19,896 research outputs found
Range Analysis of Binaries with Minimal Effort
COTS components are ubiquitous in military, industrial and governmental systems. However, the bene?fits of reduced development and maintainance costs are compromised by security concerns. Since source code is unavailable, security audits necessarily occur at the binary level. Push-button formal method techniques, such as model checking and abstract interpretation, can support this process by, among other things, inferring ranges of values for registers. Ranges aid the security engineer in checking for vulnerabilities that relate, for example, to integer wrapping, uninitialised variables and bu?er over ows. Yet the lack of structure in binaries limits the e?ffectiveness of classical range analyses based on widening. This paper thus contributes a simple but novel range analysis, formulated in terms of linear programming, which calculates ranges without manual intervention
Rightsizing LISA
The LISA science requirements and conceptual design have been fairly stable
for over a decade. In the interest of reducing costs, the LISA Project at NASA
has looked for simplifications of the architecture, at downsizing of
subsystems, and at descopes of the entire mission. This is a natural activity
of the formulation phase, and one that is particularly timely in the current
NASA budgetary context. There is, and will continue to be, enormous pressure
for cost reduction from both ESA and NASA, reviewers and the broader research
community. Here, the rationale for the baseline architecture is reviewed, and
recent efforts to find simplifications and other reductions that might lead to
savings are reported. A few possible simplifications have been found in the
LISA baseline architecture. In the interest of exploring cost sensitivity, one
moderate and one aggressive descope have been evaluated; the cost savings are
modest and the loss of science is not.Comment: To be published in Classical and Quantum Gravity; Proceedings of the
Seventh International LISA Symposium, Barcelona, Spain, 16-20 Jun. 2008; 10
pages, 1 figure, 3 table
Matched filtering of gravitational waves from inspiraling compact binaries: Computational cost and template placement
We estimate the number of templates, computational power, and storage
required for a one-step matched filtering search for gravitational waves from
inspiraling compact binaries. These estimates should serve as benchmarks for
the evaluation of more sophisticated strategies such as hierarchical searches.
We use waveform templates based on the second post-Newtonian approximation for
binaries composed of nonspinning compact bodies in circular orbits. We present
estimates for six noise curves: LIGO (three configurations), VIRGO, GEO600, and
TAMA. To search for binaries with components more massive than 0.2M_o while
losing no more than 10% of events due to coarseness of template spacing,
initial LIGO will require about 1*10^11 flops (floating point operations per
second) for data analysis to keep up with data acquisition. This is several
times higher than estimated in previous work by Owen, in part because of the
improved family of templates and in part because we use more realistic (higher)
sampling rates. Enhanced LIGO, GEO600, and TAMA will require computational
power similar to initial LIGO. Advanced LIGO will require 8*10^11 flops, and
VIRGO will require 5*10^12 flops. If the templates are stored rather than
generated as needed, storage requirements range from 1.5*10^11 real numbers for
TAMA to 6*10^14 for VIRGO. We also sketch and discuss an algorithm for placing
the templates in the parameter space.Comment: 15 pages, 4 figures, submitted to Phys. Rev.
Sources of radiation from neutron stars
I give a brief introduction to the problem of detecting gravitational
radiation from neutron stars. After a review of the mechanisms by which such
stars may produce radiation, I consider the different search strategies
appropriate to the different kinds of sources: isolated known pulsars, neutron
stars in binaries, and unseen neutron stars. The problem of an all-sky survey
for unseen stars is the most taxing one that we face in analysing data from
interferometers. I describe the kinds of hierarchical methods that are now
being investigated to reach the maximal sensitivity, and I suggest a
replacement for standard Fourier-transform search methods that requires fewer
floating-point operations for Fourier-based searches over large parameter
spaces, and in addition is highly parallelizable, working just as well on a
loosely coupled network of workstations as on a tightly coupled parallel
computer.Comment: 11 pages, no figure
An Overview of LISA Data Analysis Algorithms
The development of search algorithms for gravitational wave sources in the
LISA data stream is currently a very active area of research. It has become
clear that not only does difficulty lie in searching for the individual
sources, but in the case of galactic binaries, evaluating the fidelity of
resolved sources also turns out to be a major challenge in itself. In this
article we review the current status of developed algorithms for galactic
binary, non-spinning supermassive black hole binary and extreme mass ratio
inspiral sources. While covering the vast majority of algorithms, we will
highlight those that represent the state of the art in terms of speed and
accuracy.Comment: 21 pages. Invited highlight article appearing in issue 01 of
Gravitational Waves Notes, "GW Notes", edited by Pau Amaro-Seoane and Bernard
F. Schutz at: http://brownbag.lisascience.org/lisa-gw-notes
Comparisons of binary black hole merger waveforms
This a particularly exciting time for gravitational wave physics.
Ground-based gravitational wave detectors are now operating at a sensitivity
such that gravitational radiation may soon be directly detected, and recently
several groups have independently made significant breakthroughs that have
finally enabled numerical relativists to solve the Einstein field equations for
coalescing black-hole binaries, a key source of gravitational radiation. The
numerical relativity community is now in the position to begin providing
simulated merger waveforms for use by the data analysis community, and it is
therefore very important that we provide ways to validate the results produced
by various numerical approaches. Here, we present a simple comparison of the
waveforms produced by two very different, but equally successful
approaches--the generalized harmonic gauge and the moving puncture methods. We
compare waveforms of equal-mass black hole mergers with minimal or vanishing
spins. The results show exceptional agreement for the final burst of radiation,
with some differences attributable to small spins on the black holes in one
case.Comment: Revtex 4, 5 pages. Published versio
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