Electromagnetic Field in Higher-Dimensional Black-Hole Spacetimes

A special test electromagnetic field in the spacetime of the higher-dimensional generally rotating NUT-(A)dS black hole is found. It is adjusted to the hidden symmetries of the background represented by the principal Killing-Yano tensor. Such electromagnetic field generalizes the field of charged black hole in four dimensions. In higher dimensions, however, the gravitational back reaction of such a field cannot be consistently solved.Comment: 8 pages, no figures; presented at the Black hole VI conference in White Point, Canada, May 12-16 2007, and at the GRG18 conference in Sydney, Australia, July 8-13 200

Radio observations of NGC 6388: an upper limit on the mass of its central black hole

We present the results of deep radio observations with the Australia Telescope Compact Array (ATCA) of the globular cluster NGC 6388. We show that there is no radio source detected (with a r.m.s. noise level of 27 uJy) at the cluster centre of gravity or at the locations of the any of the Chandra X-ray sources in the cluster. Based on the fundamental plane of accreting black holes which is a relationship between X-ray luminosity, radio luminosity and black hole mass, we place an upper limit of 1500 M_sun on the mass of the putative intermediate-mass black hole located at the centre of NGC 6388. We discuss the uncertainties of this upper limit and the previously suggested black hole mass of 5700 M_sun based on surface density profile analysis.Comment: 6 pages, 2 figures, accepted for publication in MNRA

Distinguishing causal time from Minkowski time and a model for the black hole quantum eigenstates

A discussion is presented of the principle of black hole com- plementarity. It is argued that this principle could be viewed as a breakdown of general relativity, or alternatively, as the introduction of a time variable with multiple `sheets' or `branches' A consequence of the theory is that the stress-energy tensor as viewed by an outside observer is not simply the Lorentz-transform of the tensor viewed by an ingoing observer. This can serve as a justification of a new model for the black hole atmosphere, recently re-introduced. It is discussed how such a model may lead to a dynamical description of the black hole quantum states.Comment: Plenary Lecture Notes ICMP97, Brisbane, Australia, July 1997. 12 pages LaTeX, 5 Figures Postscrip

The Black Summer Bushfires in the Eurobodalla Shire; the Role of the Local Newspaper in Framing the Event and Experience

This thesis focuses on the Black Summer bushfires that occurred in the Eurobodalla Shire, which is located on the South Coast of New South Wales, Australia (NSW). The bushfires experienced in the Eurobodalla were a significant part of the devastating nation-wide bushfire season experienced across Australia, which has since become colloquially named as ‘Black Summer’. The Black Summer bushfires are the most recent of many other severe, ‘black’ bushfire events in Australia’s recorded history.1 Although Australia is familiar with severe bushfires due to its history, climate and ecology, the Black Summer bushfires have been labelled by mainstream media, politicians, and the Royal Commission into National Natural Disaster Arrangements (2021) as ‘unprecedented’, due to the extent and severity of these fires. The bushfires received not only national but international media attention, and countries such as America, New Zealand, Canada and Singapore came to aid Australia in their fight against the fires. The devastation caused by the Black Summer bushfires on communities like the Eurobodalla is immense, and at least momentarily, brought the topic of bushfire disasters in Australia to the forefront of public, media and political debate

Searching for a place to belong in a time of othering

Australia is a land of opportunity, where hard work can bring a better life. Most immigrants come to Australia to establish a new life and fulfil hopes and dreams for better life opportunities. Like many immigrants to Australia, I came to establish a new better life for myself and for family. In this paper, I share my challenges of being different, and of being black and the experiences of black Africans in Australia. The paper invites more conversations on finding ways forward to change the system that favours some and disadvantages others. It indicates the need to humanise the Other and make Australia a more inclusive and liveable multicultural environment

African black beetle in vineyards

The African black beetle, Heteronychus arator, is an important pest of horticultural crops, ornamentals and pastures in Western Australia. They also attack lawns and are commonly referred to as the black lawn beetle. This beetle was first recorded in Australia during the 1920s and originates from southern Africa where it is a major establishment pest of maize.https://researchlibrary.agric.wa.gov.au/bulletins/1144/thumbnail.jp

No Way Back: Maximizing survival time below the Schwarzschild event horizon

It has long been known that once you cross the event horizon of a black hole, your destiny lies at the central singularity, irrespective of what you do. Furthermore, your demise will occur in a finite amount of proper time. In this paper, the use of rockets in extending the amount of time before the collision with the central singularity is examined. In general, the use of such rockets can increase your remaining time, but only up to a maximum value; this is at odds with the ``more you struggle, the less time you have'' statement that is sometimes discussed in relation to black holes. The derived equations are simple to solve numerically and the framework can be employed as a teaching tool for general relativity.Comment: 7-pages, 5 figures, accepted for publication in the Publications of the Astronomical Society of Australia (Journal name corrected.

Limits on the quiescent radio emission from the black hole binaries GRO J1655-40 and XTE J1550-564

We present the results of radio observations of the black hole binaries GRO J1655-40 and XTE J1550-564 in quiescence, with the upgraded Australia Telescope Compact Array. Neither system was detected. Radio flux density upper limits (3 sigma) of 26 micro Jy (at 5.5 GHz), 47 micro Jy (at 9 GHz) for GRO J1655-40, and 1.4 mJy (at 1.75 GHz), 27 micro Jy (at 5.5 GHz), 47 micro Jy (at 9 GHz) for XTE J1550-564 were measured. In conjunction with quasi-simultaneous Chandra X-ray observations (in the case of GRO J1655-40) and Faulkes Telescope optical observations (XTE J1550-564) we find that these systems provide the first evidence of relatively `radio quiet' black hole binaries at low luminosities; indicating that the scatter observed in the hard state X-ray:radio correlation at higher luminosities may also extend towards quiescent levels.Comment: Accepted for publication in MNRA