26,619 research outputs found
Effect of hybridization on the magnetic properties of correlated two-band metals
The magnetic properties of transition-like metals are discussed within the
single site approximation, which is a picture to take into account electron
correlations. The metal is described by two hybridized bands one of which
includes Coulomb correlation. The presented results indicate that
ferromagnetism arises for adequate values of hybridization (V), correlation (U)
and occupation number(). Some similarities with Dynamical
Mean-Field Theory (DMFT) are indicated.Comment: 3 pages, 3 figures, presented at the 53rd MMM08 conference in Austin,
200
Where is the fuzz? Undetected Lyman alpha nebulae around QSOs at z~2.3
We observed a small sample of 5 radio-quiet QSOs with integral field
spectroscopy to search for possible extended emission in the Ly line.
We subtracted the QSO point sources using a simple PSF self-calibration
technique that takes advantage of the simultaneous availability of spatial and
spectral information. In 4 of the 5 objects we find no significant traces of
extended Ly emission beyond the contribution of the QSO nuclei itself,
while in UM 247 there is evidence for a weak and spatially quite compact excess
in the Ly line at several kpc outside the nucleus. For all objects in
our sample we estimated detection limits for extended, smoothly distributed
Ly emission by adding fake nebulosities into the datacubes and trying
to recover them after PSF subtraction. Our observations are consistent with
other studies showing that giant Ly nebulae such as those found
recently around some quasars are very rare. Ly fuzz around typical
radio-quiet QSOs is fainter, less extended and is therefore much harder to
detect. The faintness of these structures is consistent with the idea that
radio-quiet QSOs typically reside in dark matter haloes of modest masses.Comment: 12 Pages, Accepted for publication in A&
Response of Bose gases in time-dependent optical superlattices
The dynamic response of ultracold Bose gases in one-dimensional optical
lattices and superlattices is investigated based on exact numerical time
evolutions in the framework of the Bose-Hubbard model. The system is excited by
a temporal amplitude modulation of the lattice potential, as it was done in
recent experiments. For regular lattice potentials, the dynamic signatures of
the superfluid to Mott-insulator transition are studied and the position and
the fine-structure of the resonances is explained by a linear response
analysis. Using direct simulations and the perturbative analysis it is shown
that in the presence of a two-colour superlattice the excitation spectrum
changes significantly when going from the homogeneous Mott-insulator the quasi
Bose-glass phase. A characteristic and experimentally accessible signature for
the quasi Bose-glass is the appearance of low-lying resonances and a
suppression of the dominant resonance of the Mott-insulator phase.Comment: 20 pages, 9 figures; added references and corrected typo
A new code for Fourier-Legendre analysis of large datasets: first results and a comparison with ring-diagram analysis
Fourier-Legendre decomposition (FLD) of solar Doppler imaging data is a
promising method to estimate the sub-surface solar meridional flow. FLD is
sensible to low-degree oscillation modes and thus has the potential to probe
the deep meridional flow. We present a newly developed code to be used for
large scale FLD analysis of helioseismic data as provided by the Global
Oscillation Network Group (GONG), the Michelson Doppler Imager (MDI)
instrument, and the upcoming Helioseismic and Magnetic Imager (HMI) instrument.
First results obtained with the new code are qualitatively comparable to those
obtained from ring-diagram analyis of the same time series.Comment: 4 pages, 2 figures, 4th HELAS International Conference "Seismological
Challenges for Stellar Structure", 1-5 February 2010, Arrecife, Lanzarote
(Canary Islands
Integral field spectroscopy of QSO host galaxies
We describe a project to study the state of the ISM in ~20 low redshift
(z<0.3) QSO host galaxies observed with the PMAS integral field spectrograph.
We describe method developement to access the stellar and gas component of the
spectrum without the strong nuclear emission to access the host galaxy
properties also in the central region. It shows that integral field
spectroscopy promises to be very efficient to study the gas distribution and
its velocity field, and also spatially resolved stellar population in the host
galaxies also of luminous AGN.Comment: 4 pages, 6 figures, Euro3D Science Workshop, Cambridge, May 2003, AN,
accepte
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