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Hayama K.,Japan National Astronomical Observatory | Hayama K.,Albert Einstein Institute Max Planck Institute For Gravitationsphysik | Nishizawa A.,Kyoto University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

The observation of gravitational waves with a global network of interferometric detectors such as advanced LIGO, advanced Virgo, and KAGRA will make it possible to probe into the nature of space-time structure. Besides Einstein's general theory of relativity, there are several theories of gravitation that passed experimental tests so far. The gravitational-wave observation provides a new experimental test of alternative theories of gravity because a gravitational wave may have at most six independent modes of polarization whose properties and number of modes are dependent on theories of gravity. This paper develops a method to reconstruct an arbitrary number of modes of polarization in time-series data of an advanced detector network. The method does not rely on any specific model, which gives a model-independent test of alternative theories of gravity. © 2013 American Physical Society.


Hild S.,University of Glasgow | Leavey S.,University of Glasgow | Graf C.,Albert Einstein Institute Max Planck Institute For Gravitationsphysik | Sorazu B.,University of Glasgow
IEEE Transactions on Smart Grid | Year: 2014

In this article we describe our efforts of extending demand-side control concepts to the application in portable electronic devices, such as laptop computers, mobile phones and tablet computers. As these devices feature built-in energy storage (in the form of batteries) and the ability to run complex control routines, they are well-suited for the implementation of smart charging concepts. We developed simple hardware and software based prototypes of smart charging controllers for a laptop computer that steer the charging process depending on the frequency of the electricity grid and in case of the software implementation also based on the battery charge status. If similar techniques are incorporated into millions of devices in UK households, this can contribute significantly to the stability of the electricity grid, help to mitigate the short-term power production fluctuations from renewable energy sources and avoid the high cost of building and maintaining conventional power plants as standby reserve. © 2013 IEEE.


Dent T.,Albert Einstein Institute Max Planck Institute For Gravitationsphysik | Dent T.,Leibniz University of Hanover | Veitch J.,Albert Einstein Institute Max Planck Institute For Gravitationsphysik
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

We revisit the problem of searching for gravitational waves from inspiralling compact binaries in Gaussian colored noise. If the intrinsic parameters of a quasicircular, nonprecessing binary are known, then the optimal statistic for detecting the dominant mode signal in a single interferometer is given by the well-known two-phase matched filter. However, the matched filter signal-to-noise ratio (SNR) is not in general an optimal statistic for an astrophysical population of signals, since their distribution over the intrinsic parameters will almost certainly not mirror that of noise events, which is determined by the (Fisher) information metric. Instead, the optimal statistic for a given astrophysical distribution will be the Bayes factor, which we approximate using the output of a standard template matched filter search. We then quantify the improvement in number of signals detected for various populations of nonspinning binaries: for a distribution of signals uniformly distributed in volume and with component masses distributed uniformly over the range 1≤m1,2/M?≤24, (m1+m2)/M?≤25 at fixed expected SNR, we find ?20% more signals at a false alarm threshold of 10-6Hz in a single detector. The method may easily be generalized to binaries with nonprecessing spins. © 2014 American Physical Society.

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