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Relativistic Flows in Astrophysics
1. 1 Schematic Picture of AGN Some galaxies are known to emit radiation with extremely high luminosities from a rather small volume in the ??ray, X-ray and UV continuum. Such active cores are the so-called Active Galactic Nuclei (AGN) and the radiation is commonly believed to be a result of gravitational energy released by matter spiraling around 9 a supermassive central black hole of about 10 M (see Fig. 1). Though the central engine which produces the enormous observed activity cannot be resolved observationally, a standard picture of an AGN has gradually emerged to explain the richness of the radiation spectra: • an accretion disk with radius from about 2 to 100 gravitational radii, R , g feeding the central black hole and emitting mainly in the UV and soft X-rays; • the broad line optically emitting clouds (BLR), which seem to be absent in 3 some sources (e. g. FRI, see hereafter) and extend up to a few 10 R from g the center.
Flash!
The origin and nature of gamma-ray bursts is currently one of the greatest mysteries in astrophysics. These tremendously powerful blasts produce more energy in a fraction of a second than our Sun does in ten billion years. Since their accidental discovery by American spy satellites over thirty years ago, astronomers have striven to understand these enigmatic explosions. It is only recently, thanks to an Italian-Dutch satellite, and powerful telescopes both on the ground and in space, that the mystery is beginning to be unravelled. Astronomers now realise that gamma-ray bursts are probably related to the birth of black holes in extremely distant galaxies. Flash! describes the fast moving field of gamma ray burst research, from the initial detection right up to the most recent discoveries. Based on interviews with leading scientists, this exciting book provides an inside view of the scientific challenges involved in unravelling the mystery of gamma-ray bursts.
Assessing the Impacts of Changes in the Information Technology R&D Ecosystem
The U.S. information technology (IT) research and development (R&D) ecosystem was the envy of the world in 1995. However, this position of leadership is not a birthright, and it is now under pressure. In recent years, the rapid globalization of markets, labor pools, and capital flows have encouraged many strong national competitors. During the same period, national policies have not sufficiently buttressed the ecosystem, or have generated side effects that have reduced its effectiveness. As a result, the U.S. position in IT leadership today has materially eroded compared with that of prior decades, and the nation risks ceding IT leadership to other nations within a generation. Assessing the Impacts of Changes in the Information Technology R&D Ecosystem calls for a recommitment to providing the resources needed to fuel U.S. IT innovation, to removing important roadblocks that reduce the ecosystem's effectiveness in generating innovation and the fruits of innovation, and to becoming a lead innovator and user of IT. The book examines these issues and makes recommendations to strengthen the U.S. IT R&D ecosystem.
Lament for America
Lament for America explores the major challenges to the status of the United States as a world superpower. In delving into the fundamental question of whether or not a relative decline is inevitable, the author recognizes that the changes faced over the next few decades will be more rapid and transformational than at any other period in American history. Lament for America offers concrete recommendations for renewal in areas such as defense policy, health care, education, and the environment, and serves as a useful guide to understanding how decisions will shape both the U.S. and global landscapes.
Is American Science in Decline?
Alarmists argue that the United States urgently needs more and better-trained scientists to compete with the rest of the world. Their critics counter that, far from facing a shortage, we are producing a glut of young scientists with poor employment prospects. Both camps have issued reports in recent years that predict the looming decline of American science. Drawing on their extensive analysis of national data sets, Yu Xie and Alexandra Killewald have welcome news to share: American science is in good health. Is American Science in Decline? does reveal areas of concern, namely scientists’ low earnings, the increasing competition they face from Asia, and the declining number of doctorates w...
Health and Inequality
This volume contains methodological and empirical research on the measurement and causes of health inequality from leading experts in health economics and economic inequality. It is essential reading for researchers working on health inequality and provides an immediate reconnaissance of the frontiers for those entering this exciting field.
Cosmic Explosions
The diversity of stellar death is revealed in the energy, velocity and geometry of the explosion debris ("ejecta''). Using multi-wavelength observations of gamma-ray burst (GRB) afterglows I show that GRBs, arising from the death of massive stars, are marked by relativistic, collimated ejecta ("jets'') with a wide range of opening angles. These results suggest that various cosmic explosions are powered by a common energy source, an "engine'' (possibly an accreting stellar-mass black hole), with their diverse appearances determined solely by the variable high velocity output. On the other hand, using radio observations I show that local type Ibc core-collapse supernovae generally lack relativ...
Ripples in Spacetime
A spacetime appetizer -- Relatively speaking -- Einstein on trial -- Wave talk and bar fights -- The lives of stars -- Clockwork precision -- Laser quest -- The path to perfection -- Creation stories -- Cold case -- Gotcha -- Black magic -- Nanoscience -- Follow-up questions -- Space invaders -- Surf's up for Einstein wave astronomy
Extreme Explosions
What happens at the end of the life of massive stars? At one time we thought all these stars followed similar evolutionary paths. However, new discoveries have shown that things are not quite that simple. This book focuses on the extreme –the most intense, brilliant and peculiar– of astronomical explosions. It features highly significant observational finds that push the frontiers of astronomy and astrophysics, particularly as before these objects were only predicted in theory. This book is for those who want the latest information and ideas about the most dramatic and unusual explosions detected by current supernova searches. It examines and explains cataclysmic and unusual events in stellar astrophysics and presents them in a non-mathematical but highly detailed way that non-professionals can understand and enjoy.
Too Small to Fail
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