A Generalization of Haldane state-counting procedure and π\pi-deformations of statistics

We consider the generalization of Haldane's state-counting procedure to describe all possible types of exclusion statistics which are linear in the deformation parameter $g$. The statistics are parametrized by elements of the symmetric group of the particles in question. For several specific cases we determine the form of the distribution functions which generalizes results obtained by Wu. Using them we analyze the low-temperature behavior and thermodynamic properties of these systems and compare our results with previous studies of the thermodynamics of a gas of $g$-ons. Various possible physical applications of these constructions are discussed.Comment: 17 pages, latex, 6 figures small corrections were made, reference and acknowledgments are adde

Wavefront shaping of a Bessel light field enhances light sheet microscopy with scattered light

The project was supported by the UK Engineering and Physical Sciences Research Council, RS MacDonald Charitable Trust, SULSA, and the St. Andrews 600th anniversary BRAINS appeal. K. D. is a Royal Society Wolfson Merit Award holder.Light sheet microscopy has seen a resurgence as it facilitates rapid, high contrast, volumetric imaging with minimal sample exposure. Initially developed for imaging scattered light, this application of light sheet microscopy has largely been overlooked but provides an endogenous contrast mechanism which can complement fluorescence imaging and requires very little or no modification to an existing light sheet fluorescence microscope. Fluorescence imaging and scattered light imaging differ in terms of image formation. In the former the detected light is incoherent and weak whereas in the latter the coherence properties of the illumination source, typically a laser, dictate the coherence of detected light, but both are dependent on the quality of the illuminating light sheet. Image formation in both schemes can be understood as the convolution of the light sheet with the specimen distribution. In this paper we explore wavefront shaping for the enhancement of light sheet microscopy with scattered light. We show experimental verification of this result, demonstrating the use of the propagation invariant Bessel beam to extend the field of view of a high resolution scattered light, light sheet microscope and its application to imaging of biological super-cellular structures with sub-cellular resolution. Additionally, complementary scattering and fluorescence imaging is used to characterize the enhancement, and to develop a deeper understanding of the differences of image formation between contrast mechanisms in light sheet microscopy.Publisher PD

Exact vortex nucleation and cooperative vortex tunneling in dilute BECs

With the imminent advent of mesoscopic rotating BECs in the lowest Landau level (LLL) regime, we explore LLL vortex nucleation. An exact many-body analysis is presented in a weakly elliptical trap for up to 400 particles. Striking non-mean field features are exposed at filling factors >>1 . Eg near the critical rotation frequency pairs of energy levels approach each other with exponential accuracy. A physical interpretation is provided by requantising a mean field theory, where 1/N plays the role of Planck's constant, revealing two vortices cooperatively tunneling between classically degenerate energy minima. The tunnel splitting variation is described in terms of frequency, particle number and ellipticity.Comment: 4 pages,4 figure

Anomalous hydrodynamics and "normal" fluids in rapidly rotating BECs

In rapidly rotating bose systems we show that there is a region of anomalous hydrodynamics whilst the system is still condensed, which coincides with the mean field quantum Hall regime. An immediate consequence is the absence of a normal fluid in any conventional sense. However, even the superfluid hydrodynamics is not described by conventional Bernoulli and continuity equations. We show there are kinematic constraints which connect spatial variations of density and phase, that the positions of vortices are not the simplest description of the dynamics of such a fluid (despite their utility in describing the instantaneous state of the condensate) and that the most compact description allows solution of some illuminating examples of motion. We demonstrate, inter alia, a very simple relation between vortices and surface waves. We show the surface waves can form a "normal fluid" which absorbs energy and angular momentum from vortex motion in the trap. The time scale of this process is sensitive to the initial configuration of the vortices, which can lead to long-lived vortex patches - perhaps related to those observed at JILA.Comment: 4 pages; 1 sentence and references modifie

Condensation of `composite bosons' in a rotating BEC

We provide evidence for several novel phases in the dilute limit of rotating BECs. By exact calculation of wavefunctions and energies for small numbers of particles, we show that the states near integer angular momentum per particle are best considered condensates of composite entities, involving vortices and atoms. We are led to this result by explicit comparison with a description purely in terms of vortices. Several parallels with the fractional quantum Hall effect emerge, including the presence of the Pfaffian state.Comment: 4 pages, Latex, 3 figure

Investigating Ca II emission in the RS CVn binary ER Vulpeculae using the Broadening Function Formalism

The synchronously rotating G stars in the detached, short-period (0.7 d), partially eclipsing binary, ER Vul, are the most chromospherically active solar-type stars known. We have monitored activity in the Ca II H & K reversals for almost an entire orbit. Rucinski's Broadening Function Formalism allows the photospheric contribution to be objectively subtracted from the highly blended spectra. The power of the BF technique is also demonstrated by the good agreement of radial velocities with those measured by others from less crowded spectral regions. In addition to strong Ca II emission from the primary and secondary, there appears to be a high-velocity stream flowing onto the secondary where it stimulates a large active region on the surface 30 - 40 degrees in advance of the sub-binary longitude. A model light curve with a spot centered on the same longitude also gives the best fit to the observed light curve. A flare with approximately 13% more power than at other phases was detected in one spectrum. We suggest ER Vul may offer a magnified view of the more subtle chromospheric effects synchronized to planetary revolution seen in certain `51 Peg'-type systems.Comment: Accepted to AJ; 17 pages and 16 figure

Bosons in a random potential: condensation and screening in a dense limit

Abstract. We demonstrate that an extended Bose condensate can be stable in a random potential for a suitable weak-repulsive limit of a dense Bose gas, even though the non-interacting case is pathological. The condensate exists primarily because the interactions allow screening of the random potential. This may happen even when the chemical potential is in the Lifshitz tails of the single-particle case. Indeed, we argue that there are no Lifshitz tail states in our dense but weakly-interacting system. Using a number-phase representation, we calculate the increase in the depletion of the condensate with increasing randomness (at fixed density) which indicates the eventual destruction of the condensed phase-perhaps to a localized phase. The physical picture discussed should be relevant to the understanding of helium thin films