4,145 research outputs found
Interplay of charge and spin correlations in nickel perovskites
Analyzing the motion of low--spin holes in a high--spin
background, we derive a sort of generalized t--J Hamiltonian for the planes of Sr--doped nickelates. In addition to the rather complex
carrier--spin and spin--spin couplings we take into account the coupling of the
doped holes to in--plane oxygen breathing modes by a Holstein--type interaction
term. Because of strong magnetic confinement effects the holes are nearly
entirely prelocalized and the electron--phonon coupling becomes much more
effective in forming polarons than in the isostructural cuprates. In the light
of recent experiments on we discuss how the variety of
the observed transport and charge/spin--ordering phenomena can be qualitatively
understood in terms of our model Hamiltonian.Comment: 2 pages, LTpaper.sty, Proc. XXI Int. Conf. on Low Temp. Phys. Prague
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Conjugacy classes of p-cycles of type D in alternating groups
We classify the conjugacy classes of p-cycles of type D in alternating
groups. This finishes the open cases in arXiv:0812.4628. We also determine all
the subracks of those conjugacy classes which are not of type D.Comment: Second paragraph of subsection 2.2 rewritten. 4-th sentence of
subsection 2.4 rewritten. More explanations added in Remark 2.4. Lemma 2.5
and Corollary 2.7 added. Appendix removed and put it as Remark 3.1. Remark
3.2 (former 3.1) reorganized. References: [Da], [EGSS], [H], [IS] added,
[GPPS] removed. Communications in Algebra (2014
Resonant Inelastic X-Ray Scattering from Valence Excitations in Insulating Copper-Oxides
We report resonant inelastic x-ray measurements of insulating LaCuO
and SrCuOCl taken with the incident energy tuned near the Cu K
absorption edge. We show that the spectra are well described in a shakeup
picture in 3rd order perturbation theory which exhibits both incoming and
outgoing resonances, and demonstrate how to extract a spectral function from
the raw data. We conclude by showing {\bf q}-dependent measurements of the
charge transfer gap.Comment: minor notational changes, discussion of anderson impurity model
fixed, references added; accepted by PR
Ab initio calculations of the hydrogen bond
Recent x-ray Compton scattering experiments in ice have provided useful
information about the quantum nature of the interaction between HO
monomers. The hydrogen bond is characterized by a certain amount of charge
transfer which could be determined in a Compton experiment. We use ab-initio
simulations to investigate the hydrogen bond in HO structures by
calculating the Compton profile and related quantities in three different
systems, namely the water dimer, a cluster containing 12 water molecules and
the ice crystal. We show how to extract estimates of the charge transfer from
the Compton profiles.Comment: 16 pages, 7 figures, to appear in Phys. Rev.
Knowledge Cartography for Controversies: The Iraq Debate
In analysing controversies and debates—which would include reviewing a literature in order to plan research, or assessing intelligence to formulate policy—there is no one worldview which can be mapped, for instance as a single, coherent concept map. The cartographic challenge is to show which facts are agreed and contested, and the different kinds of narrative links that use facts as evidence to define the nature of the problem, what to do about it, and why. We will use the debate around the invasion of Iraq to demonstrate the methodology of using a knowledge mapping tool to extract key ideas from source materials, in order to classify and connect them within and across a set of perspectives of interest to the analyst. We reflect on the value that this approach adds, and how it relates to other argument mapping approaches
Observing the Symmetry of Attractors
We show how the symmetry of attractors of equivariant dynamical systems can
be observed by equivariant projections of the phase space. Equivariant
projections have long been used, but they can give misleading results if used
improperly and have been considered untrustworthy. We find conditions under
which an equivariant projection generically shows the correct symmetry of the
attractor.Comment: 28 page LaTeX document with 9 ps figures included. Supplementary
color figures available at http://odin.math.nau.edu/~jws
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