York University

About: York University is a education organization based out in Toronto, Ontario, Canada. It is known for research contribution in the topics: Population & Politics. The organization has 18899 authors who have published 43357 publications receiving 1568560 citations.

Detection of orbital motions near the last stable circular orbit of the massive black hole SgrA

Abstract: We report the detection of continuous positional and polarization changes of the compact source SgrA* in high states (“flares”) of its variable near-infrared emission with the near-infrared GRAVITY-Very Large Telescope Interferometer (VLTI) beam-combining instrument. In three prominent bright flares, the position centroids exhibit clockwise looped motion on the sky, on scales of typically 150 μ as over a few tens of minutes, corresponding to about 30% the speed of light. At the same time, the flares exhibit continuous rotation of the polarization angle, with about the same 45(±15) min period as that of the centroid motions. Modelling with relativistic ray tracing shows that these findings are all consistent with a near face-on, circular orbit of a compact polarized “hot spot” of infrared synchrotron emission at approximately six to ten times the gravitational radius of a black hole of 4 million solar masses. This corresponds to the region just outside the innermost, stable, prograde circular orbit (ISCO) of a Schwarzschild–Kerr black hole, or near the retrograde ISCO of a highly spun-up Kerr hole. The polarization signature is consistent with orbital motion in a strong poloidal magnetic field.

Domain wall QCD with physical quark masses

Abstract: We present results for several light hadronic quantities (${f}_{\ensuremath{\pi}}$, ${f}_{K}$, ${B}_{K}$, ${m}_{ud}$, ${m}_{s}$, ${t}_{0}^{1/2}$, ${w}_{0}$) obtained from simulations of $2+1$ flavor domain wall lattice QCD with large physical volumes and nearly physical pion masses at two lattice spacings We perform a short, $\mathcal{O}(3)%$, extrapolation in pion mass to the physical values by combining our new data in a simultaneous chiral/continuum ``global fit'' with a number of other ensembles with heavier pion masses We use the physical values of ${m}_{\ensuremath{\pi}}$, ${m}_{K}$ and ${m}_{\mathrm{\ensuremath{\Omega}}}$ to determine the two quark masses and the scale---all other quantities are outputs from our simulations We obtain results with subpercent statistical errors and negligible chiral and finite-volume systematics for these light hadronic quantities, including ${f}_{\ensuremath{\pi}}=1302(9)\text{ }\text{ }\mathrm{MeV}$; ${f}_{K}=1555(8)\text{ }\text{ }\mathrm{MeV}$; the average up/down quark mass and strange quark mass in the $\overline{\mathrm{MS}}$ scheme at 3 GeV, 2997(49) and 8164(117) MeV respectively; and the neutral kaon mixing parameter, ${B}_{K}$, in the renormalization group invariant scheme, 0750(15) and the $\overline{\mathrm{MS}}$ scheme at 3 GeV, 0530(11)

Managerial Incentives and Corporate Fraud: The Sources of Incentives Matter

Abstract: Operating performance and stock return results imply that managers who commit fraud anticipate large stock price declines if they were to report truthfully, which would cause greater losses for managerial stockholdings than for options because of differences in convexity. Fraud firms have significantly greater incentives from unrestricted stockholdings than control firms do, and unrestricted stockholdings are their largest incentive source. Our results emphasize the importance of the shape and vesting status of incentive payoffs in providing incentives to commit fraud. Fraud firms also have characteristics that suggest a lower likelihood of fraud detection, which implies lower expected costs of fraud. Copyright 2009, Oxford University Press.

Warfarin Use and the Risk for Stroke and Bleeding in Patients With Atrial Fibrillation Undergoing Dialysis

Abstract: Background—Current observational studies on warfarin use and the risk for stroke and bleeding in patients with atrial fibrillation (AF) undergoing dialysis found conflicting results. Methods and Results—We conducted a population-based retrospective cohort study of patients aged ≥65 years admitted to a hospital with a primary or secondary diagnosis of AF, in Quebec and Ontario, Canada from 1998 to 2007. The AF cohort was grouped into dialysis (hemodialysis and peritoneal dialysis) and nondialysis patients and into warfarin and no-warfarin users according to the first prescription filled for warfarin within 30 days after AF hospital discharge. We determined the association between warfarin use and the risk for stroke and bleeding in dialysis and nondialysis patients. The cohort comprised 1626 dialysis patients and 204 210 nondialysis patients. Among dialysis patients, 46% (756/1626) patients were prescribed warfarin. Among dialysis patients, warfarin users had more congestive heart failure and diabetes mell...