182 research outputs found
The electrogravity transformation and global monopoles in scalar-tensor gravity
The electrogravity transformation is defined by an interchange of the
``active'' and ``passive'' electric parts of the Riemann tensor. Such a
transformation has been used to find new solutions that are ``dual'' to the
Kerr family of black hole spacetimes in general relativity. In such a case, the
dual solution is a similar black hole spacetime endowed with a global monopole
charge. Here, we extend this formalism to obtain solutions dual to the static,
spherically symmetric solutions of two different scalar-tensor gravity
theories. In particular, we first study the duals of the charged black hole
solutions of a four-dimensional low-energy effective action of heterotic string
theory. Next, we study dual of the Xanthopoulos-Zannias solution in Brans-Dicke
theory, which contains a naked singularity. We show that, analogous to general
relativity, in these scalar-tensor gravity theories the dual solutions are
similar to the original spacetimes, but with a global monopole charge.Comment: 15 pages, RevTe
On the Brown-York quasilocal energy, gravitational charge, and black hole horizons
We study a recently proposed horizon defining identity for certain black hole
spacetimes. It relates the difference of the Brown-York quasilocal energy and
the Komar charge at the horizon to the total energy of the spacetime. The
Brown-York quasilocal energy is evaluated for some specific choices of
spacetime foliations. With a certain condition imposed on the matter
distribution, we prove this identity for spherically symmetric static black
hole solutions of general relativity. For these cases, we show that the
identity can be derived from a Gauss-Codacci condition that any
three-dimensional timelike boundary embedded around the hole must obey. We also
demonstrate the validity of the identity in other cases by explicitly applying
it to several static, non-static, asymptotically flat, and asymptotically
non-flat black hole solutions. These include the asymptotically FRW solutions
and the case of a black hole with a global monopole charge.Comment: 13 pages, RevTex. To appear in Physical Review
A data-analysis strategy for detecting gravitational-wave signals from inspiraling compact binaries with a network of laser-interferometric detectors
A data-analysis strategy based on the maximum-likelihood method (MLM) is
presented for the detection of gravitational waves from inspiraling compact
binaries with a network of laser-interferometric detectors having arbitrary
orientations and arbitrary locations around the globe. The MLM is based on the
network likelihood ratio (LR), which is a function of eight signal-parameters
that determine the Newtonian inspiral waveform. In the MLM-based strategy, the
LR must be maximized over all of these parameters. Here, we show that it is
possible to maximize it analytically over four of the eight parameters.
Maximization over a fifth parameter, the time of arrival, is handled most
efficiently by using the Fast-Fourier-Transform algorithm. This allows us to
scan the parameter space continuously over these five parameters and also cuts
down substantially on the computational costs. Maximization of the LR over the
remaining three parameters is handled numerically. This includes the
construction of a bank of templates on this reduced parameter space. After
obtaining the network statistic, we first discuss `idealized' networks with all
the detectors having a common noise curve for simplicity. Such an exercise
nevertheless yields useful estimates about computational costs, and also tests
the formalism developed here. We then consider realistic cases of networks
comprising of the LIGO and VIRGO detectors: These include two-detector
networks, which pair up the two LIGOs or VIRGO with one of the LIGOs, and the
three-detector network that includes VIRGO and both the LIGOs. For these
networks we present the computational speed requirements, network
sensitivities, and source-direction resolutions.Comment: 40 pages, 2 figures, uses RevTex and psfig, submitted to Phys. Rev.
D, A few minor changes adde
- …