8 research outputs found
Vortices in superfluid trapped Fermi gases at zero temperature
We discuss various aspects of the vortex state of a dilute superfluid atomic
Fermi gas at T=0. The energy of the vortex in a trapped gas is calculated and
we provide an expression for the thermodynamic critical rotation frequency of
the trap for its formation. Furthermore, we propose a method to detect the
presence of a vortex by calculating the effect of its associated velocity field
on the collective mode spectrum of the gas
Retrodictively Optimal Localisations in Phase Space
In a previous paper it was shown that the distribution of measured values for
a retrodictively optimal simultaneous measurement of position and momentum is
always given by the initial state Husimi function. This result is now
generalised to retrodictively optimal simultaneous measurements of an arbitrary
pair of rotated quadratures x_theta1 and x_theta2. It is shown, that given any
such measurement, it is possible to find another such measurement,
informationally equivalent to the first, for which the axes defined by the two
quadratures are perpendicular. It is further shown that the distribution of
measured values for such a meaurement belongs to the class of generalised
Husimi functions most recently discussed by Wuensche and Buzek. The class
consists of the subset of Wodkiewicz's operational probability distributions
for which the filter reference state is a squeezed vaccuum state.Comment: 11 pages, 2 figures. AMS Latex. Replaced with published versio
Signatures of resonance superfluidity in a quantum Fermi gas
In this letter, we predict a direct and observable signature of the
superfluid phase in a quantum Fermi gas, in a temperature regime already
accessible in current experiments. We apply the theory of resonance
superfluidity to a gas confined in a harmonic potential and demonstrate that a
significant increase in density will be observed in the vicinity of the trap
center.Comment: 4 pages, 4 figure
Impurity breakdown and terahertz luminescence in n-GaN epilayers under external electric field
We report on the observation and experimental studies of impurity breakdown and terahertz luminescence in n-GaN epilayers under external electric field. The terahertz electroluminescence is observed in a wide range of doping levels (at noncompensated donor density from 4.5×10[sup 16] to 3.4×10[sup 18] cm[sup −3]). Spectra of terahertz luminescence and photoconductivity are studied by means of Fourier transform spectrometry. Distinctive features of the spectra can be assigned to intracenter electron transitions between excited and ground states of silicon and oxygen donors and to hot electron transitions to the donor states.Peer reviewe
High street changeability: the effect of urban form on demolition, modification and use change in two south London suburbs
Adaptability and resilience are recognized as essential elements of urban sustainability, yet
they remain elusive as propositions supported by empirical research. In the research presented here the
affordance of change and continuity – here termed changeability – is investigated through a comparative
historical study of two suburban centres in London ‒ Surbiton and South Norwood ‒ which have matured
differently, despite many extrinsic similarities. Their development c.1880-2013 is examined through the
analysis of digitized historical maps, building use and space syntax analysis of their street plans.
Buildings on busy, but not necessarily the busiest, streets in small town centres are said to be the most
changeable since they can accommodate a variety of non-domestic uses. The plot dimensions on such
streets tend to facilitate incremental building modifications and cyclical redevelopment