Viscous relaxation and collective oscillations in a trapped Fermi gas near the unitarity limit

The viscous relaxation time of a trapped two-component gas of fermions in its normal phase is calculated as a function of temperature and scattering length, with the collision probability being determined by an energy-dependent s-wave cross section. The result is used for calculating the temperature dependence of the frequency and damping of collective modes studied in recent experiments, starting from the kinetic equation for the fermion distribution function with mean-field effects included in the streaming terms.Comment: 10 pages, 9 figures; proof version, corrected typo in Eq. (23); accepted for publication in PR

Vanishing lines in generalized Adams spectral sequences are generic

We show that in a generalized Adams spectral sequence, the presence of a vanishing line of fixed slope (at some term of the spectral sequence, with some intercept) is a generic property.Comment: 11 pages. Published copy, also available at http://www.maths.warwick.ac.uk/gt/GTVol3/paper7.abs.htm

On the variance of sums of arithmetic functions over primes in short intervals and pair correlation for L-functions in the Selberg class

We establish the equivalence of conjectures concerning the pair correlation of zeros of $L$-functions in the Selberg class and the variances of sums of a related class of arithmetic functions over primes in short intervals. This extends the results of Goldston & Montgomery [7] and Montgomery & Soundararajan [11] for the Riemann zeta-function to other $L$-functions in the Selberg class. Our approach is based on the statistics of the zeros because the analogue of the Hardy-Littlewood conjecture for the auto-correlation of the arithmetic functions we consider is not available in general. One of our main findings is that the variances of sums of these arithmetic functions over primes in short intervals have a different form when the degree of the associated $L$-functions is 2 or higher to that which holds when the degree is 1 (e.g. the Riemann zeta-function). Specifically, when the degree is 2 or higher there are two regimes in which the variances take qualitatively different forms, whilst in the degree-1 case there is a single regime

Calculations of optimum seed concentrations in cesium and potassium non-equilibrium plasmas

Optimum seed concentrations in cesium and potassium non-equilibrium plasma

Viscosity and Thermal Relaxation for a resonantly interacting Fermi gas

The viscous and thermal relaxation rates of an interacting fermion gas are calculated as functions of temperature and scattering length, using a many-body scattering matrix which incorporates medium effects due to Fermi blocking of intermediate states. These effects are demonstrated to be large close to the transition temperature $T_c$ to the superfluid state. For a homogeneous gas in the unitarity limit, the relaxation rates are increased by nearly an order of magnitude compared to their value obtained in the absence of medium effects due to the Cooper instability at $T_c$. For trapped gases the corresponding ratio is found to be about three due to the averaging over the inhomogeneous density distribution. The effect of superfluidity below $T_c$ is considered to leading order in the ratio between the energy gap and the transition temperature.Comment: 7 pages, 3 figure

Active social location in schools: professional development for the whole school workforce?

The workforce in English schools has changed over recent years; there are more categories of staff to be found in English schools and the relative sizes of the categories have altered. Alongside these changes, the Every Child Matters reform programme implies the need to pay attention to the importance of all categories of staff to the welfare of children. However, there has not hitherto been an adequate characterisation of the nature of the practice of workers other than teachers . This paper attempts to characterise the position of school workers other than teachers to better understand the distinctive nature of their practice. We focus on Teaching Assistants, Caretakers and Lunchtime Supervisors as three groups which are sufficiently different to enable us to develop a richer theoretical account of identity in the school workforce than has hitherto been available. We have argued elsewhere (Coldron and Smith, 1999) that a teacher’s practice and his or her development of that practice can best be understood as a process of active social location. In this paper, we apply the same theoretical understanding of practice to the work identities of these three groups of school staff. By better understanding the identities that their different positions and associated resources make available, we aim to provide a richer picture and a way of thinking of the work identities of staff in school who are not teachers, one that is not colonised by the ways of thinking about the higher status teacher group.</p

ATMOS Spacelab 1 science investigation

Existing infrared spectra from high speed interferometer balloon flights were analyzed and experimental analysis techniques applicable to similar data from the ATMOS experiment (Spacelab 3) were investigated. Specific techniques under investigation included line-by-line simulation of the spectra to aid in the identification of absorbing gases, simultaneous retrieval of pressure and temperature profiles using carefully chosen pairs of CO2 absorption lines, and the use of these pressures and temperatures in the retrieval of gas concentration profiles for many absorbing species. A search for a new absorption features was also carried out, and special attention was given to identification of absorbing gases in spectral bandpass regions to be measured by the halogen occultation experiment

Measurement of the horizontal velocity of wind perturbations in the middle atmosphere by spaced MF radar systems

Two remote receiving sites have been set up at a distance of approx 40 km from the main MF radar system. This allows measurement of upper atmosphere winds from 60-120 km (3 km resolution) at the corners of an approximately equilateral triangle of side approx 20 km. Some preliminary data are compared through cross correlation and cross spectral analysis in an attempt to determine the horizontal velocity of wind perturbations and/or the horizontal wavelength and phase velocity of gravity waves