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Authors: Matthew J. Benacquista, Lee Samuel Finn, Shane L. Larson, Louis J. Rubbo

Date: Wed, 21 Jun 2006

Abstract: The principal goal of the \emph{LISA Science Analysis Workshop} is to encourage the development and maturation of science analysis technology in preparation for LISA science operations. Exactly because LISA is a pathfinder for a new scientific discipline -- gravitational wave astronomy -- LISA data processing and science analysis methodologies are in their infancy and require considerable maturation if they are to be ready to take advantage of LISA data. Here we offer some thoughts, in anticipation of the LISA Science Analysis Workshop, on analysis research problems that demonstrate the capabilities of different proposed analysis methodologies and, simultaneously, help to push those techniques toward greater maturity. Particular emphasis is placed on formulating questions that can be turned into well-posed problems involving tests run on specific data sets, which can be shared among different groups to enable the comparison of techniques on a well-defined platform.

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Authors: Reinhard Prix

Date: Tue, 20 Jun 2006

Abstract: We derive the parameter-space metric of the multi-detector F-statistic, which is the optimal detection statistic for continuous gravitational waves in stationary Gaussian noise. We find that there is a family of F-statistic metrics, parametrized by the (unknown) amplitude parameters. We explicitly derive the maximal mismatch-range of this metric family, and we introduce a corresponding "average" F-metric. We show that the multi-detector metric consists of noise-weighted averages of single-detector contributions, which implies that the number of templates required to cover the parameter space does not scale with the number of detectors. Contrary to using a longer observation time, combining more detectors (of similar sensitivity) is therefore the computationally cheapest way to improve the sensitivity of a coherent wide-parameter search for continuous gravitational waves. We explicitly compute the F-statistic metric (family) for signals from isolated spinning neutron stars, and we evaluate the quality of different metric approximations in a Monte-Carlo study. We also compare the metric predictions to the measured mismatches and identify two regimes in which the metric is not a good description of the parameter-space structure.

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Authors: Tania Regimbau, José Antonio de Freitas Pacheco

Date: Tue, 6 Jun 2006

Abstract: We investigate the gravitational wave background produced by magnetars. The statistical properties of these highly magnetized stars were derived by population synthesis methods and assumed to be also representative of extragalactic objects. The adopted ellipticity was calculated from relativistic models using equations of state and assumptions concerning the distribution of currents in the neutron star interior. The maximum amplitude occurs around 1.2 kHz, corresponding to $\Omega_{gw} \sim 10ˆ{-9}$ for a type I superconducting neutron star model. The expected signal is a continuous background that could mask the cosmological contribution produced in the early stage of the Universe.

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Authors: Manuel Luna, Alicia M. Sintes

Date: Tue, 6 Jun 2006

Abstract: We analyze the problem of parameter estimation for compact binary systems that could be detected by ground-based gravitational wave detectors.
So far this problem has only been dealt with for the inspiral and the ringdown phases separately. In this paper, we combine the information from both signals, and we study the improvement in parameter estimation, at a fixed signal-to-noise ratio, by including the ringdown signal without making any assumption on the merger phase. The study is performed for both initial and advanced LIGO and VIRGO detectors.

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Authors: Luc Blanchet

Date: Tue, 6 Jun 2006

Abstract: The modified Newtonian dynamics (MOND) has been proposed as an alternative to the dark matter paradigm; the philosophy behind is that there is no dark matter and we witness a violation of the Newtonian law of dynamics. In this Letter, we interpret differently the phenomenology sustaining MOND, as resulting from an effect of "gravitational polarization", of some cosmic fluid made of dipole moments, aligned in the gravitational field, and representing a new form of dark matter. We invoke an internal force, of non-gravitational origin, in order to hold together the microscopic constituents of the dipole. The dipolar particles are weakly influenced by the distribution of ordinary matter; they are accelerated not by the gravitational field, but by its gradient, or tidal gravitational field.

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