2,871 research outputs found
The confined-deconfined interface tension, wetting, and the spectrum of the transfer matrix
The reduced tension of the interface between the confined and
the deconfined phase of pure gauge theory is determined from numerical
simulations of the first transfer matrix eigenvalues. At we find
for . The interfaces show universal
behavior because the deconfined-deconfined interfaces are completely wet by the
confined phase. The critical exponents of complete wetting follow from the
analytic interface solutions of a -symmetric model in three
dimensions. We find numerical evidence that the confined-deconfined interface
is rough.Comment: Talk presented at the International Conference on Lattice Field
Theory, Lattice 92, to be published in the proceedings, 4 pages, 4 figures,
figures 2,3,4 appended as postscript files, figure 1 not available as a
postscript file but identical with figure 2 of Nucl. Phys. B372 (1992) 703,
special style file espcrc2.sty required (available from hep-lat), BUTP-92/4
A Multicanonical Algorithm and the Surface Free Energy in SU(3) Pure Gauge Theory
We present a multicanonical algorithm for the SU(3) pure gauge theory at the
deconfinement phase transition. We measure the tunneling times for lattices of
size L^3x2 for L=8,10, and 12. In contrast to the canonical algorithm the
tunneling time increases only moderately with L. Finally, we determine the
interfacial free energy applying the multicanonical algorithm.Comment: 6 pages, HLRZ-92-3
Relating Molecular Morphology to Charge Mobility in Semicrystalline Conjugated Polymers
The molecular-level origins of the effects of annealing temperature and molecular weight on hole mobility in P3HT are elucidated using coarse-grained molecular dynamics, quantum chemical calculations, and kinetic Monte Carlo charge-transport simulations on a variety of realistic thin-film morphologies. The zero-field hole mobility is shown to increase as the annealing temperature or average molecular weights of samples are increased, in accordance with experimental results. Crystal structure analysis shows that the annealing temperature dependence of the mobility can be attributed to the size and structural order of the crystallites in both the chain-backbone and π-stacking directions. However, the molecular weight dependence of the mobility cannot be rationalized in the same way. Longer chains are shown to belong to more crystallites in the morphology, suggesting that the crystals become better connected as the molecular weight of the sample increases. We show that engineering samples to have an increased fraction of these long “tie chains” within the morphology improves mobility. As such, we propose that crystal connectivity in the noncrystalline portions of the morphology is similarly important in determining carrier mobility as crystallite size and order for semicrystalline conjugated polymers
The Interface Tension in Quenched QCD at the Critical Temperature
We present results for the confinement-deconfinement interface tension
of quenched QCD. They were obtained by applying Binder's
histogram method to lattices of size for and
L=8,10,12\mbox{ and }14 with for and otherwise. The
use of a multicanonical algorithm and cylindrical geometries have turned out to
be crucial for the numerical studies.Comment: (talk presented by B. Grossmann at Lattice 92), 4 pages with 5 figure
appended as encapsulated postscript files at the end, preprint HLRZ-92-7
Charge fluctuations and electron-phonon interaction in the finite- Hubbard model
In this paper we employ a gaussian expansion within the finite-
slave-bosons formalism to investigate the momentum structure of the
electron-phonon vertex function in the Hubbard model as function of and
. The suppression of large momentum scattering and the onset a small- peak structure, parametrized by a cut-off , are shown to be
essentially ruled by the band narrowing factor due to the
electronic correlation. A phase diagram of and in the whole
- space is presented. Our results are in more than qualitative agreement
with a recent numerical analysis and permit to understand some anomalous
features of the Quantum Monte Carlo data.Comment: 4 pages, eps figures include
Diagnostic for Dilaton Dark Energy
diagnostic can differentiate between different models of dark energy
without the accurate current value of matter density. We apply this geometric
diagnostic to dilaton dark energy(DDE) model and differentiate DDE model from
LCDM. We also investigate the influence of coupled parameter on the
