2,340 research outputs found
Percolation model for nodal domains of chaotic wave functions
Nodal domains are regions where a function has definite sign. In recent paper
[nlin.CD/0109029] it is conjectured that the distribution of nodal domains for
quantum eigenfunctions of chaotic systems is universal. We propose a
percolation-like model for description of these nodal domains which permits to
calculate all interesting quantities analytically, agrees well with numerical
simulations, and due to the relation to percolation theory opens the way of
deeper understanding of the structure of chaotic wave functions.Comment: 4 pages, 6 figures, Late
Spectral Variability of Quasars in the Sloan Digital Sky Survey. II: The C IV Line
We examine the variability of the high-ionizaton C IV line in a sample of 105
quasars observed at multiple epochs by the Sloan Digital Sky Survey. We find a
strong correlation between the change in the C IV line flux and the change in
the line width, but no correlations between the change in flux and changes in
line center and skewness. The relation between line flux change and line width
change is consistent with a model in which a broad line base varies with
greater amplitude than the line core. The objects studied here are more
luminous and at higher redshift than those normally studied for variability,
ranging in redshift from 1.65 to 4.00 and in absolute r-band magnitude from
roughly -24 to -28. Using moment analysis line-fitting techniques, we measure
line fluxes, centers, widths and skewnesses for the C IV line at two epochs for
each object. The well-known Baldwin Effect is seen for these objects, with a
slope beta = -0.22. The sample has a median intrinsic Baldwin Effect slope of
beta = -0.85; the C IV lines in these high-luminosity quasars appear to be less
responsive to continuum variations than those in lower luminosity AGN.
Additionally, we find no evidence for variability of the well known blueshift
of the C IV line with respect to the low-ionization Mg II line in the highest
flux objects, indicating that this blueshift might be useful as a measure of
orientation.Comment: 52 pages, 14 figures, accepted for publication in Ap
The Black Hole-Bulge Relationship in Luminous Broad-Line Active Galactic Nuclei and Host Galaxies
We have measured the stellar velocity dispersions (\sigma_*) and estimated
the central black hole (BH) masses for over 900 broad-line active galactic
nuclei (AGNs) observed with the Sloan Digital Sky Survey. The sample includes
objects which have redshifts up to z=0.452, high quality spectra, and host
galaxy spectra dominated by an early-type (bulge) component. The AGN and host
galaxy spectral components were decomposed using an eigenspectrum technique.
The BH masses (M_BH) were estimated from the AGN broad-line widths, and the
velocity dispersions were measured from the stellar absorption spectra of the
host galaxies. The range of black hole masses covered by the sample is
approximately 10^6 < M_BH < 10^9 M_Sun. The host galaxy luminosity-velocity
dispersion relationship follows the well-known Faber-Jackson relation for
early-type galaxies, with a power-law slope 4.33+-0.21. The estimated BH masses
are correlated with both the host luminosities (L_{H}) and the stellar velocity
dispersions (\sigma_*), similar to the relationships found for low-redshift,
bulge-dominated galaxies. The intrinsic scatter in the correlations are large
(~0.4 dex), but the very large sample size allows tight constraints to be
placed on the mean relationships: M_BH ~ L_H^{0.73+-0.05} and M_BH ~
\sigma_*^{3.34+-0.24}. The amplitude of the M_BH-\sigma_* relation depends on
the estimated Eddington ratio, such that objects with larger Eddington ratios
have smaller black hole masses than expected at a given velocity dispersion.Comment: Accepted for publication in A
Trapped Li : A high T_c superfluid ?
We consider the effect of the indirect interaction due to the exchange of
density fluctuations on the critical temperature of superfluid Li . We
obtain the strong coupling equation giving this critical temperature. This
equation is solved approximately by retaining the same set of diagrams as in
the paramagnon model. We show that, near the instability threshold, the
attractive interaction due to density fluctuations gives rise to a strong
increase in the critical temperature, providing a clear signature of the
existence of fluctuation induced interactions.Comment: 4 pages, revtex, 1 figur
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Indoor air quality measurements in energy efficient buildings
The Energy Efficient Buildings Program of the Lawrence Berkeley Laboratory (LBL) has designed and fabricated a mobile laboratory for research and development studies of ventilation requirements and energy utilization in residential and commercial buildings. The Energy Efficient Buildings (EEB) Mobile Laboratory is used in studies of indoor air quality in buildings before and after energy conservation retrofits and in new buildings incorporating energy efficient designs. Indoor air quality measurements have been conducted in residential buildings and work in progress includes indoor air quality monitoring in schools, hospitals, and energy efficient residential buildings. The monitoring program includes measurement of CO, CO/sub 2/, SO/sub 2/, NO, NO/sub 2/, O/sub 3/, infiltration rate (tracer gas technique), and aerosol size distribution on a continuous basis. Total and respirable-fraction particulate samples are collected on membrane filter media for analysis by x-ray fluorescence (XRFA), photoelectron spectroscopy (ESCA), proton activation analysis (PAA), combustion, and wet-chemistry techniques for the determination of particulate elemental composition (S, N, C, etc.) and ionic species such as SO/sub 4//sup 2 -/, NO/sub 3//sup -/, and NH/sub 4//sup +/. Results of the initial phases of this program indicate that the concentrations of some gaseous and respirable particulate air pollutants in specific indoor environments exceed those levels commonly found in the outdoor urban air environment
