Pinning of stripes by local structural distortions in cuprate high-Tc superconductors

We study the spin-density wave (stripe) instability in lattices with mixed low-temperature orthorhombic (LTO) and low-temperature tetragonal (LTT) crystal symmetry. Within an explicit mean-field model it is shown how local LTT regions act as pinning centers for static stripe formation. We calculate the modulations in the local density of states near these local stripe regions and find that mainly the coherence peaks and the van Hove singularity (VHS) are spatially modulated. Lastly, we use the real-space approach to simulate recent tunneling data in the overdoped regime where the VHS has been detected by utilizing local normal state regions.Comment: Conference proceedings for Stripes1

The discrete-time H∞H_\infty control problem with measurement feedback

This paper is concerned with the discrete-time $H_\infty$ control problem with measurement feedback. We extend previous results by having weaker assumptions on the system parameters. We also show explicitly the structure of $H_\infty$ controllers. Finally, we show that it is in certain cases possible, without loss of performance, to reduce the dynamical order of the controllers

Test for entanglement using physically observable witness operators and positive maps

Motivated by the Peres-Horodecki criterion and the realignment criterion we develop a more powerful method to identify entangled states for any bipartite system through a universal construction of the witness operator. The method also gives a new family of positive but non-completely positive maps of arbitrary high dimensions which provide a much better test than the witness operators themselves. Moreover, we find there are two types of positive maps that can detect 2xN and 4xN bound entangled states. Since entanglement witnesses are physical observables and may be measured locally our construction could be of great significance for future experiments.Comment: 6 pages, 1 figure, revtex4 styl

Differential Geometry of Bipartite Quantum States

We investigate the differential geometry of bipartite quantum states. In particular the manifold structures of pure bipartite states are studied in detail. The manifolds with respect to all normalized pure states of arbitrarily given Schmidt ranks or Schmidt coefficients are explicitly presented. The dimensions of the related manifolds are calculated.Comment: 10 page

Competing Demands of Prosociality & Equity in Monkeys

Prosocial decisions may lead to unequal payoffs among group members. Although an aversion to inequity has been found in empirical studies of both human and nonhuman primates, the contexts previously studied typically do not involve a trade-off between pro-sociality and inequity. Here we investigate the apparent co-existence of these two factors, specifically the competing demands of prosociality and equity. We directly compare the responses of brown capuchin monkeys (Cebus apella) among situations where pro-social preferences conflict with equality, using a paradigm comparable to other studies of cooperation and inequity in this species. By choosing to pull a tray towards themselves, subjects rewarded themselves and/or another in conditions in which the partner either received the same or different rewards, or the subject received no reward. In unequal payoff conditions, subjects could obtain equality by choosing not to pull in the tray, so that neither individual was rewarded. The monkeys showed prosocial preferences even in situations of moderate disadvantageous inequity, preferring to pull in the tray more often when a partner was present than absent. However when the discrepancy between rewards increased, prosocial behavior ceased

Generation of defects and disorder from deeply quenching a liquid to form a solid

We show how deeply quenching a liquid to temperatures where it is linearly unstable and the crystal is the equilibrium phase often produces crystalline structures with defects and disorder. As the solid phase advances into the liquid phase, the modulations in the density distribution created behind the advancing solidification front do not necessarily have a wavelength that is the same as the equilibrium crystal lattice spacing. This is because in a deep enough quench the front propagation is governed by linear processes, but the crystal lattice spacing is determined by nonlinear terms. The wavelength mismatch can result in significant disorder behind the front that may or may not persist in the latter stage dynamics. We support these observations by presenting results from dynamical density functional theory calculations for simple one- and two-component two-dimensional systems of soft core particles.Comment: 25 pages, 11 figure

An efficient direct solver for a class of mixed finite element problems

In this paper we present an efficient, accurate and parallelizable direct method for the solution of the (indefinite) linear algebraic systems that arise in the solution of fourth-order partial differential equations (PDEs) using mixed finite element approximations. The method is intended particularly for use when multiple right-hand sides occur, and when high accuracy is required in these solutions. The algorithm is described in some detail and its performance is illustrated through the numerical solution of a biharmonic eigenvalue problem where the smallest eigenpair is approximated using inverse iteration after discretization via the Ciarlet–Raviart mixed finite element method

Experimental Investigation into the Influence of Backfill Types on the Vibro-acoustic Characteristics of Leaks in MDPE Pipe

Pipe leak location estimates are commonly conducted using Vibro-Acoustic Emission (VAE) based methods, usually using accelerometers or hydrophones. Successful estimation of a leak's location is dependent on a number of factors, including the speed of sound, resonance, backfill, reflections from other sources, leak shape and size. However, despite some investigation into some of the aforementioned factors, the influence of backfill type on a leak's VAE signal has still not been experimentally quantified. A limited number of studies have attempted to quantify the effects of backfill. However, all of these studies couple other variables which could be equally responsible for their observed changes in leak signal. There have been no controlled studies where one variable can be directly compared to one another (i.e. all variables remain constant, only changing backfill type). The aim of this paper is to better characterise the influence of backfill on a leak's VAE signal by individually isolating all variables. For the first time, this paper demonstrates the influence of backfill on leak VAE signal by keeping all other variables consistent. It was found that the backfill type had a strong influence on the frequency and amplitude of leak signals, which is likely to have a significant impact on the accuracy of leak location estimates

Curvature Based Biomarkers for Diabetic Retinopathy via Exponential Curve Fits in SE(2)

We propose a robust and fully automatic method for the analysis of vessel tortuosity. Our method does not rely on pre-segmentation of vessels, but instead acts directly on retinal image data. The method is based on theory of best-fit exponential curves in the roto-translation group SE(2). We lift 2D images to 3D functions called orientation scores by including an orientation dimension in the domain. In the extended domain of positions and orientations (identified with SE(2)) we study exponential curves, whose spatial projections have constant curvature. By locally fitting such curves to data in orientation scores, via our new iterative stabilizing refinement method, we are able to assign to each location a curvature and confidence value. These values are then used to define global tortuosity measures. The method is validated on synthetic and retinal images. We show that the tortuosity measures can serve as effective biomarkers for diabetes and different stages of diabetic retinopathy