Coherent Control of Quantum Chaotic Diffusion

Extensive coherent control over quantum chaotic diffusion using the kicked rotor model is demonstrated and its origin in deviations from random matrix theory is identified. Further, the extent of control in the presence of external decoherence is established. The results are relevant to both areas of quantum chaos and coherent control.Comment: 4 pages, 4 figures, to appear in Phys. Rev. Let

Quantum signatures of chaos in the dynamics of a trapped ion

We show how a nonlinear chaotic system, the parametrically kicked nonlinear oscillator, may be realised in the dynamics of a trapped, laser-cooled ion, interacting with a sequence of standing wave pulses. Unlike the original optical scheme [G.J.Milburn and C.A.Holmes, Phys. Rev A, 44, p4704, (1991)], the trapped ion enables strongly quantum dynamics with minimal dissipation. This should permit an experimental test of one of the quantum signatures of chaos; irregular collapse and revival dynamics of the average vibrational energy.Comment: 9 pages, 9 Postscript figures, Revtex, submitted to Phys. Rev.

Bridging the gap between low and high mass dwarf galaxies

While the dark matter content within the most massive giant and smallest dwarf galaxies has been probed -- spanning a range of over one million in mass -- an important observational gap remains for galaxies of intermediate mass. This gap covers K band magnitudes of approximately -16 > M_K > -18 (for which dwarf galaxies have B--K ~ 2). On the high mass side of the gap are dwarf elliptical (dE) galaxies, that are dominated by stars in their inner regions. While the low mass side includes dwarf spheroidal (dSph) galaxies that are dark matter-dominated and ultra compact dwarf (UCD) objects that are star-dominated. Evolutionary pathways across the gap have been suggested but remain largely untested because the `gap' galaxies are faint, making dynamical measurements very challenging. With long exposures on the Keck telescope using the ESI instrument we have succeeded in bridging this gap by measuring the dynamical mass for five dwarf galaxies with M_K ~ -17.5 (M_B ~ --15.5). With the exception of our brightest dwarf galaxy, they possess relatively flat velocity dispersion profiles of around 20 km/s. By examining their 2D scaling relations and 3D fundamental manifold, we found that the sizes and velocity dispersions of these gap galaxies reveal continuous trends from dE to dSph galaxies. We conclude that low-luminosity dwarf elliptical galaxies are dominated by stars, not by dark matter, within their half light radii. This finding can be understood if internal feedback processes are operating most efficiently in gap galaxies, gravitationally heating the centrally-located dark matter to larger radii. Whereas external environmental processes, which can strip away stars, have a greater influence on dSph galaxies resulting in their higher dark matter fractions. Abridged.Comment: 20 pages, includes 12 figures, accepted for publication in MNRA

Analytical expressions for the deprojected Sersic model

The Sersic model has become the standard to parametrize the surface brightness distribution of early-type galaxies and bulges of spiral galaxies. A major problem is that the deprojection of the Sersic surface brightness profile to a luminosity density cannot be executed analytically for general values of the Sersic index. Mazure & Capelato (2002) used the Mathematica computer package to derive an expression of the Sersic luminosity density in terms of the Meijer G function for integer values of the Sersic index. We generalize this work using analytical means and use Mellin integral transforms to derive an exact, analytical expression for the luminosity density in terms of the Fox H function for all values of the Sersic index. We derive simplified expressions for the luminosity density, cumulative luminosity and gravitational potential in terms of the Meijer G function for all rational values of the Sersic index and we investigate their asymptotic behaviour at small and large radii. As implementations of the Meijer G function are nowadays available both in symbolic computer algebra packages and as high-performance computing code, our results open up the possibility to calculate the density of the Sersic models to arbitrary precision.Comment: 9 pages, accepted for publication in Astronomy and Astrophysic

A comparison of Qatari and Chinese cadet table tennis players: analysis of Asian championship team competition

