Genuine phase diffusion of a Bose-Einstein condensate in the microcanonical ensemble: A classical field study

Within the classical field model, we find that the phase of a Bose-Einstein condensate undergoes a true diffusive motion in the microcanonical ensemble, the variance of the condensate phase change between time zero and time $t$ growing linearly in $t$. The phase diffusion coefficient obeys a simple scaling law in the double thermodynamic and Bogoliubov limit. We construct an approximate calculation of the diffusion coefficient, in fair agreement with the numerical results over the considered temperature range, and we extend this approximate calculation to the quantum field.Comment: 9 pages, 6 figure

Epeoloides pilosulus (Cresson) Rediscovered in Michigan, with Notes on the Distribution and Status of its Macropis hosts.

Epeoloides pilosulus (Cresson 1878) is one of the rarest bees in North America with only a handful of records since 1960. The last collection in Michigan was made in 1944. Epeoloides pilosulus is a brood parasite of Macropis bees, which until recently had not been collected in Michigan for several decades. Bee surveys in Midland County, Michigan have led to the rediscovery of E. pilosulus in this state – the first record in 74 years. Michigan becomes the fourth state where E. pilosulus has been rediscovered after Connecticut in 2006, New York in 2014 and Maine in 2016, and the sixth region in North America after Nova Scotia in 2002 and Alberta in 2010. State-wide bee surveys have also shown that the principal host, Macropis nuda (Provancher 1882), remains widespread in Michigan, and that Macropis patellata Patton 1880 is newly recorded for the state

Canonical quantization of the WZW model with defects and Chern-Simons theory

We perform canonical quantization of the WZW model with defects and permutation branes. We establish symplectomorphism between phase space of WZW model with $N$ defects on cylinder and phase space of Chern-Simons theory on annulus times $R$ with $N$ Wilson lines, and between phase space of WZW model with $N$ defects on strip and Chern-Simons theory on disc times $R$ with $N+2$ Wilson lines. We obtained also symplectomorphism between phase space of the $N$-fold product of the WZW model with boundary conditions specified by permutation branes, and phase space of Chern-Simons theory on sphere with $N$ holes and two Wilson lines.Comment: 26 pages, minor corrections don

Effects of accidental microconstriction on the quantized conductance in long wires

We have investigated the conductance of long quantum wires formed in GaAs/AlGaAs heterostructures. Using realistic fluctuation potentials from donor layers we have simulated numerically the conductance of four different kinds of wires. While ideal wires show perfect quantization, potential fluctuations from random donors may give rise to strong conductance oscillations and degradation of the quantization plateaux. Statistically there is always the possibility of having large fluctuations in a sample that may effectively act as a microconstriction. We therefore introduce microconstrictions in the wires by occasional clustering of donors. These microconstrictions are found to restore the quantized plateaux. A similar effect is found for accidental lithographic inaccuracies.Comment: 4 pages, 2 figures, paper for NANO2002 symposium, will appear in SPIE proceeding

The contrasting oceanography of the Rhodes Gyre and the Central Black Sea

The Rhodes Gyre, a prominent feature of the oceanography of the eastern Mediterranean, is modelled as a vertical, continuous flow, cylindrical reactor illuminated during the day at its upper end. If the Gyre is supposed to be in a steady state whilst the concentrations, C, of a chemical are being measured, the nett rate of formation or consumption of the chemical is given by -w d C/d z + u d C/d r, where w is the upward velocity of the water in the vertical, z , direction and u is the velocity of the water in the radial, r, direction. The behaviour of w and u is analysed to show that the Gyre may be used as a field laboratory in which rates of chemical change may be derived from depth profiles together with values of the surface velocities of the Gyre waters. In contrast, the central Black Sea is modelled as an ideal, strongly stratified sea in which the nett rates of formation or consumption of chemicals under steady state conditions are given by Ds d2C/ds 2, where s is the water density and Ds is an eddy diffusion coefficient. Computations reveal that, given better knowledge of its eddy diffusion coefficients, the Black Sea can also be treated as a field laboratory where rates of reaction mediated by bacteria may be derived from depth profiles