4,937 research outputs found
Mode structure and ray dynamics of a parabolic dome microcavity
We consider the wave and ray dynamics of the electromagnetic field in a
parabolic dome microcavity. The structure of the fundamental s-wave involves a
main lobe in which the electromagnetic field is confined around the focal point
in an effective volume of the order of a cubic wavelength, while the modes with
finite angular momentum have a structure that avoids the focal area and have
correspondingly larger effective volume. The ray dynamics indicates that the
fundamental s-wave is robust with respect to small geometrical deformations of
the cavity, while the higher order modes are associated with ray chaos and
short-lived. We discuss the incidence of these results on the modification of
the spontaneous emission dynamics of an emitter placed in such a parabolic dome
microcavity.Comment: 50 pages, 17 figure
Separation and acceleration of analogues of magnetic monopoles in semiconductor microcavities
Half-integer topological defects in polariton condensates can be regarded as
magnetic charges, with respect to built-in effective magnetic fields present in
microcavities. We show how an integer topological defect can be separated into
a pair of half-integer ones, paving the way towards flows of magnetic charges:
spin currents or magnetricity. We discuss the corresponding experimental
implementation within microwires (with half-solitons) and planar microcavities
(with half-vortices).Comment: 18 Pages, 8 figures, submitted to New Journal of Physics (special
issue
A rapid evolving region in the Galactic Center: Why S-stars thermalize and more massive stars are missing
The existence of "S-stars" within a distance of 1" from SgrA contradicts
our understanding of star formation, due to the forbiddingly violent
environment. A suggested possibility is that they form far and have been
brought in by some fast dynamical process, since they are young. Nonetheless,
all conjectured mechanisms either fail to reproduce their eccentricities
--without violating their young age-- or cannot explain the problem of "inverse
mass segregation": The fact that lighter stars (the S-stars) are closer to
SgrA and more massive ones, Wolf-Rayet (WR) and O-stars, are farther out.
In this Letter we propose that the responsible for both, the distribution of
the eccentricities and the paucity of massive stars, is the Kozai-Lidov-{\em
like} resonance induced by a sub-parsec disk recently discovered in the
Galactic center. Considering that the disk probably extended to smaller radius
in the past, we show that in as short as (a few) years, the stars
populating the innermost 1" region would redistribute in angular-momentum space
and recover the observed "super-thermal" distribution. Meanwhile, WR and
O-stars in the same region intermittently attain ample eccentricities that will
lead to their tidal disruptions by the central massive black hole. Our results
provide new evidences that SgrA was powered several millions years ago by
an accretion disk as well as by tidal stellar disruptions.Comment: 5 pages, two figures, accepted for publication ApJ Lett
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