Video analysis was performed during the Asian Cadet Table Tennis Championships to determine playing style and patterns of top and lower ranked nations. China and Qatar were chosen for analysis based on their performance during the tournament (1st/2nd playoff and 7th/8th playoff respectively). Notational analysis techniques were implemented to analyze 3 matches for each nation. Significant (p<0.05) differences were identified in serve and return placement and shot choice. Chinese players used a higher proportion of long return placement and a higher percentage of topspin shots compared to Qatari players. This preliminary study suggests that at cadet level, Chinese players exhibit a more attacking style of play than Qatari players

Implications for physical preparation of cadet male table tennis players: analysis of the 2013 championship singles final

The purpose of this case-study was to attain and describe data on the physical demands placed on elite Asian cadet male table tennis players in high-level competition. The 2013 Asian cadet singles final was notated live while the match was video recorded for further post-analysis. A typical point consisted of 4-5 shots with the player activated for 3.2 s, working for 3.3 s and resting for 17.8 s on average. The frequency of movement types was reported and typical footwork patterns were described for the most common movement types observed (step, linear jump, lateral jump and pivot). Typical footwork sequences were presented for the first two movements when serving and returning. This information could be used to inform a strength and conditioning programme for a developing cadet player seeking to replicate a playing style of an elite Asian cadet player

Notational analysis of the cadet and junior singles table tennis finals at the 2013 Asian championship

The purpose of this paper was to provide a comparison between the two finals of the elite cadet and junior table tennis players. The 2013 Asian singles cadet and junior final matches were notated live and video recorded for further post-analysis. Junior players demonstrated a more variable serve placement strategy and favored the more aggressive topspin cross table return deep into the oppositions forehand. Work rate time was marginally greater per game in the junior finals (cadet vs. junior; 3.1s ± 1.7 3.3s ± 1.8) however junior players had a greater average rally length (5.3 s ± 2.6 and 4.4 ± 0.9) and greater number of high velocity top spin shots (21.5 ± 5.5 and 14.9 ± 5.6). Physicality and aggressive playing style increases with both age and ability level. These data provide a start to inform coaches of the progression between the top levels at both age groups

The possibility of a metal insulator transition in antidot arrays induced by an external driving

It is shown that a family of models associated with the kicked Harper model is relevant for cyclotron resonance experiments in an antidot array. For this purpose a simplified model for electronic motion in a related model system in presence of a magnetic field and an AC electric field is developed. In the limit of strong magnetic field it reduces to a model similar to the kicked Harper model. This model is studied numerically and is found to be extremely sensitive to the strength of the electric field. In particular, as the strength of the electric field is varied a metal -- insulator transition may be found. The experimental conditions required for this transition are discussed.Comment: 6 files: kharp.tex, fig1.ps fig2.ps fi3.ps fig4.ps fig5.p

Bulk perturbations of N=2 branes

The evolution of supersymmetric A-type D-branes under the bulk renormalization group flow between two different N=2 minimal models is studied. Using the Landau-Ginzburg description we show that a specific set of branes decouples from the infrared theory, and we make detailed predictions for the behavior of the remaining branes. The Landau-Ginzburg picture is then checked against a direct conformal field theory analysis. In particular we construct a natural index pairing which is preserved by the RG flow, and show that the branes that decouple have vanishing index with the surviving branes.Comment: 35 pages (30 pages plus title and references), 8 figure

A Numerical Investigation of the Effects of Classical Phase Space Structure on a Quantum System

We present a detailed numerical study of a chaotic classical system and its quantum counterpart. The system is a special case of a kicked rotor and for certain parameter values possesses cantori dividing chaotic regions of the classical phase space. We investigate the diffusion of particles through a cantorus; classical diffusion is observed but quantum diffusion is only significant when the classical phase space area escaping through the cantorus per kicking period greatly exceeds Planck's constant. A quantum analysis confirms that the cantori act as barriers. We numerically estimate the classical phase space flux through the cantorus per kick and relate this quantity to the behaviour of the quantum system. We introduce decoherence via environmental interactions with the quantum system and observe the subsequent increase in the transport of quantum particles through the boundary.Comment: 15 pages, 22 figure