42,627 research outputs found
Strong-field tidal distortions of rotating black holes: III. Embeddings in hyperbolic 3-space
In previous work, we developed tools for quantifying the tidal distortion of
a black hole's event horizon due to an orbiting companion. These tools use
techniques which require large mass ratios (companion mass much smaller
than black hole mass ), but can be used for arbitrary bound orbits, and for
any black hole spin. We also showed how to visualize these distorted black
holes by embedding their horizons in a global Euclidean 3-space,
. Such visualizations illustrate interesting and important
information about horizon dynamics. Unfortunately, we could not visualize black
holes with spin parameter : such holes cannot
be globally embedded into . In this paper, we overcome this
difficulty by showing how to embed the horizons of tidally distorted Kerr black
holes in a hyperbolic 3-space, . We use black hole perturbation
theory to compute the Gaussian curvatures of tidally distorted event horizons,
from which we build a two-dimensional metric of their distorted horizons. We
develop a numerical method for embedding the tidally distorted horizons in
. As an application, we give a sequence of embeddings into
of a tidally interacting black hole with spin . A
small amplitude, high frequency oscillation seen in previous work shows up
particularly clearly in these embeddings.Comment: 10 pages, 6 figure
The University of Michigan Centimeter-Band All Stokes Blazar Monitoring Program: Single-Dish Polarimetry as a Probe of Parsec-Scale Magnetic Fields
The University of Michigan 26-m paraboloid was dedicated to obtaining linear
polarization and total flux density observations of blazars from the mid-1960s
until June 2012 providing an unprecedented record tracking centimeter-band
variability over decades at 14.5, 8.0, and 4.8 GHz for both targeted objects
and members of flux-limited samples. In the mid-1970s through the mid-1980s,
and during the last decade of the program, observations were additionally
obtained of circular polarization for a small sample of radio-bright (S>5Jy),
active sources. Key program results include evidence supporting class-dependent
differences in the magnetic field geometry of BL Lac and QSO jets,
identification of linear polarization changes temporally associated with flux
outbursts supporting a shock-in-jet scenario, and determination of the spectral
evolution of the Stokes V amplitude and polarity for testing proposed models.
Recent radiative transfer modeling during large flares supports a jet scenario
with a kinetically-dominated, relativistic flow at parsec scales with embedded
turbulent magnetic fields and dynamically-weak ordered components which may be
helical; the circular polarization observations are consistent with
linear-to-circular mode conversion within this turbulent jet environment.Comment: 8 pages, 4 figures, Proceedings of the conference "Polarised Emission
from Astrophysical Jets", June 12-16, 2017, Ierapetra, Greece, eds. E.
Angelakis, M. Boettcher, and J.-L. Gome
Swath Mapping on the Continental Shelf and Slope: The Eel River Basin, Northern California
First Paragraph
The STRATAFORM program sponsored by the Office of Naval Research (Nittrouer and Kravitz, 1996, this issue) seeks to understand how sedimentary processes lead to the formation of the stratigraphic sequences on continental margins. A central challenge facing this effort is to understand the transport of sediments in shore-parallel as well as shore-perpendicular directions• Multidimensionality is necessary to describe, for example, the accumulation of sediments from river inputs, the distribution of gullies and canyons on the slope, the meandering of channels, and the structure of slumps and slides
Constraints on Blazar Jet Conditions During Gamma-Ray Flaring from Radiative Transfer Modeling
As part of a program to investigate jet flow conditions during GeV gamma-ray
flares detected by Fermi, we are using UMRAO multi-frequency, centimeter-band
total flux density and linear polarization monitoring observations to constrain
radiative transfer models incorporating propagating shocks orientated at an
arbitrary angle to the flow direction. We describe the characteristics of the
model, illustrate how the data are used to constrain the models, and present
results for three program sources with diverse characteristics: PKS 0420-01, OJ
287, and 1156+295. The modeling of the observed spectral behavior yields
information on the sense, strength and orientation of the shocks producing the
radio-band flaring; on the energy distribution of the radiating particles; and
on the observer's viewing angle with respect to the jet independent of VLBI
data. We present evidence that, while a random component dominates the jet
magnetic field, a distinguishing feature of those radio events with an
associated gamma-ray flare is the presence of a weak but non-negligible ordered
magnetic field component along the jet axis.Comment: 6 pages, 4 figures. To appear in the proceedings of "The Innermost
Regions of Relativistic Jets and Their Magnetic Fields", Granada, Spai
Sexual Orientation Differences in the Relationship Between Victimization and Hazardous Drinking Among Women in the National Alcohol Survey
This study examined relationships between past experiences of victimization (sexual abuse and physical abuse in childhood, sexual abuse and physical abuse in adulthood, and lifetime victimization) and hazardous drinking among sexual minority women compared to exclusively heterosexual women. Data were from 11,169 women responding to sexual identity and sexual behavior questions from three National Alcohol Survey waves: 2000 (n = 3,880), 2005 (n = 3,464), and 2010 (n = 3,825). A hazardous drinking index was constructed from five dichotomous variables (5+ drinking in the past year, drinking two or more drinks daily, drinking to intoxication in the past year, two or more lifetime dependence symptoms, and two or more lifetime drinking-related negative consequences). Exclusively heterosexual women were compared with three groups of sexual minority women: lesbian, bisexual, and women who identified as heterosexual but reported same-sex partners. Each of the sexual minority groups reported significantly higher rates of lifetime victimization (59.1% lesbians, 76% bisexuals, and 64.4% heterosexual women reporting same-sex partners) than exclusively heterosexual women (42.3%). Odds for hazardous drinking among sexual minority women were attenuated when measures of victimization were included in the regression models. Sexual minority groups had significantly higher odds of hazardous drinking, even after controlling for demographic and victimization variables: lesbian (OR [sub]adj[sub] = 2.0, CI = 1.1–3.9, p \u3c .01; bisexual (OR [sub]adj[sub] = 1.8, CI = 1.0–3.3, p \u3c .05; heterosexual with same-sex partners (ORadj = 2.7; CI = 1.7–4.3, p \u3c .001). Higher rates of victimization likely contribute to, but do not fully explain, higher rates of hazardous drinking among sexual minority women. (PsycINFO Database Record (c) 2013 APA, all rights reserved) (journal abstract)
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