1,544 research outputs found
Experimental control of pattern formation by photonic lattices
We study the control of modulational instability and pattern formation in a nonlinear dissipative feedback
system with a periodic modulation of the material refractive index. We use a one-dimensional photonic lattice
in a single-mirror feedback configuration and identify three mechanisms for pattern control: bandgap
suppression of instability modes, periodicity induced pattern modes, and orientational pattern control.The authors acknowledge the support of the
Conseil Régional de Lorraine, the bilateral FrenchAustralian
Science and Technology program, and the
Australian Research Council through Discovery
projects
Monitoring ultrashort pulses by transverse frequency doubling of counterpropagating pulses in random media
The authors study experimentally the transverse second-harmonic generation of counterpropagating pulses by a quasi-phase-matching in a medium with a random ferroelectric domain structure. The authors show that this parametric process results in a direct realization of the cross correlation of two optical signals and, therefore, it can be employed for direct characterizations of ultrashort pulses including their temporal structure and pulse front tilt.The authors acknowledge the support of the Australian
Research Council
Universal subspaces for compact Lie groups
For a representation of a connected compact Lie group G in a finite
dimensional real vector space U and a subspace V of U, invariant under a
maximal torus of G, we obtain a sufficient condition for V to meet all G-orbits
in U, which is also necessary in certain cases. The proof makes use of the
cohomology of flag manifolds and the invariant theory of Weyl groups. Then we
apply our condition to the conjugation representations of U(n), Sp(n), and
SO(n) in the space of matrices over C, H, and R, respectively. In
particular, we obtain an interesting generalization of Schur's
triangularization theorem.Comment: 20 page
Yang-Mills fields on CR manifolds
We study pseudo Yang-Mills fields on a compact strictly pseudoconvex CR
manifold.Comment: 52 page
Some Grüss' Type Inequalities in 2-Inner Product Spaces and Applications for Determinantal Integral Inequalities
Some new Grüss type inequalities in 2-inner product spaces are given. Using this framework, some determinantal integral inequalities for synchronous functions are also derived
An HST/STIS Optical Transmission Spectrum of Warm Neptune GJ 436b
GJ 436b is a prime target for understanding warm Neptune exoplanet
atmospheres and a target for multiple JWST GTO programs. Here, we report the
first space-based optical transmission spectrum of the planet using two
HST/STIS transit observations from 0.53-1.03 microns. We find no evidence for
alkali absorption features, nor evidence of a scattering slope longward of 0.53
microns. The spectrum is indicative of moderate to high metallicity (~100-1000x
solar) while moderate metallicity scenarios (~100x solar) require aerosol
opacity. The optical spectrum also rules out some highly scattering haze
models. We find an increase in transit depth around 0.8 microns in the
transmission spectra of 3 different sub-Jovian exoplanets (GJ 436b, HAT-P-26b,
and GJ 1214b). While most of the data come from STIS, data from three other
instruments may indicate this is not an instrumental effect. Only the transit
spectrum of GJ 1214b is well fit by a model with stellar plages on the
photosphere of the host star. Our photometric monitoring of the host star
reveals a stellar rotation rate of 44.1 days and an activity cycle of 7.4
years. Intriguingly, GJ 436 does not become redder as it gets dimmer, which is
expected if star spots were dominating the variability. These insights into the
nature of the GJ 436 system help refine our expectations for future
observations in the era of JWST, whose higher precision and broader wavelength
coverage will shed light on the composition and structure of GJ 436b's
atmosphere.Comment: 20 pages, 11 figures, 5 tables, Accepted to AJ. A full version of
table 1 is included as table1_mrt.tx
Trapezoidal type inequalities related to h-convex functions with applications
A mapping M(t) is considered to obtain some preliminary results and a new
trapezoidal form of Fejer inequality related to the h-convex functions.
Furthermore the obtained results are applied to achieve some new inequalities
in connection with special means, random variable and trapezoidal formula
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