagnetism in hole doped LaCuO
Band calculations for supercells of LaBaCuO show that the
rigid band model for doping is less adequate than what is commonly assumed. In
particular, weak ferromagnetism (FM) can appear locally around clusters of high
Ba concentration. The clustering is important at large dilution and averaged
models for magnetism, such as the virtual crystal approximation, are unable to
stabilize magnetic moments. These results give a support to the idea that weak
FM can be the cause of the destruction of superconductivity at high hole
doping.Comment: 4 pages, 5 figures, accepted for publication in Physical Review
Letter
Remote sensing in Iowa agriculture
The author has identified the following significant results. Analysis of 1972 single-date coverage indicated that a complete crop classification was not attainable at the test sites. Good multi-date coverage during 1973 indicates that many of the problems encountered in 1972 will be minimized. In addition, the compilation of springtime imagery covering the entire state of Iowa has added a new dimension to interpretation of Iowa's natural resources. ERTS-1 has provided data necessary to achieve the broad synoptic view not attainable through other means. This should provide soils and crop researchers and land use planners a base map of Iowa. Granted and due to the resolution of ERTS-1, not all details are observable for many land use planning needs, but this gives a general and current view of Iowa
A pure S-wave covariant model for the nucleon
Using the manifestly covariant spectator theory, and modeling the nucleon as
a system of three constituent quarks with their own electromagnetic structure,
we show that all four nucleon electromagnetic form factors can be very well
described by a manifestly covariant nucleon wave function with zero orbital
angular momentum. Since the concept of wave function depends on the formalism,
the conclusions of light-cone theory requiring nonzero angular momentum
components are not inconsistent with our results. We also show that our model
gives a qualitatively correct description of deep inelastic scattering,
unifying the phenomenology at high and low momentum transfer. Finally we review
two different definitions of nuclear shape and show that the nucleon is
spherical in this model, regardless of how shape is defined.Comment: 20 pages and 10 figures; greatly expanded version with new fits and
discussion of DIS; similar to published versio
Remote sensing in Iowa agriculture: Identification and classification of Iowa's crops, soils and forestry resources using ERTS-1 and complimentary underflight imagery
The author has identified the following significant results. Springtime ERTS-1 imagery covering pre-selected test sites in Iowa showed considerable detail with respect to broad soil and land use patterns. Additional imagery has been incorporated into a state mosaic. The mosaic was used as a base for soil association lines transferred from an existing map. The regions of greatest contrast are between the Clarion-Nicollet-Webster soil association area and adjacent areas. Landscape characteristics in this area result in land use patterns with a high percentage of pasture, hay, and timber. The soil association areas of the state that have patterns interpreted to be associated with intensive row crop production are: Moody, Galva-Primghar-Sac, Clarion-Nicollet-Webter, Tama-Muscatine, Dinsdale-Tama, Cresco-Lourdes, Clyde, Kenyon-Floyd-Clyde, and the Luton-Onawa-Salix area on the Missouri River floodplain. Forestland estimates have been attained for an area in central Iowa using wintertime ERTS-1 imagery. Visual analysis of multispectral, temporal imagery indicates that temporal analysis for cropland identification and acreage analyses procedures may be a very useful tool. Combinations of wintertime, springtime, and summertime ERTS-1 imagery separate most vegetation types. Timing can be critical depending upon crop development and harvesting times because of the dynamic nature of agricultural production
Inclusive Breakup Theory of Three-Body Halos
We present a recently developed theory for the inclusive breakup of
three-fragment projectiles within a four-body spectator model
\cite{CarPLB2017}, for the treatment of the elastic and inclusive non-elastic
break up reactions involving weakly bound three-cluster nuclei in
/ collisions. The four-body theory is an extension of the
three-body approaches developed in the 80's by Ichimura, Autern and Vincent
(IAV) \cite{IAV1985}, Udagawa and Tamura (UT) \cite{UT1981} and Hussein and
McVoy (HM) \cite{HM1985}. We expect that experimentalists shall be encouraged
to search for more information about the system in the elastic
breakup cross section and that also further developments and extensions of the
surrogate method will be pursued, based on the inclusive non-elastic breakup
part of the spectrum.Comment: 8 pages, 3 figures, Contribution to the Proceedings of Fusion17:
"International Conference on Heavy-Ion Collisions at Near-Barrier Energies",
20-24 February 2017 Hobart, Tasmania, Australi
Disorder Effects in Fluctuating One-Dimensional Interacting Systems
The zero temperature localization of interacting electrons coupled to a
two-dimensional quenched random potential, and constrained to move on a
fluctuating one-dimensional string embedded in the disordered plane, is studied
using a perturbative renormalization group approach. In the reference frame of
the electrons the impurities are dynamical and their localizing effect is
expected to decrease. We consider several models for the string dynamics and
find that while the extent of the delocalized regime indeed grows with the
degree of string fluctuations, the critical interaction strength, which
determines the localization-delocalization transition for infinitesimal
disorder,does not change unless the fluctuations are softer than those of a
simple elastic string.Comment: 15 page
Remote sensing in Iowa agriculture: Identification and classification of Iowa's crops, soils and forestry resources using ERTS-1 and complimentary underflight imagery
There are no author-identified significant results in this report
Scaling and Duality in Semi-exclusive Processes
We discuss extending scaling and duality studies to semi-exclusive processes.
We show that semi-exclusive hard pion photoproduction should exhibit scaling
behavior in kinematic regions where the photon and pion both interact directly
with the same quark. We show that such kinematic regions exist. We also show
that the constancy with changing momentum transfer of the resonance
peak/scaling curve ratio, familiar for many resonances in deep inelastic
scattering, is also expected in the semi-exclusive case.Comment: 8 pages, 4 figures, submitted to Phys.Rev.
Large N_c, Constituent Quarks, and N, Delta Charge Radii
We show how one may define baryon constituent quarks in a rigorous manner,
given physical assumptions that hold in the large-N_c limit of QCD. This
constituent picture gives rise to an operator expansion that has been used to
study large-N_c baryon observables; here we apply it to the case of charge
radii of the N and Delta states, using minimal dynamical assumptions. For
example, one finds the relation r_p^2 - r_{Delta^+}^2 = r_n^2 - r_{Delta^0}^2
to be broken only by three-body, O(1/N_c^2) effects for any N_c.Comment: 15 pages, 1 eps figure. Version to appear in Phys. Rev.
Neel order, quantum spin liquids and quantum criticality in two dimensions
This paper is concerned with the possibility of a direct second order
transition out of a collinear Neel phase to a paramagnetic spin liquid in two
dimensional quantum antiferromagnets. Contrary to conventional wisdom, we show
that such second order quantum transitions can potentially occur to certain
spin liquid states popular in theories of the cuprates. We provide a theory of
this transition and study its universal properties in an expansion.
The existence of such a transition has a number of interesting implications for
spin liquid based approaches to the underdoped cuprates. In particular it
considerably clarifies existing ideas for incorporating antiferromagnetic long
range order into such a spin liquid based approach.Comment: 18 pages, 17 figure
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