38,047 research outputs found
Magnetic field effects on the finite-frequency noise and ac conductance of a Kondo quantum dot out of equilibrium
We present analytic results for the finite-frequency current noise and the
nonequilibrium ac conductance for a Kondo quantum dot in presence of a magnetic
field. Using the real-time renormalization group method, we determine the line
shape close to resonances and show that while all resonances in the ac
conductance are broadened by the transverse spin relaxation rate, the noise at
finite field additionally involves the longitudinal rate as well as sharp kinks
resulting in singular derivatives. Our results provide a consistent theoretical
description of recent experimental data for the emission noise at zero magnetic
field, and we propose the extension to finite field for which we present a
detailed prediction.Comment: 21 pages, 13 figure
Score-Informed Source Separation for Musical Audio Recordings [An overview]
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A Modified "Bottom-up" Thermalization in Heavy Ion Collisions
In the initial stage of the bottom-up picture of thermalization in heavy ion
collisions, the gluon distribution is highly anisotropic which can give rise to
plasma instability. This has not been taken account in the original paper. It
is shown that in the presence of instability there are scaling solutions, which
depend on one parameter, that match smoothly onto the late stage of bottom-up
when thermalization takes place.Comment: 8 pages and 1 embedded figure, talk presented at the Workshop on
"Quark-Gluon Plasma Thermalization", Vienna, Austria, 10-12 August 200
Domain wall dynamics in a two-component Bose-Mott insulator
We model the dynamics of two species of bosonic atoms trapped in an optical
lattice within the Mott regime by mapping the system onto a spin model. A field
gradient breaks the cloud into two domains. We study how the domain wall
evolves under adiabatic and diabatic changes of this gradient. We determine the
timescales for adiabaticity, and study how temperature evolves for slow ramps.
We show that after large, sudden changes of the field gradient, the system does
not equilibrate on typical experimental timescales. We find interesting spin
dynamics even when the initial temperature is large compared to the
super-exchange energy. We discuss the implication of our results for
experiments wishing to use such a two-component system for thermometry, or as
part of a cooling scheme.Comment: 6 pages, 5 figures Minor typographical errors corrected. Figure
labels changed. Added concluding statement
The colour-magnitude relation of Globular Clusters in Centaurus and Hydra - Constraints on star cluster self-enrichment with a link to massive Milky Way GCs
We investigate the colour-magnitude relation of metal-poor globular clusters,
the 'blue tilt', in the Hydra and Centaurus galaxy clusters and constrain the
primordial conditions for star cluster self-enrichment. We analyse U,I
photometry for about 2500 globular clusters in the central regions of Hydra and
Centaurus, based on FORS1@VLT data. We convert the measured colour-magnitude
relations into mass-metallicity space and obtain a scaling of Z \propto M^{0.27
\pm 0.05} for Centaurus GCs and Z \propto M^{0.40 \pm 0.06} for Hydra GCs,
consistent with results in other environments. We find that the GC
mass-metallicity relation already sets in at present-day masses of a few 10^5
solar masses and is well established in the luminosity range of massive MW
clusters like omega Centauri. We compare the mass-metallicity relation with
predictions from the star cluster self-enrichment model by Bailin & Harris
(2009). For this we include effects of dynamical and stellar evolution and a
physically well motivated primordial mass-radius scaling. The self-enrichment
model reproduces the observed relations well for average primordial half-light
radii r_h ~ 1-1.5 pc, star formation efficiencies f_* ~ 0.3-0.4, and
pre-enrichment levels of [Fe/H] ~ -1.7 dex. Within the self-enrichment
scenario, the observed blue tilt implies a correlation between GC mass and
width of the stellar metallicity distribution. We find that this implied
correlation matches the trend of width with GC mass measured in Galactic GCs,
including extreme cases like omega Cen and M54. We conclude that 1. A
primordial star cluster mass-radius relation provides a significant improvement
to the self-enrichment model fits. 2. Broadenend metallicity distributions as
found in some massive MW globular clusters may have arisen naturally from
self-enrichment processes, without the need of a dwarf galaxy progenitor.Comment: 15 pages, 13 figures. Language edited version of paper accepted for
publication in Astronomy & Astrophysics. Colour-composite in Figure 1 reduced
in resolutio
Differential regulation of Ota and Otb, two primary glycine betaine transporters in the methanogenic archaeon Methanosarcina mazei go1
Methanogenic archaea accumulate glycine betaine in response to hypersalinity, but the regulation of proteins involved, their mechanism of activation and regulation of the corresponding genes are largely unknown. Methanosarcina mazei differs from most other methanoarchaea in having two gene clusters both encoding a potential glycine betaine transporter, Ota and Otb. Western blot as well as quantitative real-time PCR revealed that Otb is not regulated by osmolarity. On the other hand, cellular levels of Ota increased with increasing salt concentrations. A maximum was reached at 300-500 m M NaCl. Ota concentrations reached a maximum 4 h after an osmotic upshock. Hyperosmolarity also caused an increase in cellular Ota concentrations. In addition to osmolarity Ota expression was regulated by the growth phase. Expression of Ota as well as transport of betaine was downregulated in the presence of glycine betaine. Copyright (c) 2007 S. Karger AG, Basel
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