60 research outputs found
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
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
Constraining dark matter halo profiles and galaxy formation models using spiral arm morphology. II. Dark and stellar mass concentrations for 13 nearby face-on galaxies
We investigate the use of spiral arm pitch angles as a probe of disk galaxy
mass profiles. We confirm our previous result that spiral arm pitch angles (P)
are well correlated with the rate of shear (S) in disk galaxy rotation curves.
We use this correlation to argue that imaging data alone can provide a powerful
probe of galactic mass distributions out to large look-back times. We then use
a sample of 13 galaxies, with Spitzer 3.6-m imaging data and observed
H rotation curves, to demonstrate how an inferred shear rate coupled
with a bulge-disk decomposition model and a Tully-Fisher-derived velocity
normalization can be used to place constraints on a galaxy's baryon fraction
and dark matter halo profile. Finally we show that there appears to be a trend
(albeit a weak correlation) between spiral arm pitch angle and halo
concentration. We discuss implications for the suggested link between
supermassive black hole (SMBH) mass and dark halo concentration, using pitch
angle as a proxy for SMBH mass.Comment: 14 pages, 6 figures. Accepted for publication in the Astrophysical
Journa
- …