Controversies in the History of the Radiation Reaction problem in General Relativity

This paper examines the historical controversy over whether gravitationally bound systems, such as binary stars, experienced orbital damping due to the emission of gravitational radiation, focusing especially on the period of the 1950s, but also discussing the work of Einstein and Rosen in the 1930s on cylindrical gravitational waves and the later quadrupole formula controversy.Comment: 33 pages, Late

Relativistic Lighthouses: The Role of the Binary Pulsar in proving the existence of Gravitational Waves

This paper discusses the role of the discovery and analysis of the first binary pulsar in settling the long-running quadrupole formula controversy over the status of gravitational waves as a prediction of general relativity. It also discusses how we should understand the resolution of this controversy in the context of the so-called science wars. In other words it discusses whether concepts such as interpretive flexibility and the experimenters' regress can shed light on what can also be seen as a classical confirmation of realist expectations, in which a theoretical controversy is settled by a conclusive experiment.Comment: 28 pages, no figures, presented at a 1998 conference in Mainz on the History of General Relativit

Zoom and whirl: Eccentric equatorial orbits around spinning black holes and their evolution under gravitational radiation reaction

We study eccentric equatorial orbits of a test-body around a Kerr black hole under the influence of gravitational radiation reaction. We have adopted a well established two-step approach: assuming that the particle is moving along a geodesic (justifiable as long as the orbital evolution is adiabatic) we calculate numerically the fluxes of energy and angular momentum radiated to infinity and to the black hole horizon, via the Teukolsky-Sasaki-Nakamura formalism. We can then infer the rate of change of orbital energy and angular momentum and thus the evolution of the orbit. The orbits are fully described by a semilatus rectum p and an eccentricity e. We find that while, during the inspiral, e decreases until shortly before the orbit reaches the separatrix of stable bound orbits [which is defined by p(s)(e)], in many astrophysically relevant cases the eccentricity will still be significant in the last stages of the inspiral. In addition, when a critical value p(crit)(e) is reached, the eccentricity begins to increase as a result of continued radiation induced inspiral. The two values p(s), p(crit) (for given e) move closer to each other, in coordinate terms, as the black hole spin is increased, as they do also for fixed spin and increasing eccentricity. Of particular interest are moderate and high eccentricity orbits around rapidly spinning black holes, with p(e)approximate top(s)(e). We call these "zoom-whirl" orbits, because of their characteristic behavior involving several revolutions around the central body near periastron. Gravitational waveforms produced by such orbits are calculated and shown to have a very particular signature. Such signals may well prove of considerable astrophysical importance for the future Laser Interferometer Space Antenna detector

Controversies in the History of the Radiation Reaction Problem in General Relativity

Beginning in the early 1950s, experts in the theory of general relativity debated vigorously whether the theory predicted the emission of gravitational radiation from binary star systems. For a time, doubts also arose on whether gravitational waves could carry any energy. Since radiation phenomena have played a key role in the development of 20th century field theories, it is the main purpose of this paper to examine the reasons for the growth of scepticism regarding radiation in the case of the gravitational field. Although the focus is on the period from the mid-1930s to about 1960, when the modern study of gravitational waves was developing, some attention is also paid to the more recent and unexpected emergence of experimental data on gravitational waves which considerably sharpened the debate on certain controversial aspects of the theory of gravity waves. I analyze the use of the earlier history as a rhetorical device in review papers written by protagonists of the "quadrupole formula controversy" in the late 1970s and early 1980s. I argue that relativists displayed a lively interest in the historical background to the problem and exploited their knowledge of the literature to justify their own work and their assessment of the contemporary state of the subject. This illuminates the role of a scientific field's sense of its own history as a mediator in scientific controversy

Identification of Outflows and Candidate Dual Active Galactic Nuclei in SDSS Quasars at z=0.8-1.6

We present a sample of 131 quasars from the Sloan Digital Sky Survey at redshifts 0.8<z<1.6 with double peaks in either of the high-ionization narrow emission lines [NeV]3426 or [NeIII]3869. These sources were selected with the intention of identifying high-redshift analogs of the z<0.8 active galactic nuclei (AGN) with double-peaked [OIII]5007 lines, which might represent AGN outflows or dual AGN. Lines of high-ionization potential are believed to originate in the inner, highly photoionized portion of the narrow line region (NLR), and we exploit this assumption to investigate the possible kinematic origins of the double-peaked lines. For comparison, we measure the [NeV]3426 and [NeIII]3869 double peaks in low-redshift (z<0.8) [OIII]-selected sources. We find that [NeV]3426 and [NeIII]3869 show a correlation between line-splitting and line-width similar to that of [OIII]5007 in other studies; and the velocity-splittings are correlated with the quasar Eddington ratio. These results suggest an outflow origin for at least a subset of the double-peaks, allowing us to study the high-ionization gas kinematics around quasars. However, we find that a non-neligible fraction of our sample show no evidence for an ionization stratification. For these sources, the outflow scenario is less compelling, leaving the dual AGN scenario as a viable possibility. Finally, we find that our sample shows an anti-correlation between the velocity-offset ratio and luminosity ratio of the components, which is a potential dynamical argument for the presence of dual AGN. Therefore, this study serves as a first attempt at extending the selection of candidate dual AGN to higher redshifts.Comment: 19 pages, 12 figures, accepted for publication in The Astrophysical Journa

Gravitational radiation timescales for extreme mass ratio inspirals

The capture and inspiral of compact stellar masses into massive black holes is an important source of low-frequency gravitational waves (with frequencies of ~1-100mHz), such as those that might be detected by the planned Laser Interferometer Space Antenna (LISA). Simulations of stellar clusters designed to study this problem typically rely on simple treatments of the black hole encounter which neglect some important features of orbits around black holes, such as the minimum radii of stable, non-plunging orbits. Incorporating an accurate representation of the orbital dynamics near a black hole has been avoided due to the large computational overhead. This paper provides new, more accurate, expressions for the energy and angular momentum lost by a compact object during a parabolic encounter with a non-spinning black hole, and the subsequent inspiral lifetime. These results improve on the Keplerian expressions which are now commonly used and will allow efficient computational simulations to be performed that account for the relativistic nature of the spacetime around the central black hole in the system.Comment: 19 pages, 4 figures. Changed in response to referee's report. Accepted for publication in Astrophysical Journa