4,188 research outputs found
Mapping the gravitational wave background
The gravitational wave sky is expected to have isolated bright sources
superimposed on a diffuse gravitational wave background. The background
radiation has two components: a confusion limited background from unresolved
astrophysical sources; and a cosmological component formed during the birth of
the universe. A map of the gravitational wave background can be made by
sweeping a gravitational wave detector across the sky. The detector output is a
complicated convolution of the sky luminosity distribution, the detector
response function and the scan pattern. Here we study the general
de-convolution problem, and show how LIGO (Laser Interferometric Gravitational
Observatory) and LISA (Laser Interferometer Space Antenna) can be used to
detect anisotropies in the gravitational wave background.Comment: 16 pages, 6 figures. Submitted to CQ
Applying coupon-collecting theory to computer-aided assessments
Computer-based tests with randomly generated questions allow a large number
of different tests to be generated. Given a fixed number of alternatives for
each question, the number of tests that need to be generated before all
possible questions have appeared is surprisingly low.Comment: 19 pages; bibliographic information added as follows. To appear in
Bingham, N. H., and Goldie, C. M. (eds), Probability and Mathematical
Genetics: Papers in Honour of Sir John Kingman. London Math. Soc. Lecture
Note Series. Cambridge: Cambridge Univ. Pres
Facing the LISA Data Analysis Challenge
By being the first observatory to survey the source rich low frequency region
of the gravitational wave spectrum, the Laser Interferometer Space Antenna
(LISA) will revolutionize our understanding of the Cosmos. For the first time
we will be able to detect the gravitational radiation from millions of galactic
binaries, the coalescence of two massive black holes, and the inspirals of
compact objects into massive black holes. The signals from multiple sources in
each class, and possibly others as well, will be simultaneously present in the
data. To achieve the enormous scientific return possible with LISA,
sophisticated data analysis techniques must be developed which can mine the
complex data in an effort to isolate and characterize individual signals. This
proceedings paper very briefly summarizes the challenges associated with
analyzing the LISA data, the current state of affairs, and the necessary next
steps to move forward in addressing the imminent challenges.Comment: 4 pages, no figures, Proceedings paper for the TeV Particle
Astrophysics II conference held Aug 28-31 at the Univ. of Wisconsi
Forward Modeling of Space-borne Gravitational Wave Detectors
Planning is underway for several space-borne gravitational wave observatories
to be built in the next ten to twenty years. Realistic and efficient forward
modeling will play a key role in the design and operation of these
observatories. Space-borne interferometric gravitational wave detectors operate
very differently from their ground based counterparts. Complex orbital motion,
virtual interferometry, and finite size effects complicate the description of
space-based systems, while nonlinear control systems complicate the description
of ground based systems. Here we explore the forward modeling of space-based
gravitational wave detectors and introduce an adiabatic approximation to the
detector response that significantly extends the range of the standard low
frequency approximation. The adiabatic approximation will aid in the
development of data analysis techniques, and improve the modeling of
astrophysical parameter extraction.Comment: 14 Pages, 14 Figures, RevTex
I Have Been Somewhere: Place In The South Carolina Poems Of Nikky Finney And Kwame Dawes
The following thesis focuses on the role of “place” in the poems of two black South Carolinian poets, Nikky Finney and Kwame Dawes. Borrowing from cultural and humanistic geographers’ myriad understandings of place, as well as philosophers’, I examine the ways in which Finney’s Rice and Dawes’s Wisteria function as meditations on and transmutations of the South Carolina low country in both its physical and non-physical dimensions, ultimately shedding light on historically silenced and marginalized emplaced realities. I also examine how Finney and Dawes employ different strategies of emplacement and their influence on the poems’ structure and meaning. In the final chapter of my thesis, I put my own emplaced poems in conversation with Finney’s and Dawes’s, and I further analyze my creative process and product to understand more deeply the range of choices available to poets interested in poetry of emplacement
Gravity Waves, Chaos, and Spinning Compact Binaries
Spinning compact binaries are shown to be chaotic in the Post-Newtonian
expansion of the two body system. Chaos by definition is the extreme
sensitivity to initial conditions and a consequent inability to predict the
outcome of the evolution. As a result, the spinning pair will have
unpredictable gravitational waveforms during coalescence. This poses a
challenge to future gravity wave observatories which rely on a match between
the data and a theoretical template.Comment: Final version published in PR
Comment on "Gravity Waves, Chaos, and Spinning Compact Binaries"
In this comment, I argue that chaotic effects in binary black hole inspiral
will not strongly impact the detection of gravitational waves from such
systems.Comment: 1 page, comment on gr-qc/991004
LISA data analysis I: Doppler demodulation
The orbital motion of the Laser Interferometer Space Antenna (LISA) produces
amplitude, phase and frequency modulation of a gravitational wave signal. The
modulations have the effect of spreading a monochromatic gravitational wave
signal across a range of frequencies. The modulations encode useful information
about the source location and orientation, but they also have the deleterious
affect of spreading a signal across a wide bandwidth, thereby reducing the
strength of the signal relative to the instrument noise. We describe a simple
method for removing the dominant, Doppler, component of the signal modulation.
The demodulation reassembles the power from a monochromatic source into a
narrow spike, and provides a quick way to determine the sky locations and
frequencies of the brightest gravitational wave sources.Comment: 5 pages, 7 figures. References and new comments adde
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