5,290 research outputs found
Bifurcation of gap solitons through catastrophe theory
In the theory of optical gap solitons, slowly-moving finite-amplitude
Lorentzian solutions are found to mediate the transition from bright to
coexistent dark-antidark solitary wave pairs when the laser frequency is
detuned out of the proper edge of a dynamical photonic bandgap. Catastrophe
theory is applied to give a geometrical description of this strongly
asymmetrical 'morphing' process.Comment: 6 pages, 3 figures, submitted to Phys. Rev.
Mechanism of wave breaking from a vacuum point in the defocusing nonlinear Schrödinger equation
We study the wave breaking mechanism for the weakly dispersive defocusing nonlinear Schrödinger equation with a constant phase dark initial datum that contains a vacuum point at the origin. We prove by means of the exact solution to the initial value problem that, in the dispersionless limit, the vacuum point is preserved by the dynamics until breaking occurs at a finite critical time. In particular, both Riemann invariants experience a simultaneous breaking at the origin. Although the initial vacuum point is no longer preserved in the presence of a finite dispersion, the critical behavior manifests itself through an abrupt transition occurring around the breaking time
Resonant radiation shed by dispersive shock waves
We show that dispersive shock waves resulting from the nonlinearity
overbalancing a weak leading-order dispersion can emit resonant radiation owing
to higher-order dispersive contributions. We analyze such phenomenon for the
defocusing nonlinear Schroedinger equation, giving criteria for calculating the
radiated frequency based on the estimate of the shock velocity, revealing also
a diversity of possible scenarios depending on the order and magnitude of the
dispersive corrections
Time-reversal focusing of an expanding soliton gas in disordered replicas
We investigate the properties of time reversibility of a soliton gas,
originating from a dispersive regularization of a shock wave, as it propagates
in a strongly disordered environment. An original approach combining
information measures and spin glass theory shows that time reversal focusing
occurs for different replicas of the disorder in forward and backward
propagation, provided the disorder varies on a length scale much shorter than
the width of the soliton constituents. The analysis is performed by starting
from a new class of reflectionless potentials, which describe the most general
form of an expanding soliton gas of the defocusing nonlinear Schroedinger
equation.Comment: 7 Pages, 6 Figure
The real exchange rate process and its real effects: The cases of Mexico and the USA
Exchange rate management is a salient macroeconomic issue, especially in developing countries. In this paper, we study political economy factors that may affect the real exchange rate (RER) process and the real economic effects of the RER. We review recent literature on the effects of elections on the exchange rate, and adapt Ball’s (1992) model to show that uncertainty about the future course of policy may make more appreciated RER’s less predictable. We also review the literature on the real effect of RER appreciations and of RER uncertainty. We then construct a simultaneous GARCH-M model of the joint determination of the RER and output capable of testing our hypotheses simultaneously in a single model. We estimate the model using data first from Mexico, a developing country, and the US. In Mexico we find that elections significantly affect the evolution of the RER, that more appreciated RERs are less predictable, that RER depreciations lower output growth and that RER uncertainty lowers output growth, even when controlling for its wellstudied effect on trade. By contrast, none of these effects are found in the US data.real exchange rate volatility, economic growth, electoral cycle
A collective modulation instability of multiple four-wave mixing
We investigate the modulation instability of multiple four-wave mixing
arising from a dual-frequency pump in a single-mode fiber or waveguide. By
applying the Floquet theory on account of the periodic nature of four-wave
mixing, we reveal a collective type of instability occurring in the anomalous
dispersion regime. Our interpretation of the linear stability analysis is
validated by the numerical solution of the nonlinear Schroedinger equationComment: 4 pages, 3 figure
Shocks in nonlocal media
We investigate the formation of collisionless shocks along the spatial
profile of a gaussian laser beam propagating in nonlocal nonlinear media. For
defocusing nonlinearity the shock survives the smoothing effect of the nonlocal
response, though its dynamics is qualitatively affected by the latter, whereas
for focusing nonlinearity it dominates over filamentation. The patterns
observed in a thermal defocusing medium are interpreted in the framework of our
theory.Comment: 5 pages, 5 figure
Modulational instability in dispersion oscillating fiber ring cavities
We show that the use of a dispersion oscillating fiber in passive cavities
significantly extend modulational instability to novel high-frequency bands,
which also destabilize the branches of the steady response which are stable
with homogeneous dispersion. By means of Floquet theory, we obtain exact
explicit expression for the sideband gain, and a simple analytical estimate for
the frequencies of maximum gain. Numerical simulations show that stable
stationary trains of pulses can be excited in the cavity
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