986 research outputs found
Aharonov-Bohm effect for excitons in a semiconductor quantum ring dressed by circularly polarized light
We show theoretically that the strong coupling of circularly polarized
photons to an exciton in ring-like semiconductor nanostructures results in
physical nonequivalence of clockwise and counterclockwise exciton rotations in
the ring. As a consequence, the stationary energy splitting of exciton states
corresponding to these mutually opposite rotations appears. This excitonic
Aharonov-Bohm effect depends on the intensity and frequency of the circularly
polarized field and can be detected in state-of-the-art optical experiments.Comment: Published versio
All-to-all connected networks by multi-frequency excitation of polaritons
We analyze theoretically a network of all-to-all coupled polariton modes,
realized by a trapped polariton condensate excited by a comb of different
frequencies. In the low-density regime the system dynamically finds a state
with maximal gain defined by the average intensities (weights) of the
excitation beams, analogous to active mode locking in lasers, and thus solves a
maximum eigenvalue problem set by the matrix of weights. The method opens the
possibility to tailor a superposition of populated bosonic modes in the trapped
condensate by appropriate choice of drive
Vortices in spinor cold exciton condensates with spin-orbit interaction
We study theoretically the ground states of topological defects in a spinor
four-component condensate of cold indirect excitons. We analyze possible ground
state solutions for different configurations of vortices and half-vortices. We
show that if only Rashba or Dreselhaus spin-orbit interaction (SOI) for
electrons is present the stable states of topological defects can represent a
cylindrically symmetric half-vortex or half vortex-antivortex pairs, or a
non-trivial pattern with warped vortices. In the presence of both of Rashba and
Dresselhaus SOI the ground state of a condensate represents a stripe phase and
vortex type solutions become unstable
Information processing with topologically protected vortex memories in exciton-polariton condensates
We show that in a non-equilibrium system of an exciton-polariton condensate,
where polaritons are generated from incoherent pumping, a ring-shaped pump
allows for stationary vortex memory elements of topological charge or
. Using simple potential guides we can choose whether to copy the same
charge or invert it onto another spatially separate ring pump. Such
manipulation of binary information opens the possibility of a new type
processing using vortices as topologically protected memory components
Surface deformation of the Krafla Fissure Swarm in two rifting events
The Krafla rifting episode in North Iceland has had 11 main tectonic events during the period December 1975 to May 1979. Each event has lasted from a few hours to several weeks. The first and eighth events affected to some extent the same part of the Krafla fissure swarm. These two tectonic events in the fissure swarm were characterized by down-faulting of a central area of the fissure swarm about 5-km-wide E-W and 20-km-long N-S. The resulting graben was boarded on both sides by an intensely faulted and fractured zone. These fracture zones showed spreading of 1.5 m in the first event and 2.66 m in the eighth one along the same reach. Elastic contraction on both sides of the fissure swarm added up to 1.4 m in the eighth event. The graben floor is estimated to have subsided about 1 m in the first event while a further subsidence of 1.1 m was observed in the 8th event. The flanks of the graben rose about 0.5 m during the latter event. The rise diminished away from the fissure swarm.
ARK: https://n2t.net/ark:/88439/y080508
Permalink: https://geophysicsjournal.com/article/83
 
Models of Cuspy Triaxial Galaxies
We construct numerical models of mildly triaxial elliptical galaxies with
central density cusps. Using a technique we call ``adiabatic squeezing'', we
begin with a spherical gamma=1 Hernquist model and apply a drag to the
velocities of the particles along each principle axis. The final models are
stable in isolation, preserving their density structure and figure shape over
many dynamical timescales. The density profile and axial ratios compare well to
the observed properties of elliptical galaxies. The orbital structure of these
models show a mixture of tubes, boxes, and boxlets, as expected for triaxial
systems, with very few chaotic orbits. These N-body realizations of cuspy
triaxial galaxies provide a basis for the study of the dynamical evolution of
elliptical galaxies.Comment: 14 pages, 7 figures. Accepted by Ap
A Search for Cold Dust around Neutron Stars
We present observations of nine radio pulsars using the
Heinrich-Hertz-Telescope at \lambda 0.87mm and the IRAM 30-m telescope at
\lambda 1.2mm in search for a cold dust around these sources. Five of the
program pulsars have been observed for the first time at the mm-wavelengths.
The results are consistent with the absence of circumpulsar disks that would be
massive enough () to support planet formation according to
the scenarios envisioned for solar-type stars, but they do not exclude lower
mass () disks for a wide range of grain sizes. These
conclusions confirm the previously published results and, together with the
current lack of further detections of pulsar planets, they suggest that planet
formation around neutron stars is not a common phenomenon.Comment: 5 pages, 1 figure, accepted for publication in A&
Loss cone: past, present and future
The capture and subsequent in--spiral of compact stellar remnants by central
massive black holes, is one of the more interesting likely sources of
gravitational radiation detectable by LISA. The relevant stellar population
includes stellar mass black holes, and possibly intermediate mass black holes,
generally on initially eccentric orbits. Predicted detectable rates of capture
are highly uncertain, but may be high enough that source confusion is an issue.
Foreground events with relatively high signal-to-noise ratio may provide
important tests of general relativity. I review the rate estimates in the
literature, and the apparent discrepancy between different authors' estimates,
and discuss some of the relevant uncertainties and physical processes. The
white dwarf mergers rate are uncertain by a factor of few; the neutron star
merger rate is completely uncertain and likely to be small; the black hole
merger rate is likely to be dominant for detectable mergers and is uncertain by
at least two orders of magnitude, largely due to unknown physical conditions
and processes. The primary difference in rate estimates is due to different
initial conditions and less directly due to different estimates of key physical
processes, assumed in different model scenarios for in-spiral and capture.Comment: 7 pages, revtex twocolumn, Special LISA Issue Classical and Quantum
Gravity in pres
The Evolution of Cuspy Triaxial Galaxies Harboring Central Black Holes
We use numerical simulations to study the evolution of triaxial elliptical
galaxies with central black holes. In contrast to earlier numerical studies
which used galaxy models with central density ``cores,'' our galaxies have
steep central cusps, like those observed in real ellipticals. As a black hole
grows in these cuspy triaxial galaxies, the inner regions become rounder owing
to chaos induced in the orbit families which populate the model. At larger
radii, however, the models maintain their triaxiality, and orbital analyses
show that centrophilic orbits there resist stochasticity over many dynamical
times. While black hole induced evolution is strong in the inner regions of
these galaxies, and reaches out beyond the nominal ``sphere of influence'' of a
black hole, our simulations do not show evidence for a rapid {\it global}
transformation of the host. The triaxiality of observed elliptical galaxies is
therefore not inconsistent with the presence of supermassive black holes at
their centers.Comment: 15 pages, 7 figures (1 color). Accepted for publication in Ap
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