3,383 research outputs found
On leading spiral arms in close pairs of galaxies
It is explained why one can observe a leading spiral pattern in close pairs of galaxies where the direction of the orbital momentum of the satellite is opposite to the direction of the spin of the spiral galaxy
Tropospheric limitations on the accuracy of phase measurement of coordinates in astronomy
The effect of tropospheric fluctuation on the accuracy of phase measurements of coordinates is discussed. The nature of the averaging of the tropospheric effects, if N coordinate measurements of duration T with period mu are made, is investigated. Various averaging modes depending on the relation of the various time parameters are investigated. Equations taking into account the correlations between individual observations are presented. It is shown that the correlation interval between the individual observations is always greater than the fluctuation period of tropospheric inhomogeneities typical for a given baseline
Phase locking of coupled lasers with many longitudinal modes
Detailed experimental and theoretical investigations on two coupled fiber
lasers, each with many longitudinal modes, reveal that the behavior of the
longitudinal modes depends on both the coupling strength as well as the
detuning between them. For low to moderate coupling strength only longitudinal
modes which are common for both lasers phase-lock while those that are not
common gradually disappear. For larger coupling strengths, the longitudinal
modes that are not common reappear and phase-lock. When the coupling strength
approaches unity the coupled lasers behave as a single long cavity with
correspondingly denser longitudinal modes. Finally, we show that the gradual
increase in phase-locking as a function of the coupling strength results from
competition between phase-locked and non phase-locked longitudinal modes.Comment: 3 pages, 4 figures, submitted to opt. let
Lateral imaging of the superconducting vortex lattice using Doppler-modulated scanning tunneling microscopy
By spatially mapping the Doppler effect of an in-plane magnetic field on the
quasiparticle tunneling spectrum, we have laterally imaged the vortex lattice
in superconducting 2H-NbSe2. Cryomagnetic scanning tunneling spectroscopy was
performed at 300 mK on the ab-surface oriented parallel to the field H.
Conductance images at zero bias show stripe patterns running along H, with the
stripe separation varying as H^-0.5. Regions of higher zero-bias conductance
show lower gap-edge conductance, consistent with spectral redistribution by
spatially-modulated superfluid momentum. Our results are interpreted in terms
of the interaction between vortical and screening currents, and demonstrate a
general method for probing subsurface vortices.Comment: 3 pages, 3 figures, to appear in Applied Physics Letter
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