11,190 research outputs found
Managing fisheries in a changing climate
No need to wait for more information: industrialized fishing is already wiping out stocks
Moving Embedded Solitons
The first theoretical results are reported predicting {\em moving} solitons
residing inside ({\it embedded} into) the continuous spectrum of radiation
modes. The model taken is a Bragg-grating medium with Kerr nonlinearity and
additional second-derivative (wave) terms. The moving embedded solitons (ESs)
are doubly isolated (of codimension 2), but, nevertheless, structurally stable.
Like quiescent ESs, moving ESs are argued to be stable to linear approximation,
and {\it semi}-stable nonlinearly. Estimates show that moving ESs may be
experimentally observed as 10 fs pulses with velocity th that
of light.Comment: 9 pages 2 figure
Embedded Solitons in a Three-Wave System
We report a rich spectrum of isolated solitons residing inside ({\it embedded
} into) the continuous radiation spectrum in a simple model of three-wave
spatial interaction in a second-harmonic-generating planar optical waveguide
equipped with a quasi-one-dimensional Bragg grating. An infinite sequence of
fundamental embedded solitons are found, which differ by the number of internal
oscillations. Branches of these zero-walkoff spatial solitons give rise,
through bifurcations, to several secondary branches of walking solitons. The
structure of the bifurcating branches suggests a multistable configuration of
spatial optical solitons, which may find straightforward applications for
all-optical switching.Comment: 5 pages 5 figures. To appear in Phys Rev
Relaxation effect and radiative corrections in many-electron atoms
We illuminate the importance of a self-consistent many-body treatment in
calculations of vacuum polarization corrections to the energies of atomic
orbitals in many-electron atoms. Including vacuum polarization in the atomic
Hamiltonian causes a substantial re-adjustment (relaxation) of the
electrostatic self-consistent field. The induced change in the electrostatic
energies is substantial for states with the orbital angular momentum l &;gt;
0. For such orbitals, the relaxation mechanism determines the sign and even
the order of magnitude of the total vacuum polarization correction. This
relaxation mechanism is illustrated with numerical results for the Cs atom
DOES THE CFTC COMMITMENTS OF TRADERS REPORT CONTAIN USEFUL INFORMATION?
The Commodity Futures Trading Commission's Commitments of Traders data are examined. Non-commercial positions are thought to contain the least amount of measurement error. Although non-commercials comprise a relatively small percent of the tested markets' open interest (10% to 22%), they have the most volatile net positions. The data demonstrates a statistically (positive) negative contemporaneous correlation between net positions held by (non) commercials and market returns. However, traders' net positions do not lead (Granger cause) market returns. In fact, returns lead traders' net positions. Positive returns result in an (increase) decrease in (non) commercials net positions the following week. The findings suggest that prior empirical results, which make assumptions about traders' positions not changing over a reporting interval, may be biased toward reflecting the contemporaneous position-return correlations reported in this research.Commitments of Traders, commercial traders, non-commercial traders, funds, Marketing,
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