44,454 research outputs found
Eddington limited starbursts in the central 10pc of AGN, and the Torus in NGC1068
We present results from a survey of nearby AGN using the near infrared
adaptive optics integral field spectrograph SINFONI. These data enable us to
probe the distribution and kinematics of the gas and stars at spatial
resolutions as small as 0.085arcsec. We find strong evidence for recent but
short lived starbursts residing in very dense nuclear disks. On scales of less
than 10pc these would have reached Eddington-limited luminosities when active,
perhaps accounting for their short duration. In addition, for NGC1068 at a
resolution of 6pc, we present direct observations of molecular gas close around
the AGN which we identify with the obscuring torus.Comment: Conference proceedings to appear in "The Central Engine of Active
Galactic Nuclei", ed. L. C. Ho and J.-M. Wang (San Francisco: ASP
Structural Invariance and the Energy Spectrum
We extend the application of the concept of structural invariance to bounded
time independent systems. This concept, previously introduced by two of us to
argue that the connection between random matrix theory and quantum systems with
a chaotic classical counterpart is in fact largely exact in the semiclassical
limit, is extended to the energy spectra of bounded time independent systems.
We proceed by showing that the results obtained previously for the
quasi-energies and eigenphases of the S-matrix can be extended to the
eigenphases of the quantum Poincare map which is unitary in the semiclassical
limit. We then show that its eigenphases in the chaotic case move rather
stiffly around the unit circle and thus their local statistical fluctuations
transfer to the energy spectrum via Bogomolny's prescription. We verify our
results by studying numerically the properties of the eigenphases of the
quantum Poincare map for billiards by using the boundary integral method.Comment: 10 pages, 5 figure
Rayleigh scattering and atomic dynamics in dissipative optical lattices
We investigate Rayleigh scattering in dissipative optical lattices. In particular, following recent proposals [S. Guibal et al., Phys. Rev. Lett. 78, 4709 (1997); C. Jurczak et al., Phys. Rev. Lett. 77, 1727 (1996)], we study whether the Rayleigh resonance originates from the diffraction on a density grating and is therefore a probe of transport of atoms in optical lattices. It turns out that this is not the case: the Rayleigh line is instead a measure of the cooling rate, while spatial diffusion contributes to the scattering spectrum with a much broader resonance
Breathers in FPU systems, near and far from the phonon band
There exists a recent mathematical proof on the existence of small amplitude
breathers in FPU systems near the phonon band, which includes a prediction of
their amplitude and width. In this work we obtain numerically these breathers,
and calculate the range of validity of the predictions, which extends
relatively far from the phonon band. There exist also large amplitude breathers
with the same frequency, with the consequence that there is an energy gap for
breather creation in these systems.Comment: 3 pages, 2 figures, proceeding of the conference on Localization and
to and Energy Transfer in Nonlinear Systems, June 17-21, 2002, San Lorenzo de
El Escorial, Madrid, Spain. To be published by World Scientifi
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