Discovery of the Most-Distant Double-Peaked Emitter at z=1.369
We report the discovery of the most-distant double-peaked emitter, CXOECDFS
J033115.0-275518, at z=1.369. A Keck/DEIMOS spectrum shows a clearly
double-peaked broad Mg II emission line, with FWHM 11000 km/s for
the line complex. The line profile can be well fit by an elliptical
relativistic Keplerian disk model. This is one of a handful of double-peaked
emitters known to be a luminous quasar, with excellent multiwavelength coverage
and a high-quality X-ray spectrum. CXOECDFS J033115.0-275518 is a radio-loud
quasar with two radio lobes (FR II morphology) and a radio loudness of f_{5
GHz}/f_{4400 \AA}~429. The X-ray spectrum can be modeled by a power law with
photon index 1.72 and no intrinsic absorption; the rest-frame 0.5-8.0 keV
luminosity is erg/s. The spectral energy distribution (SED)
of CXOECDFS J033115.0-275518 has a shape typical for radio-loud quasars and
double-peaked emitters at lower redshift. The local viscous energy released
from the line-emitting region of the accretion disk is probably insufficient to
power the observed line flux, and external illumination of the disk appears to
be required. The presence of a big blue bump in the SED along with the
unexceptional X-ray spectrum suggest that the illumination cannot arise from a
radiatively inefficient accretion flow.Comment: 6 pages, 5 figures, ApJ in pres
The Optical, Infrared and Radio Properties of Extragalactic Sources Observed by SDSS, 2MASS and FIRST Surveys
We positionally match sources observed by the Sloan Digital Sky Survey
(SDSS), the Two Micron All Sky Survey (2MASS), and the Faint Images of the
Radio Sky at Twenty-cm (FIRST) survey. Practically all 2MASS sources are
matched to an SDSS source within 2 arcsec; ~11% of them are optically resolved
galaxies and the rest are dominated by stars. About 1/3 of FIRST sources are
matched to an SDSS source within 2 arcsec; ~80% of these are galaxies and the
rest are dominated by quasars. Based on these results, we project that by the
completion of these surveys the matched samples will include about 10^7 stars
and 10^6 galaxies observed by both SDSS and 2MASS, and about 250,000 galaxies
and 50,000 quasars observed by both SDSS and FIRST. Here we present a
preliminary analysis of the optical, infrared and radio properties for the
extragalactic sources from the matched samples. In particular, we find that the
fraction of quasars with stellar colors missed by the SDSS spectroscopic survey
is probably not larger than ~10%, and that the optical colors of radio-loud
quasars are ~0.05 mag. redder (with 4-sigma significance) than the colors of
radio-quiet quasars.Comment: 10 pages, 6 color figures, presented at IAU Colloquium 184. AGN
Survey
Renormalization of the elementary excitations in hole- and electron-doped cuprates due to spin fluctuations
Extending our previous studies we present results for the doping-, momentum-,
frequency-, and temperature- dependence of the kink-like change of the
quasiparticle velocity resulting from the coupling to spin fluctuations. In the
nodal direction a kink is found in both the normal and superconducting state
while in the antinodal direction a kink occurs only below due to the
opening of the superconducting gap. A pronounced kink is obtained only for
hole-doped, but not for electron-doped cuprates and is characteristically
different from what is expected due to electron-phonon interaction. We further
demonstrate that the kink structure is intimately connected to the resonance
peak seen in inelastic neutron scattering. Our results suggest similar effects
in other unconventional superconductors like .Comment: revised version, 12 pages, 19 figures. accepted for publication in
PR
Swift XRT and UVOT deep observations of the high energy peaked BL Lac object PKS 0548-322 close to its brightest state
We present the results of a spectral analysis of 5 Swift XRT and UVOT
observations of the BL Lac object PKS 0548-322 carried out over the period
April-June 2005. The X-ray flux of this high energy peaked BL Lac (HBL) source
was found to be approximately constant at a level of F(2-10 keV) ~ 4x10^-11 erg
cm^-2 s^-1, a factor of 2 brighter than when observed by BeppoSAX in 1999 and
close to the maximum intensity reported in the Einstein Slew Survey. The very
good statistics obtained in the 0.3-10 keV Swift X-ray spectrum allowed us to
detect highly significant deviations from a simple power law spectral
distribution. A log-parabolic model describes well the X-ray data and gives a
best fit curvature parameter of 0.18 and peak energy in the Spectral Energy
Distribution of about 2 keV. The UV spectral data from Swift UVOT join well
with a power law extrapolation of the soft X-ray data points suggesting that
the same component is responsible for the observed emission in the two bands.
The combination of synchrotron peak in the X-ray band and high intensity state
confirms PKS 0548-322 as a prime target for TeV observations. X-ray monitoring
and coordinated TeV campaigns are highly advisable.Comment: Accepted for publication in A&A (6 pages, 3 figures
Stability of annular equilibrium of energetic large orbit ion beam
The low-frequency stability of a long thin annular layer of energetic ions in a background plasma with finite axial and zero azimuthal magnetic field is studied analytically. It is found that although the equilibrium is susceptible to the kink instability, low mode number perturbations can be stabilized in the limit of N(i)/N(b) --> O when the current layer is close to the maximum field-reversal parameter. A brief discussion of the tearing mode stability criteria of such strong current layers with respect to the placement of conducting walls is also presented
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