Radiation recoil from highly distorted black holes

We present results from numerical evolutions of single black holes distorted by axisymmetric, but equatorially asymmetric, gravitational (Brill) waves. Net radiated energies, apparent horizon embeddings, and recoil velocities are shown for a range of Brill wave parameters, including both even and odd parity distortions of Schwarzschild black holes. We find that a wave packet initially concentrated on the black hole throat, a likely model also for highly asymmetric stellar collapse and late stage binary mergers, can generate a maximum recoil velocity of about 150 (23) km/sec for even (odd) parity perturbations, significantly less than that required to eject black holes from galactic cores.Comment: 15 pages, 8 figure

The Superspace of Geometrodynamics

Wheeler's Superspace is the arena in which Geometrodynamics takes place. I review some aspects of its geometrical and topological structure that Wheeler urged us to take seriously in the context of canonical quantum gravity.Comment: 29 pages, 8 figures. To appear in the Wheeler memorial volume of General Relativity and Gravitatio

Moving with the beat: heart rate and visceral temperature of free-swimming and feeding bluefin tuna

Owing to the inherent difficulties of studying bluefin tuna, nothing is known of the cardiovascular function of free-swimming fish. Here, we surgically implanted newly designed data loggers into the visceral cavity of juvenile southern bluefin tuna (Thunnus maccoyii) to measure changes in the heart rate (fH) and visceral temperature (TV) during a two-week feeding regime in sea pens at Port Lincoln, Australia. Fish ranged in body mass from 10 to 21 kg, and water temperature remained at 18–19°C. Pre-feeding fH typically ranged from 20 to 50 beats min−1. Each feeding bout (meal sizes 2–7% of tuna body mass) was characterized by increased levels of activity and fH (up to 130 beats min−1), and a decrease in TV from approximately 20 to 18°C as cold sardines were consumed. The feeding bout was promptly followed by a rapid increase in TV, which signified the beginning of the heat increment of feeding (HIF). The time interval between meal consumption and the completion of HIF ranged from 10 to 24 hours and was strongly correlated with ration size. Although fH generally decreased after its peak during the feeding bout, it remained elevated during the digestive period and returned to routine levels on a similar, but slightly earlier, temporal scale to TV. These data imply a large contribution of fH to the increase in circulatory oxygen transport that is required for digestion. Furthermore, these data oppose the contention that maximum fH is exceptional in bluefin tuna compared with other fishes, and so it is likely that enhanced cardiac stroke volume and blood oxygen carrying capacity are the principal factors allowing superior rates of circulatory oxygen transport in tuna