Spectral Characteristic Evolution: A New Algorithm for Gravitational Wave Propagation

We present a spectral algorithm for solving the full nonlinear vacuum Einstein field equations in the Bondi framework. Developed within the Spectral Einstein Code (SpEC), we demonstrate spectral characteristic evolution as a technical precursor to Cauchy Characteristic Extraction (CCE), a rigorous method for obtaining gauge-invariant gravitational waveforms from existing and future astrophysical simulations. We demonstrate the new algorithm's stability, convergence, and agreement with existing evolution methods. We explain how an innovative spectral approach enables a two orders of magnitude improvement in computational efficiency.Comment: 28 pages, 9 figure

Spectral Cauchy Characteristic Extraction of strain, news and gravitational radiation flux

We present a new approach for the Cauchy-characteristic extraction of gravitational radiation strain, news function, and the flux of the energy-momentum, supermomentum and angular momentum associated with the Bondi-Metzner-Sachs asymptotic symmetries. In Cauchy-characteristic extraction, a characteristic evolution code takes numerical data on an inner worldtube supplied by a Cauchy evolution code, and propagates it outwards to obtain the space-time metric in a neighborhood of null infinity. The metric is first determined in a scrambled form in terms of coordinates determined by the Cauchy formalism. In prior treatments, the waveform is first extracted from this metric and then transformed into an asymptotic inertial coordinate system. This procedure provides the physically proper description of the waveform and the radiated energy but it does not generalize to determine the flux of angular momentum or supermomentum. Here we formulate and implement a new approach which transforms the full metric into an asymptotic inertial frame and provides a uniform treatment of all the radiation fluxes associated with the asymptotic symmetries. Computations are performed and calibrated using the Spectral Einstein Code (SpEC).Comment: 30 pages, 17 figure

Slow light with flat or offset band edges in multi-mode fiber with two gratings

We consider mode coupling in multimode optical fibers using either two Bragg gratings or a Bragg grating and a long-period grating. We show that the magnitude of the band edge curvature can be controlled leading to a flat, quartic band-edge or to two band edges at distinct, nonequivalent $k$-values, allowing precise control of slow light propagation.Comment: 6 pages, 3 figure

Community bushfire safety: A review of post-black Saturday research

Following the 'Black Saturday' bushfires of 7 February 2009, a number of research reports on community bushfire safety were presented to the Victorian Bushfires Royal Commission. These include reports from the CFA, OESC, Bushfire CRC and Department of Justice. These reports have different research aims and employ a range of methods and samples. Some reports investigate community safety issues during the Black Saturday bushfires, while others examine preparedness and intentions for future fires. This paper reviews these reports to identify common findings, inconsistencies and gaps relating to community safety during bushfires, and discusses the implications of methodological differences for research findings

After 'Black Saturday': adapting to bushfires in a changing climate

Abstract not availabl

Vulnerability to bushfires in rural Australia: a case study from East Gippsland, Victoria

This paper investigates the nature and causes of vulnerability to bushfires in the Wulgulmerang district of East Gippsland, Victoria, in south-eastern Australia. In 2003 bushfires devastated the small population of this isolated farming district, destroying homes, agricultural assets and public infrastructure. The ?res also adversely affected the health, livelihoods and social lives of many local people. The paper examines: (i) how and why people were exposed to hazards during the bushfires; and (ii) how and why people were differentially capable of coping and adapting to the fires' impacts. Qualitative methods were primarily used to investigate these questions, including semi-structured interviews with residents and landholders of the district and others who responded to the fires in an official or unofficial capacity. Vulnerability is shown to arise from the circumstances of people's everyday lives, which are shaped by factors both within and beyond their control. Local pressures and challenges such as drought, declining farm incomes, depopulation, and the inaccessibility of essential services e are shown to increase people's exposure to hazards and reduce their capacities to cope and adapt. The paper demonstrates the fundamental importance of sustainable livelihoods and regional economic vitality to the long-term goal of vulnerability reduction

Examining bushfire policy in action: Preparedness and behaviour in the 2009 Black Saturday fires

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.An important part of reducing the risk of disaster is the preparedness of the people at risk. Australian bushfire authorities have policies and publicity about what households should do to be prepared - which include knowledge about fire risk, awareness of one's own risk, taking specific steps to reduce risk including having an emergency plan. Yet, there is sparse empirical evidence about the link between preparedness and actual behaviour in the face of a major disaster.The authors had an opportunity to examine the circumstances surrounding the 172 civilian fatalities which occurred in the 2009 Victorian 'Black Saturday' bushfires, through the examination of a detailed fatality dataset compiled by the Victorian Bushfires Royal Commission. This dataset allows detailed examination of Victorian bushfire safety policy ('Stay or go') in action on a day of extreme fire danger: from preparedness (both before and on the day of the fire) to behaviour on the day of the fire itself.This analysis presents three overarching findings. First, some aspects of 'Stay or go' appear to be supported: being well-prepared to evacuate remains the safest option in a bushfire; sheltering passively is very dangerous. Second, successful implementation of 'Stay or go' depends on a multitude of factors, which can challenge even the most capable householders. Third, events like Black Saturday challenge the 'Stay or go' approach, and indicate the need for a different approach on extreme fire danger days. We conclude by reflecting on the findings from this research in terms of the most recent changes to bushfire policy in Victoria.The project was funded by the Victorian Bushfires Royal Commission through the Bushfire Cooperative Research Centre. The Commission was involved in the project in an oversight capacity, in particular to ensure that strict confidence was maintained, and that conflicts of interest were avoided. Writing of this paper was supported through Saffron O’Neill’s ESRC Fellowship (S/K001175/1)

Changing the rules of the game: mechanisms that shape responsibility-sharing from beyond Australian fire and emergency management

In this paper, we look beyond Australian fire and emergency management to compare ways that responsibility-sharing - broadly conceived - has occurred in other places and sectors where risks to community safety are faced. Responsibility-sharing occurs any time there is collective action, and formal and informal institutions provide the 'rules of the game' that prescribe how responsibility should be shared amongst the parties involved. We reviewed a broad sample of risk research literature in order to examine by what mechanisms responsibility-sharing institutions have been shaped in other places and sectors where risks to community safety are faced. Our review revealed more alternatives for shaping responsibilitysharing institutions than are widely considered by policy and decision makers in Australian fire and emergency management. It therefore raises an important question about why certain mechanisms are chosen, prioritised, overlooked or resisted in this sector. An alternative way of conceiving and pursuing shared responsibility is also discussed