2,226 research outputs found
Canonical Phase Space Formulation of Quasilocal General Relativity
We construct a Hamiltonian formulation of quasilocal general relativity using
an extended phase space that includes boundary coordinates as configuration
variables. This allows us to use Hamiltonian methods to derive an expression
for the energy of a non-isolated region of space-time that interacts with its
neighbourhood. This expression is found to be very similar to the Brown-York
quasilocal energy that was originally derived by Hamilton-Jacobi methods. We
examine the connection between the two formalisms and find that when the
boundary conditions for the two are harmonized, the resulting quasilocal
energies are identical.Comment: 31 pages, 2 figures, references added, typos corrected, section 3
revised for clarity, to appear in Classical and Quantum Gravit
The first law for slowly evolving horizons
We study the mechanics of Hayward's trapping horizons, taking isolated
horizons as equilibrium states. Zeroth and second laws of dynamic horizon
mechanics come from the isolated and trapping horizon formalisms respectively.
We derive a dynamical first law by introducing a new perturbative formulation
for dynamic horizons in which "slowly evolving" trapping horizons may be viewed
as perturbatively non-isolated.Comment: 4 pages, typos fixed, minor changes in wording for clarity, to appear
in PR
Searching for binary coalescences with inspiral templates: Detection and parameter estimation
There has been remarkable progress in numerical relativity recently. This has
led to the generation of gravitational waveform signals covering what has been
traditionally termed the three phases of the coalescence of a compact binary -
the inspiral, merger and ringdown. In this paper, we examine the usefulness of
inspiral only templates for both detection and parameter estimation of the full
coalescence waveforms generated by numerical relativity simulations. To this
end, we deploy as search templates waveforms based on the effective one-body
waveforms terminated at the light-ring as well as standard post-Newtonian
waveforms. We find that both of these are good for detection of signals.
Parameter estimation is good at low masses, but degrades as the mass of the
binary system increases.Comment: 14 pages, submitted to proceedings of the NRDA08 meeting, Syracuse,
Aug. 11-14, 200
A fully-coherent all-sky search for gravitational-waves from compact binary coalescences
We introduce a fully-coherent method for searching for gravitational wave
signals generated by the merger of black hole and/or neutron star binaries.
This extends the coherent analysis previously developed and used for targeted
gravitational wave searches to an all-sky, all-time search. We apply the search
to one month of data taken during the fifth science run of the LIGO detectors.
We demonstrate an increase in sensitivity of 25% over the coincidence search,
which is commensurate with expectations. Finally, we discuss prospects for
implementing and running a coherent search for gravitational wave signals from
binary coalescence in the advanced gravitational wave detector data.Comment: 17 pages, 12 figure
Improved source localization with LIGO India
A global network of advanced gravitational wave interferometric detectors is
under construction. These detectors will offer an order of magnitude
improvement in sensitivity over the initial detectors and will usher in the era
of gravitational wave astronomy. In this paper, we evaluate the benefits of
relocating one of the advanced LIGO detectors to India.Comment: 7 pages, 3 figures, accepted for publication in proceedings of
ICGC2011 conference. Localization figures update
Isolated, slowly evolving, and dynamical trapping horizons: geometry and mechanics from surface deformations
We study the geometry and dynamics of both isolated and dynamical trapping
horizons by considering the allowed variations of their foliating two-surfaces.
This provides a common framework that may be used to consider both their
possible evolutions and their deformations as well as derive the well-known
flux laws. Using this framework, we unify much of what is already known about
these objects as well as derive some new results. In particular we characterize
and study the "almost-isolated" trapping horizons known as slowly evolving
horizons. It is for these horizons that a dynamical first law holds and this is
analogous and closely related to the Hawking-Hartle formula for event horizons.Comment: 39 pages, 6 figures, version to appear in PRD : a few minor changes
and many typos corrected in equation
Distorted charged dilaton black holes
We construct exact static, axisymmetric solutions of Einstein-Maxwell-dilaton
gravity presenting distorted charged dilaton black holes. The thermodynamics of
such distorted black holes is also discussed.Comment: 14 pages, latex; v2 typos corrected, references adde
Comparison of Gravitational Wave Detector Network Sky Localization Approximations
Gravitational waves emitted during compact binary coalescences are a
promising source for gravitational-wave detector networks. The accuracy with
which the location of the source on the sky can be inferred from gravitational
wave data is a limiting factor for several potential scientific goals of
gravitational-wave astronomy, including multi-messenger observations. Various
methods have been used to estimate the ability of a proposed network to
localize sources. Here we compare two techniques for predicting the uncertainty
of sky localization -- timing triangulation and the Fisher information matrix
approximations -- with Bayesian inference on the full, coherent data set. We
find that timing triangulation alone tends to over-estimate the uncertainty in
sky localization by a median factor of for a set of signals from
non-spinning compact object binaries ranging up to a total mass of , and the over-estimation increases with the mass of the system. We
find that average predictions can be brought to better agreement by the
inclusion of phase consistency information in timing-triangulation techniques.
However, even after corrections, these techniques can yield significantly
different results to the full analysis on specific mock signals. Thus, while
the approximate techniques may be useful in providing rapid, large scale
estimates of network localization capability, the fully coherent Bayesian
analysis gives more robust results for individual signals, particularly in the
presence of detector noise.Comment: 11 pages, 7 Figure
Imaging internal flows in a drying sessile polymer dispersion drop using Spectral Radar Optical Coherence Tomography (SR-OCT)
In this work, we present the visualization of the internal flows in a drying sessile polymer dispersion drop on hydrophilic and hydrophobic surfaces with Spectral Radar Optical Coherence Tomography (SR-OCT).We have found that surface features such as the initial contact angle and pinning of the contact line, play a crucial role on the flow direction and final shape of the dried drop. Moreover, imaging through selection of vertical slices using optical coherence tomography offers a feasible alternative compared to imaging through selection of narrow horizontal slices using confocal microscopy for turbid, barely transparent fluids
Improved methods for detecting gravitational waves associated with short gamma-ray bursts
In the era of second generation ground-based gravitational wave detectors,
short gamma-ray bursts (GRBs) will be among the most promising astrophysical
events for joint electromagnetic and gravitational wave observation. A targeted
search for gravitational wave compact binary merger signals in coincidence with
short GRBs was developed and used to analyze data from the first generation
LIGO and Virgo instruments. In this paper, we present improvements to this
search that enhance our ability to detect gravitational wave counterparts to
short GRBs. Specifically, we introduce an improved method for estimating the
gravitational wave background to obtain the event significance required to make
detections; implement a method of tiling extended sky regions, as required when
searching for signals associated to poorly localized GRBs from Fermi Gamma-ray
Burst Monitor or the InterPlanetary Network; and incorporate astrophysical
knowledge about the beaming of GRB emission to restrict the search parameter
space. We describe the implementation of these enhancements and demonstrate how
they improve the ability to observe binary merger gravitational wave signals
associated with short GRBs.Comment: 13 pages, 6 figure
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