The Cuntz Algebra Q_N and C*-Algebras of Product Systems

We consider a product system over the multiplicative semigroup N^x of Hilbert bimodules which is implicit in work of S. Yamashita and of the second named author. We prove directly, using universal properties, that the associated Nica-Toeplitz algebra is an extension of the C^*-algebra Q_N introduced recently by Cuntz.Comment: 13 page

Large 2D Coulomb crystals in a radio frequency surface ion trap

We designed and operated a surface ion trap, with an ion-substrate distance of 500\mum, realized with standard printed-circuit-board techniques. The trap has been loaded with up to a few thousand Sr+ ions in the Coulomb-crystal regime. An analytical model of the pseudo-potential allowed us to determine the parameters that drive the trap into anisotropic regimes in which we obtain large (N>150) purely 2D ion Coulomb crystals. These crystals may open a simple and reliable way to experiments on quantum simulations of large 2D systems.Comment: 4 pages, 4 figure

Accurate 3D Cell Segmentation using Deep Feature and CRF Refinement

We consider the problem of accurately identifying cell boundaries and labeling individual cells in confocal microscopy images, specifically, 3D image stacks of cells with tagged cell membranes. Precise identification of cell boundaries, their shapes, and quantifying inter-cellular space leads to a better understanding of cell morphogenesis. Towards this, we outline a cell segmentation method that uses a deep neural network architecture to extract a confidence map of cell boundaries, followed by a 3D watershed algorithm and a final refinement using a conditional random field. In addition to improving the accuracy of segmentation compared to other state-of-the-art methods, the proposed approach also generalizes well to different datasets without the need to retrain the network for each dataset. Detailed experimental results are provided, and the source code is available on GitHub.Comment: 5 pages, 5 figures, 3 table

An ice giant exoplanet interpretation of the anomaly in microlensing event OGLE-2011-BLG-0173

We analyze the microlensing event OGLE-2011-BLG-0173, which shows a small perturbation at the end of the microlensing event caused by the primary lens. We consider both binary lens and binary source models and we explore their degeneracies, some of which have not previously been recognized. There are two families of binary lens solutions, one with a mass ratio $q\approx4\times10^{-4}$ and a separation s~4.6 and the other with q~0.015 and s~0.22, i.e, both have companions in the planetary regime. We search for solutions by using Bayesian analysis that includes planet frequency as a prior and find that the s~4.6 family is the preferred one with ~4 M_Uranus mass planet on an orbit of ~10 AU. The degeneracies arise from a paucity of information on the anomaly, demonstrating that high-cadence observations are essential for characterizing wide-orbit microlensing planets. Hence, we predict that the planned WFIRST microlensing survey will be less prone to these degeneracies than the ongoing ground-based surveys. We discuss the known low-mass, wide-orbit companions and we notice that for the largest projected separations the mass ratios are either high (consistent with brown dwarf companions) or low (consistent with Uranus analogs), but intermediate mass ratios (Jupiter analogs on wide orbits) have not been detected to date, despite the fact that the sensitivity to such planets should be higher than that of Uranus analogs. This is therefore tentative evidence of the existence of a massive ice giant desert at wide separations. On the other hand, given their low intrinsic detection sensitivity, Uranus analogs may be ubiquitous.Comment: AJ accepted, 6 figures, 4 table

Testing Causality Between Team Performance and Payroll: The Cases of Major League Baseball and English Soccer

The link between team payroll and competitive balance plays a central role in the theory of team sports but is seldom investigated empirically. This paper uses data on team payrolls in Major League Baseball between 1980 and 2000 to examine the link and implements Granger causality tests to establish whether the relationship runs from payroll to performance or vice versa. While there is no evidence that causality runs from payroll to performance over the entire sample period, the data shows that the cross section correlation between payroll and performance increased significantly in the 1990s. As a comparison, the paper examines the relationship between pay and performance in English soccer, and it is shown that Granger causality from higher payrolls to better performance cannot be rejected. We argue that this difference may be a consequence of the open market for player talent that obtains in soccer compared to the significant restrictions on trade that exist in Major League Baseball