54,767 research outputs found
Gravitational Waves
This article reviews current efforts and plans for gravitational-wave
detection, the gravitational-wave sources that might be detected, and the
information that the detectors might extract from the observed waves. Special
attention is paid to (i) the LIGO/VIRGO network of earth-based, kilometer-scale
laser interferometers, which is now under construction and will operate in the
high-frequency band ( to Hz), and (ii) a proposed
5-million-kilometer-long Laser Interferometer Space Antenna (LISA), which would
fly in heliocentric orbit and operate in the low-frequency band ( to
Hz). LISA would extend the LIGO/VIRGO studies of stellar-mass ( to
) black holes into the domain of the massive black holes
( to ) that inhabit galactic nuclei and quasars.Comment: Latex; 25 pages, 14 figures. Figures are in eps files that are
bundled together in a tarred, compressed, and uuencoded form; figures are
inserted into text via a "special" command rather than psfig or epsf. Uses a
style file "snow.sty" that is bundled with the figure
Low frequency electromagnetic radiation coming from gravitational waves generated by neutron stars
We investigate the possibility of observing very low frequency (VLF)
electromagnetic radiation produced from the vacuum by gravitational waves. We
review the calculations leading to the possibility of vacuum conversion of
gravitational waves into electromagnetic waves and show how this process evades
the well-known prohibition against particle production from gravitational
waves. Using Newman-Penrose scalars, we estimate the luminosity of this
proposed electromagnetic counterpart radiation coming from gravitational waves
produced by neutron star oscillations. The detection of electromagnetic
counterpart radiation would provide an indirect way of observing gravitational
radiation with future spacecraft missions, especially lunar orbiting probes.Comment: 16 pages revtex, no figures, 1 table. Version published in PR
Superluminal Gravitational Waves
The quantum gravity effects of vacuum polarization of gravitons propagating
in a curved spacetime cause the quantum vacuum to act as a dispersive medium
with a refractive index. Due to this dispersive medium gravitons acquire
superluminal velocities. The dispersive medium is produced by higher derivative
curvature contributions to the effective gravitational action. It is shown that
in a Friedmann-Lema\^{i}tre-Robertson-Walker spacetime in the early universe
near the Planck time , the speed of
gravitational waves , where and are the
speeds of gravitational waves and light today. The large speed of gravitational
waves stretches their wavelengths to super-horizon sizes, allowing them to be
observed in B-polarization experiments.Comment: 5 pages, no figure
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