Universal analytic properties of noise. Introducing the J-Matrix formalism

We propose a new method in the spectral analysis of noisy time-series data for damped oscillators. From the Jacobi three terms recursive relation for the denominators of the Pad\'e Approximations built on the well-known Z-transform of an infinite time-series, we build an Hilbert space operator, a J-Operator, where each bound state (inside the unit circle in the complex plane) is simply associated to one damped oscillator while the continuous spectrum of the J-Operator, which lies on the unit circle itself, is shown to represent the noise. Signal and noise are thus clearly separated in the complex plane. For a finite time series of length 2N, the J-operator is replaced by a finite order J-Matrix J_N, having N eigenvalues which are time reversal covariant. Different classes of input noise, such as blank (white and uniform), Gaussian and pink, are discussed in detail, the J-Matrix formalism allowing us to efficiently calculate hundreds of poles of the Z-transform. Evidence of a universal behaviour in the final statistical distribution of the associated poles and zeros of the Z-transform is shown. In particular the poles and zeros tend, when the length of the time series goes to infinity, to a uniform angular distribution on the unit circle. Therefore at finite order, the roots of unity in the complex plane appear to be noise attractors. We show that the Z-transform presents the exceptional feature of allowing lossless undersampling and how to make use of this property. A few basic examples are given to suggest the power of the proposed method.Comment: 14 pages, 8 figure

Two-photon quantum walks in an elliptical direct-write waveguide array

Integrated optics provides an ideal test bed for the emulation of quantum systems via continuous-time quantum walks. Here we study the evolution of two-photon states in an elliptic array of waveguides. We characterise the photonic chip via coherent-light tomography and use the results to predict distinct differences between temporally indistinguishable and distinguishable two-photon inputs which we then compare with experimental observations. Our work highlights the feasibility for emulation of coherent quantum phenomena in three-dimensional waveguide structures.Comment: 8 pages, 7 figure

Facebook's Mobile Career

At the end of its first decade, Facebook’s identity, popularity, and characteristics are shaped in important ways by its becoming a form of mobile media, as much as it as platform associated with Internet and social media. This paper seeks to explore and understand Facebook as the important force in mobile media and communication it now is. It draws upon and combines perspectives from technology production, design, and economy, as well as user adoption, consumption, practices, affect, emotion, and resistance. The paper discusses the beginnings of mobile Facebook, and the early adoption of mobile Facebook associated with the rise of smartphones. The second part of the paper explores Facebook’s integration with photography (with Instagram) and social games (such as Zynga’s Farmville). The paper argues that Facebook’s mobile career is an accomplishment that has distinctively melded evolving affordances, everyday use across a wide range of settings, as well as political economies, corporate strategy, and design.Australian Research Counci

A burst search for gravitational waves from binary black holes

Compact binary coalescence (CBC) is one of the most promising sources of gravitational waves. These sources are usually searched for with matched filters which require accurate calculation of the GW waveforms and generation of large template banks. We present a complementary search technique based on algorithms used in un-modeled searches. Initially designed for detection of un-modeled bursts, which can span a very large set of waveform morphologies, the search algorithm presented here is constrained for targeted detection of the smaller subset of CBC signals. The constraint is based on the assumption of elliptical polarisation for signals received at the detector. We expect that the algorithm is sensitive to CBC signals in a wide range of masses, mass ratios, and spin parameters. In preparation for the analysis of data from the fifth LIGO-Virgo science run (S5), we performed preliminary studies of the algorithm on test data. We present the sensitivity of the search to different types of simulated CBC waveforms. Also, we discuss how to extend the results of the test run into a search over all of the current LIGO-Virgo data set.Comment: 12 pages, 4 figures, 2 tables, submitted for publication in CQG in the special issue for the conference proceedings of GWDAW13; corrected some typos, addressed some minor reviewer comments one section restructured and references updated and correcte

Challenging Perceptions of Disability through Performance Poetry Methods: The "Seen but Seldom Heard" Project.

This paper considers performance poetry as a method to explore lived experiences of disability. We discuss how poetic inquiry used within a participatory arts-based research framework can enable young people to collectively question society’s attitudes and actions towards disability. Poetry will be considered as a means to develop a more accessible and effective arena in which young people with direct experience of disability can be empowered to develop new skills that enable them to tell their own stories. Discussion of how this can challenge audiences to critically reflect upon their own perceptions of disability will also be developed

Phenomenological template family for black-hole coalescence waveforms

Recent progress in numerical relativity has enabled us to model the non-perturbative merger phase of the binary black-hole coalescence problem. Based on these results, we propose a phenomenological family of waveforms which can model the inspiral, merger, and ring-down stages of black hole coalescence. We also construct a template bank using this family of waveforms and discuss its implementation in the search for signatures of gravitational waves produced by black-hole coalescences in the data of ground-based interferometers. This template bank might enable us to extend the present inspiral searches to higher-mass binary black-hole systems, i.e., systems with total mass greater than about 80 solar masses, thereby increasing the reach of the current generation of ground-based detectors.Comment: Minor changes, Submitted to Class. Quantum Grav. (Proc. GWDAW11

Upper Limits on a Stochastic Background of Gravitational Waves

The Laser Interferometer Gravitational-Wave Observatory has performed a third science run with much improved sensitivities of all three interferometers. We present an analysis of approximately 200 hours of data acquired during this run, used to search for a stochastic background of gravitational radiation. We place upper bounds on the energy density stored as gravitational radiation for three different spectral power laws. For the flat spectrum, our limit of Ω_0<8.4×10^(-4) in the 69–156 Hz band is ~10^5 times lower than the previous result in this frequency range

Disability activism in the new media ecology: campaigning strategies in the digital era

This article examines the changing nature of disability activism through the influence of social media. As disabled people in the UK have been subjected to acute austerity, this has coincided with a new era of disability activism channelled through increased social media participation. Drawing on the analysis of one group's online activities and a qualitative content analysis of disability protest coverage in traditional news media during the 2012 Paralympic Games, this article positions this shift in the broader framework of ‘new media ecology’ (Hoskins and O’Loughlin, 2010). We explore how emerging structures of disability activism have begun to offer a more visible profile to challenge government policy and negative stereotypes of disabled people. This highlights the usefulness of campaigning strategies for generating favourable news coverage for disability protest

The 'Iron Cage' strengthened? Discretion and digital discipline

Research on changes in public administration associated with the adoption and use of information and communication technologies ('informatization'), almost univocally supports the conclusion that shop floor discretion disappears under their influence. We, however, are ill at ease with this direction in thought about discretion. Our unease is based on the scholarly work about practices, organizational learning and responsiveness. In this article, we test the thesis on the relation between informatization and operational discretion in an empirical research of operational discretion and informatization in two Dutch public agencies, both large and both automated. Our findings show that informatization does not destroy operational discretion, but rather obscures discretion. Based on the work of Argyris, we show that the phenomenon at work is 'participatory boundary practices', the direct personal ties that keep an organization together. ICTs destroy such links and thereby affect organizational learning. © Blackwell Publishing Ltd. 2007

Status of NINJA: the Numerical INJection Analysis project

The 2008 NRDA conference introduced the Numerical INJection Analysis project (NINJA), a new collaborative effort between the numerical relativity community and the data analysis community. NINJA focuses on modeling and searching for gravitational wave signatures from the coalescence of binary system of compact objects. We review the scope of this collaboration and the components of the first NINJA project, where numerical relativity groups shared waveforms and data analysis teams applied various techniques to detect them when embedded in colored Gaussian noise