Microscopic Approach to Shear Viscosities in Superfluid Gases: From BCS to BEC

We compute the shear viscosity, $\eta$, at general temperatures $T$, in a BCS-BEC crossover scheme which is demonstrably consistent with conservation laws. The study of $\eta$ is important because it constrains microscopic theories by revealing the excitation spectra. The onset of a normal state pairing gap and the contribution from pair degrees of freedom imply that $\eta$ at low $T$ becomes small, rather than exhibiting the upturn predicted by most others. Using the local density approximation, we find quite reasonable agreement with just-published experiments.Comment: 4 pages, 2 figure

The Kolmogorov-Smirnov test and its use for the identification of fireball fragmentation

We propose an application of the Kolmogorov-Smirnov test for rapidity distributions of individual events in ultrarelativistic heavy ion collisions. The test is particularly suitable to recognise non-statistical differences between the events. Thus when applied to a narrow centrality class it could indicate differences between events which would not be expected if all events evolve according to the same scenario. In particular, as an example we assume here a possible fragmentation of the fireball into smaller pieces at the quark/hadron phase transition. Quantitative studies are performed with a Monte Carlo model capable of simulating such a distribution of hadrons. We conclude that the Kolmogorov-Smirnov test is a very powerful tool for the identification of the fragmentation process.Comment: 9 pages, 10 figure

EFFECTS OF STEP LENGTH ON THE BIOMECHANICS OF LOWER LIMBS DURING ELLIPTICAL EXERCISE

Elliptical exercise (EE) has been developed as a low-impact aerobic exercise modality with increased popularity in fitness training and clinical applications over the last decade. During EE, the feet are constrained by pedals to follow an elliptical trajectory, with the possibility of producing disadvantageous joint loads and potential musculoskeletal overuse injuries (Lu et al., 2007). Therefore, proper selection of step length during EE may be helpful for the reduction of these disadvantageous joint loads. The purpose of the study was to study the effects of three different step lengths on biomechanics of the lower limbs during EE

Generating scalable graph states in an atom-nanophotonic interface

Scalable graph states are essential for measurement-based quantum computation and many entanglement-assisted applications in quantum technologies. Generation of these multipartite entangled states requires a controllable and efficient quantum device with delicate design of generation protocol. Here we propose to prepare high-fidelity and scalable graph states in one and two dimensions, which can be tailored in an atom-nanophotonic cavity via state carving technique. We propose a systematic protocol to carve out unwanted state components, which facilitates scalable graph states generations via adiabatic transport of a definite number of atoms in optical tweezers. An analysis of state fidelity is also presented, and the state preparation probability can be optimized via multiqubit state carvings and sequential single-photon probes. Our results showcase the capability of an atom-nanophotonic interface for creating graph states and pave the way toward novel problem-specific applications using scalable high-dimensional graph states with stationary qubits.Comment: 5 figures with supplemental materia

Quantum Anomalous Hall Effect in Hg1−y_{1-y}Mny_{y}Te Quantum Wells

The quantum Hall effect is usually observed when the two-dimensional electron gas is subjected to an external magnetic field, so that their quantum states form Landau levels. In this work we predict that a new phenomenon, the quantum anomalous Hall effect, can be realized in Hg$_{1-y}$Mn$_{y}$Te quantum wells, without the external magnetic field and the associated Landau levels. This effect arises purely from the spin polarization of the $Mn$ atoms, and the quantized Hall conductance is predicted for a range of quantum well thickness and the concentration of the $Mn$ atoms. This effect enables dissipationless charge current in spintronics devices.Comment: 5 pages, 3 figures. For high resolution figures see final published version when availabl

On the steady-state harmonic performance of subsea power cables used in offshore power generation schemes.

This thesis reports upon investigations undertaken into the electrical performance of high power subsea transmission cables and is specifically focused upon their harmonic behaviour, an understanding of which is fundamental for developing accurate computer based models to evaluate the performance of existing or new offshore generation schemes. A comprehensive literature search has been undertaken in the areas of offshore generation, offshore power transmission schemes and harmonic performance of subsea cable systems. Subsea cable configurations, types and anatomy are presented to give an appreciation of the arrangement of subsea power cables. Mathematical equations and computer based algorithms have been developed to model subsea transmission system behaviour where the electrical parameters derived from natural physical phenomena such as skin effects, proximity effects and mutual couplings are included. Proximity effect is examined to determine the consequences of whether it needs to be considered for each subsea cable arrangement. Bonding solutions for subsea transmission are investigated to study the effect they have on resonance frequency and harmonic response for different cable lengths. The resulting analysis for various cable arrangements explains how geometric arrangements affect the harmonic impedance and harmonic resonance. The harmonic distortion in HVAC offshore transmission systems is also studied to demonstrate the importance of considering all power components in a subsea power transmission system for harmonic evaluation. In addition, the harmonic distortions of the VSC- HVDC link and associated harmonic power loss are examined. The effects of switching frequency, smoothing capacitor bank size, cable materials and transmission method on harmonic performances of the VSC-HVDC system with varying cable lengths is discussed and therefore subsea power cable harmonic behaviour interacted with subsea transmission systems is investigated. The novel contribution of this work is claimed to be in the development of superior models of subsea cables, transmission schemes and associated performance studies, which should lead to significant improvements over existing models and their results