9,410 research outputs found
The structures underlying soliton solutions in integrable hierarchies
We point out that a common feature of integrable hierarchies presenting
soliton solutions is the existence of some special ``vacuum solutions'' such
that the Lax operators evaluated on them, lie in some abelian subalgebra of the
associated Kac-Moody algebra. The soliton solutions are constructed out of
those ``vacuum solitons'' by the dressing transformation procedure.Comment: Talk given at the I Latin American Symposium on High Energy Physics,
I SILAFAE, Merida, Mexico, November/96, 5 pages, LaTeX, needs aipproc.tex,
aipproc.sty, aipproc.cls, available from
ftp://ftp.aip.org/ems/tex/macros/proceedings/6x9
Electrical conductivity measured in atomic carbon chains
The first electrical conductivity measurements of monoatomic carbon chains
are reported in this study. The chains were obtained by unraveling carbon atoms
from graphene ribbons while an electrical current flowed through the ribbon
and, successively, through the chain. The formation of the chains was
accompanied by a characteristic drop in the electrical conductivity. The
conductivity of carbon chains was much lower than previously predicted for
ideal chains. First-principles calculations using both density functional and
many-body perturbation theory show that strain in the chains determines the
conductivity in a decisive way. Indeed, carbon chains are always under varying
non-zero strain that transforms its atomic structure from cumulene to polyyne
configuration, thus inducing a tunable band gap. The modified electronic
structure and the characteristics of the contact to the graphitic periphery
explain the low conductivity of the locally constrained carbon chain.Comment: 21 pages, 9 figure
Ultrafast-pulse diagnostic using third-order frequency-resolved optical gating in organic films
We report on the diagnostic of ultrafast pulses by frequency-resolved optical gating (FROG) based on strong third-harmonic generation (THG) in amorphous organic thin films. The high THG conversion efficiency of these films allows for the characterization of sub-nanojoule short pulses emitting at telecommunication wavelengths using a low cost portable fiber spectrometer
Guidance, flight mechanics and trajectory optimization. Volume 6 - The N-body problem and special perturbation techniques
Analytical formulations and numerical integration methods for many body problem and special perturbative technique
Third-order optical autocorrelator for time-domain operation at telecommunication wavelengths
We report on amorphous organic thin films that exhibit efficient third-harmonic generation at telecommunication wavelengths. At 1550 nm, micrometer-thick samples generate up to 17 µW of green light with input power of 250 mW delivered by an optical parametric oscillator. This high conversion efficiency is achieved without phase matching or cascading of quadratic nonlinear effects. With these films, we demonstrate a low-cost, sensitive third-order autocorrelator that can be used in the time-frequency domain
Evidence for precession of the isolated neutron star RX J0720.4-3125
The XMM-Newton spectra of the isolated neutron star RX J0720.4-3125 obtained
over 4.5 years can be described by sinusoidal variations in the inferred
blackbody temperature, the size of the emitting area and the depth of the
absorption line with a period of 7.1 +/- 0.5 years, which we suggest to be the
precession period of the neutron star. Precession of a neutron star with two
hot spots of different temperature and size, probably not located exactly in
antipodal positions, may account for the variations in the X-ray spectra,
changes in the pulsed fraction, shape of the light curve and the phase-lag
between soft and hard energy bands observed from RX J0720.4-3125. An
independent sinusoidal fit to published and new pulse timing residuals from a
coherent analysis covering ~12 years yields a consistent period of 7.7 +/- 0.6
years supporting the precession model.Comment: Accepted for publication in A&A Letters, 5 pages, 5 figure
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