Hadron Systematics and Emergent Diquarks

We briefly review a variety of theoretical and phenomenological indications for the probable importance of powerful diquark correlations in hadronic physics. We demonstrate that the bulk of light hadron spectroscopy can be organized using three simple hypotheses: Regge-Chew-Frautschi mass formulae, feebleness of spin-orbit forces, and energetic distinctions among a few different diquark configurations. Those hypotheses can be implemented in a semi-classical model of color flux tubes, extrapolated down from large orbital angular momentum $L$. We discuss refinements of the model to include the effects of tunneling, mass loading, and internal excitations. We also discern effects of diquark correlations in observed patterns of baryon decays. Many predictions and suggestions for further work appear.Comment: 18 pages, 11 figures. Talk by FW at a workshop at Schloss Ringberg, October 2005. To appear in the Proceeding

Anomalous Currents on Closed Surfaces: Extended Proximity, Partial Quantization, and Qubits

Motivated by the surface of topological insulators, the Dirac anomaly's discontinuous dependence on sign of the mass, $m/|m|$, is investigated on closed topologies when mass terms are weak or only partially cover the surface. It is found that, unlike the massive Dirac theory on an infinite plane, there is a smoothly decreasing current when the mass region is not infinite; also, a massive finite region fails to exhibit a Hall current edge--exerting an extended proximity effect, which can, however, be uniformly small--and oppositely orientated Hall phases are fully quantized while accompanied by diffuse chiral modes. Examples are computed using Dirac energy eigenstates on a flat torus (genus one topology) and closed cap cylinder (genus zero topology) for various mass-term geometries. Finally, from the resulting the properties of the surface spectra, a potential application for a flux-charge qubit is presented.Comment: 22 pages, 13 figures. References and focus updated. Added effective action arguments. Same text as published versio

Diet selection by sheep in two moorland sites: chapel fell and Monk's moor

Not availabl

Continuation of Nesterov's Smoothing for Regression with Structured Sparsity in High-Dimensional Neuroimaging

Predictive models can be used on high-dimensional brain images for diagnosis of a clinical condition. Spatial regularization through structured sparsity offers new perspectives in this context and reduces the risk of overfitting the model while providing interpretable neuroimaging signatures by forcing the solution to adhere to domain-specific constraints. Total Variation (TV) enforces spatial smoothness of the solution while segmenting predictive regions from the background. We consider the problem of minimizing the sum of a smooth convex loss, a non-smooth convex penalty (whose proximal operator is known) and a wide range of possible complex, non-smooth convex structured penalties such as TV or overlapping group Lasso. Existing solvers are either limited in the functions they can minimize or in their practical capacity to scale to high-dimensional imaging data. Nesterov's smoothing technique can be used to minimize a large number of non-smooth convex structured penalties but reasonable precision requires a small smoothing parameter, which slows down the convergence speed. To benefit from the versatility of Nesterov's smoothing technique, we propose a first order continuation algorithm, CONESTA, which automatically generates a sequence of decreasing smoothing parameters. The generated sequence maintains the optimal convergence speed towards any globally desired precision. Our main contributions are: To propose an expression of the duality gap to probe the current distance to the global optimum in order to adapt the smoothing parameter and the convergence speed. We provide a convergence rate, which is an improvement over classical proximal gradient smoothing methods. We demonstrate on both simulated and high-dimensional structural neuroimaging data that CONESTA significantly outperforms many state-of-the-art solvers in regard to convergence speed and precision.Comment: 11 pages, 6 figures, accepted in IEEE TMI, IEEE Transactions on Medical Imaging 201

Two Nucleon-States in a Chiral Quark-Diquark Model

We study the ground and first excited states of nucleons in a chiral quark-diquark model. We include two quark-diquark channels of the scalar-isoscalar and axial-vector-isovector types for the nucleon states. The diquark correlation violating the spin-flavor SU(4)$_{SF}$ symmetry allows to treat the two quark-diquark channels independently. Hence the two states appear as the superpositions of the two quark-diquark channels; one is the nucleon and the other is a state which does not appear in the SU(4)$_{SF}$ quark models. With a reasonable choice of model parameters, the mass of the excited state appears at around 1.5 GeV, which we identify with the Roper resonance N(1440).Comment: 11 pages, 5 figures. Errors are corrected. Conclusions are not affecte

Pore-scale processes in tertiary low salinity waterflooding in a carbonate rock: Micro-dispersions, water film growth, and wettability change

HYPOTHESIS: The wettability change from oil-wet towards more water-wet conditions by injecting diluted brine can improve oil recovery from reservoir rocks, known as low salinity waterflooding. We investigated the underlying pore-scale mechanisms of this process to determine if improved recovery was associated with a change in local contact angle, and if additional displacement was facilitated by the formation of micro-dispersions of water in oil and water film swelling. EXPERIMENTS: X-ray imaging and high-pressure and temperature flow apparatus were used to investigate and compare high and low salinity waterflooding in a carbonate rock sample. The sample was placed in contact with crude oil to obtain an initial wetting state found in hydrocarbon reservoirs. High salinity brine was then injected at increasing flow rates followed by low salinity brine injection using the same procedure. FINDINGS: Development of water micro-droplets within the oil phase and detachment of oil layers from the rock surface were observed after low salinity waterflooding. During high salinity waterflooding, contact angles showed insignificant changes from the initial value of 115°, while the mean curvature and local capillary pressure values remained negative, consistent with oil-wet conditions. However, with low salinity, the decrease in contact angle to 102° and the shift in the mean curvature and capillary pressure to positive values indicate a wettability change. Overall, our analysis captured the in situ mechanisms and processes associated with the low salinity effect and ultimate increase in oil recovery