evolutive behavior of with respect to redshift . According to the
numerical result of , we get the current value of equation of state
=-0.952 which fits the WMAP5+BAO+SN very well.Comment: 6 pages and 6 figures
Proteorhodopsin overproduction enhances the long-term viability of Escherichia coli
Genes encoding the photoreactive protein proteorhodopsin (PR) have been found in a wide range of marine bacterial species, reflecting the significant contribution that PR makes to energy flux and carbon cycling in ocean ecosystems. PR can also confer advantages to enhance the ability of marine bacteria to survive periods of starvation. Here, we investigate the effect of heterologously produced PR on the viability of Escherichia coli. Quantitative mass spectrometry shows that E. coli, exogenously supplied with the retinal cofactor, assembles as many as 187,000 holo-PR molecules per cell, accounting for approximately 47% of the membrane area; even cells with no retinal synthesize ∼148,000 apo-PR molecules per cell. We show that populations of E. coli cells containing PR exhibit significantly extended viability over many weeks, and we use single-cell Raman spectroscopy (SCRS) to detect holo-PR in 9-month-old cells. SCRS shows that such cells, even incubated in the dark and therefore with inactive PR, maintain cellular levels of DNA and RNA and avoid deterioration of the cytoplasmic membrane, a likely basis for extended viability. The substantial proportion of the E. coli membrane required to accommodate high levels of PR likely fosters extensive intermolecular contacts, suggested to physically stabilize the cell membrane and impart a long-term benefit manifested as extended viability in the dark. We propose that marine bacteria could benefit similarly from a high PR content, with a stabilized cell membrane extending survival when those bacteria experience periods of severe nutrient or light limitation in the oceans
A low-voltage retarding-field Mott polarimeter for photocathode characterization
Nuclear physics experiments at Thomas Jefferson National Accelerator
Facility's CEBAF rely on high polarization electron beams. We describe a
recently commissioned system for prequalifying and studying photocathodes for
CEBAF with a load-locked, low-voltage polarized electron source coupled to a
compact retarding-field Mott polarimeter. The polarimeter uses simplified
electrode structures and operates from 5 to 30 kV. The effective Sherman
function for this device has been calibrated by comparison with the CEBAF 5 MeV
Mott polarimeter. For elastic scattering from a thick gold target at 20 keV,
the effective Sherman function is 0.201(5). Its maximum efficiency at 20 keV,
defined as the detected count rate divided by the incident particle current, is
5.4(2) x 10-4, yielding a figure-of-merit, or analyzing power squared times
efficiency, of 1.0(1) x 10-5. The operating parameters of this new polarimeter
design are compared to previously published data for other compact Mott
polarimeters of the retarding-field type.Comment: 9 figure
Time-dependent linear response of an inhomogeneous Bose superfluid: Microscopic theory and connection to current-density functional theory
The dynamics of a confined fluid of Bose atoms is treated within the linear
response regime, with a view to establishing a current-density functional
formalism for an inhomogeneous superfluid state. After evaluating in full
detail a simplified case of an external coupling to the density and phase of
the condensate, the theory is extended to include the coupling to the total
current density. The Kohn-Sham response functions of the condensate and all the
exchange-correlation kernels for the superfluid are introduced from the
microscopic equations of motion and are expressed in a physically transparent
way through functional derivatives of correlation functions. A microscopic
formula for the superfluid density is derived and used to introduce a
generalized hydrodynamic approach for a weakly inhomogeneous two-fluid model in
isothermal conditions. Local-density expressions are thereby derived for the
velocities of first and second sound in the weakly inhomogeneous superfluid and
for visco-elastic functions describing the transition from the hydrodynamic to
the collisionless regime. Landau's hydrodynamic theory and known results in
Green's functions language are recovered in the limiting case of a homogeneous
superfluid.Comment: 25 pages, no figures, Postscript fil
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