11,960 research outputs found
Electrical conductivity and thermal dilepton rate from quenched lattice QCD
We report on a continuum extrapolation of the vector current correlation
function for light valence quarks in the deconfined phase of quenched QCD. This
is achieved by performing a systematic analysis of the influence of cut-off
effects on light quark meson correlators at using clover
improved Wilson fermions. We discuss resulting constraints on the electrical
conductivity and the thermal dilepton rate in a quark gluon plasma. In addition
new results at 1.2 and 3.0 will be presented.Comment: 4 pages, 6 eps figures, to appear in the proceedings of Quark Matter
2011, 23-28 May 2011, Annecy, Franc
Uranium(III) coordination chemistry and oxidation in a flexible small-cavity macrocycle
U(III) complexes of the conformationally flexible, small-cavity macrocycle trans-calix[2]benzene[2]pyrrolide (L)2–, [U(L)X] (X = O-2,6-tBu2C6H3, N(SiMe3)2), have been synthesized from [U(L)BH4] and structurally characterized. These complexes show binding of the U(III) center in the bis(arene) pocket of the macrocycle, which flexes to accommodate the increase in the steric bulk of X, resulting in long U–X bonds to the ancillary ligands. Oxidation to the cationic U(IV) complex [U(L)X][B(C6F5)4] (X = BH4) results in ligand rearrangement to bind the smaller, harder cation in the bis(pyrrolide) pocket, in a conformation that has not been previously observed for (L)2–, with X located between the two ligand arene rings
Effective dynamics of an electrically charged string with a current
Equations of motion for an electrically charged string with a current in an
external electromagnetic field with regard to the first correction due to the
self-action are derived. It is shown that the reparametrization invariance of
the free action of the string imposes constraints on the possible form of the
current. The effective equations of motion are obtained for an absolutely
elastic charged string in the form of a ring (circle). Equations for the
external electromagnetic fields that admit stationary states of such a ring are
revealed. Solutions to the effective equations of motion of an absolutely
elastic charged ring in the absence of external fields as well as in an
external uniform magnetic field are obtained. In the latter case, the frequency
at which one can observe radiation emitted by the ring is evaluated. A model of
an absolutely nonstretchable charged string with a current is proposed. The
effective equations of motion are derived within this model, and a class of
solutions to these equations is found.Comment: 14 pages, 3 figures, format changed, minor change
The phase-dependent linear conductance of a superconducting quantum point contact
The exact expression for the phase-dependent linear conductance of a weakly
damped superconducting quantum point contact is obtained. The calculation is
performed by summing up the complete perturbative series in the coupling
between the electrodes. The failure of any finite order perturbative expansion
in the limit of small voltage and small quasi-particle damping is analyzed in
detail. In the low transmission regime this nonperturbative calculation yields
a result which is at variance with standard tunnel theory. Our result predicts
the correct sign of the quasi-particle pair interference term and exhibits an
unusual phase-dependence at low temperatures in qualitative agreement with the
available experimental data.Comment: 12 pages (revtex) + 1 postscript figure. Submitted to Phys. Rev. Let
Output Management for Agriculture?
Could agriculture learn to manage its output from some other industries? Some industries have experience in managing excess capacity. Agriculture might want to look at the alternative methods and their consequences
A Time-Orbiting Potential Trap for Bose-Einstein Condensate Interferometry
We describe a novel atom trap for Bose-Einstein condensates of 87Rb to be
used in atom interferometry experiments. The trap is based on a time-orbiting
potential waveguide. It supports the atoms against gravity while providing weak
confinement to minimize interaction effects. We observe harmonic oscillation
frequencies omega_x, omega_y, omega_z as low as 2 pi times (6.0,1.2,3.3) Hz. Up
to 2 times 10^4 condensate atoms have been loaded into the trap, at estimated
temperatures as low as 850 pK. We anticipate that interferometer measurement
times of 1 s or more should be achievable in this device.Comment: 9 pages, 3 figure
Weed Control in Small Grain
This publication provides guidance on general control methods, herbicide facts and recommendations, cropping, and noxious weed control for spring and winter grains. It includes diagrams and tables for assistance in determining small grain growth stages, herbicide cost and quantity, and susceptibility of small grain varieties to certain chemical applications
Could Nano-Structured Materials Enable the Improved Pressure Vessels for Deep Atmospheric Probes?
A viewgraph presentation on the use of Nano-Structured Materials to enable pressure vessel structures for deep atmospheric probes is shown. The topics include: 1) High Temperature/Pressure in Key X-Environments; 2) The Case for Use of Nano-Structured Materials Pressure Vessel Design; 3) Carbon based Nanomaterials; 4) Nanotube production & purification; 5) Nanomechanics of Carbon Nanotubes; 6) CNT-composites: Example (Polymer); 7) Effect of Loading sequence on Composite with 8% by volume; 8) Models for Particulate Reinforced Composites; 9) Fullerene/Ti Composite for High Strength-Insulating Layer; 10) Fullerene/Epoxy Composite for High Strength-Insulating Layer; 11) Models for Continuous Fiber Reinforced Composites; 12) Tensile Strength for Discontinuous Fiber Composite; 13) Ti + SWNT Composites: Thermal/Mechanical; 14) Ti + SWNT Composites: Tensile Strength; and 15) Nano-structured Shell for Pressure Vessels
Screened Perturbation Theory to Three Loops
The thermal physics of a massless scalar field with a phi^4 interaction is
studied within screened perturbation theory (SPT). In this method the
perturbative expansion is reorganized by adding and subtracting a mass term in
the lagrangian. We consider several different mass prescriptions that
generalize the one-loop gap equation to two-loop order. We calculate the
pressure and entropy to three-loop order and the screening mass to two-loop
order. In contrast to the weak-coupling expansion, the SPT-improved
approximations appear to converge even for rather large values of the coupling
constant.Comment: 30 pages, 10 figure
The turbulent spectrum created by non-Abelian plasma instabilities
Recent numerical work on the fate of plasma instabilities in weakly-coupled
non-Abelian gauge theory has shown the development of a cascade of energy from
long to short wavelengths. This cascade has a steady-state spectrum, analogous
to the Kolmogorov spectrum for turbulence in hydrodynamics or for energy
cascades in other systems. In this paper, we theoretically analyze processes
responsible for this cascade and find a steady-state spectrum f_k ~ k^-2, where
f_k is the phase-space density of particles with momentum k. The exponent -2 is
consistent with results from numerical simulations. We also discuss
implications of the emerging picture of instability development on the
"bottom-up" thermalization scenario for (extremely high energy) heavy ion
collisions, emphasizing fundamental questions that remain to be answered.Comment: 17 pages, 5 figure
- …