21,387 research outputs found
Berry Curvature on the Fermi Surface: Anomalous Hall Effect as a Topological Fermi-Liquid Property
The intrinsic anomalous Hall effect in metallic ferromagnets is shown to be
controlled by Berry phases accumulated by adiabatic motion of quasiparticles on
the Fermi surface, and is purely a Fermi-liquid property, not a ``bulk'' Fermi
sea property like Landau diamagnetism, as has been previously supposed. Berry
phases are a new topological ingredient that must be added to Landau
Fermi-liquid theory in the presence of broken inversion or time-reversal
symmetry.Comment: 4 pages, 0 figures; to appear in Physical Review Letters; cleaner
form of main formula+note added confirming continued validity of result in
interacting Fermi liquids: + improved summary paragraph stating result; final
published version (minor changes
c=1 String as a Topological Model
The discrete states in the string are shown to be the physical states
of a certain topological sigma model. We define a set of new fields directly
from variables, in terms of which the BRST charge and energy-momentum
tensor are rewritten as those of the topological sigma model. Remarkably,
ground ring generator turns out to be a coordinate of the sigma model. All
of the discrete states realize a graded ring which contains ground ring as a
subset.Comment: 23 pages + 3 figures in PostScript, LaTeX, UT-Komaba/93-7.
Description of the physical spectrum in terms of topological model is
improved. Some references and new figures added. (figures are available upon
request.
Diagnóstico de doenças de peixes no laboratório de piscicultura.
bitstream/item/50984/1/Diagnostico-de-doencas-de-p..pdfSIDE 021/10 - Portal Dia de Campo, 18 maio 2010; SIDE 021/10A - Douradosnews, 12 jun. 2010; SIDE 021/10B - Jornal Correio do Estado: OpiniĂŁo, 17 maio 2010; SIDE 021/10C - Portal do AgronegĂłcio, 13 maio 2010; SIDE 021/10D - Guia da Pesca, 12 maio 2010
Geometrical Construction of Heterogeneous Loop Amplitudes in 2D Gravity
We study a disk amplitude which has a complicated heterogeneous matter
configuration on the boundary in a system of the (3,4) conformal matter coupled
to two-dimensional gravity. It is analyzed using the two-matrix chain model in
the large N limit. We show that the disk amplitude calculated by
Schwinger-Dyson equations can completely be reproduced through purely
geometrical consideration. From this result, we speculate that all
heterogeneous loop amplitudes can be derived from the geometrical consideration
and the consistency among relevant amplitudes.Comment: 13 pages, 11 figure
Four-quark final state in W-pair production: Case of signal and background
We discuss theoretical predictions for W-pair production and decay at LEP2
and higher energies in a form suitable for comparison with raw data. We present
a practical framework for calculating uncertainties of predictions given by the
KORALW and grc4f Monte Carlo programs. As an example we use observables in the
decay channel: the total four-quark (four-jet) cross section
and two-quark/jet invariant-mass distribution and cross section, in the case
when the other two may escape detection. Effects of QED bremsstrahlung,
effective couplings, running W and Z widths, Coulomb interaction and the
complete tree level set of diagrams are discussed. We also revisit the question
of technical precision of the new version 1.21 of the KORALW Monte Carlo code
as well as of version 1.2(26) of the grc4f one.
Finally we find predictions of the two programs to have an overall physical
uncertainty of 2%.
As a side result we show, on the example of an invariant mass
distribution, the strong interplay of spin correlations and detector cut-offs
in the case of four-fermion final states.Comment: 26 pages, LaTe
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