11 research outputs found
Quasi-linear static solutions in massive gravity
The static vacuum spherically symmetric solutions of massive gravity theories
possess two integration constant: the mass M and a scalar charge S. The
presence of this scalar charge reflects the modification of the gravitational
interaction as compared to General Relativity. Surprisingly, these solutions
are non-linear even at large distances from the sources, implying that their
asymptotic behavior is different from that obtained in the linear perturbation
theory. The aim of this paper is to understand how these modified spherically
symmetric solutions emerge from a quasi-linear approximation in order to
generalize them to any arbitrary mass distribution. Along with these modified
solutions, we found a new class of static solutions having a Yukawa shape
Theoretical and phenomenological aspects of theories with massive gravitons
In this thesis, we study three aspects of theories with massive gravitational
waves. In the first part, we review to problems and issues of theories with
massive gravitons before introducing models where Lorentz invariance is
spontaneously broken by the vacuum expectation value of four scalar fields. In
the second part, we discuss three aspects of these models: instantaneous
interaction, spherically vacuum solutions and cosmological perturbations.Comment: PhD thesis, 116 page
Instantaneous interaction in massive gravity
In general relativity, the instantaneous contributions to the gravitational
potentials cancel each other in observable, leaving the theory free of physical
instantaneous interactions. In models where these subtle cancellations are
spoiled by the presence of fields that break Lorentz invariance, physical
instantaneous interactions are possible. Such interactions are studied for a
model of Lorentz- violating massive gravity
Black hole solutions in massive gravity
The static vacuum spherically symmetric solutions in massive gravity are
obtained both analytically and numerically. The solutions depend on two
parameters (integration constants): the mass M (or, equivalently, the
Schwarzschild radius), and an additional parameter, the "scalar charge" S. At
zero value of S and positive mass the standard Schwarzschild black hole
solutions are recovered. Depending on the parameters of the model and the signs
of M and S, the solutions may or may not have horizon. Those with the horizon
describe modified black holes provided they are stable against small
perturbations. In the analytically solvable example, the modified black hole
solutions may have both attractive and repulsive (anti-gravitating) behavior at
large distances. At intermediate distances the gravitational potential of a
modified black hole may mimics the presence of dark matter. Modified black hole
solutions are also found numerically in more realistic massive gravity models
which are attractors of the cosmological evolution.Comment: Original version + erratu
Searching for stochastic gravitational waves using data from the two colocated LIGO Hanford detectors
Searches for a stochastic gravitational-wave background (SGWB) using terrestrial detectors typically involve cross-correlating data from pairs of detectors. The sensitivity of such cross-correlation analyses depends, among other things, on the separation between the two detectors: the smaller the separation, the better the sensitivity. Hence, a colocated detector pair is more sensitive to a gravitational-wave background than a noncolocated detector pair. However, colocated detectors are also expected to suffer from correlated noise from instrumental and environmental effects that could contaminate the measurement of the background. Hence, methods to identify and mitigate the effects of correlated noise are necessary to achieve the potential increase in sensitivity of colocated detectors. Here we report on the first SGWB analysis using the two LIGO Hanford detectors and address the complications arising from correlated environmental noise. We apply correlated noise identification and mitigation techniques to data taken by the two LIGO Hanford detectors, H1 and H2, during LIGO’s fifth science run. At low frequencies, 40–460 Hz, we are unable to sufficiently mitigate the correlated noise to a level where we may confidently measure or bound the stochastic gravitational-wave signal. However, at high frequencies, 460–1000 Hz, these techniques are sufficient to set a 95% confidence level upper limit on the gravitational-wave energy density of Ω(f) < 7.7 × 10[superscript -4](f/900  Hz)[superscript 3], which improves on the previous upper limit by a factor of ~180. In doing so, we demonstrate techniques that will be useful for future searches using advanced detectors, where correlated noise (e.g., from global magnetic fields) may affect even widely separated detectors.National Science Foundation (U.S.)United States. National Aeronautics and Space AdministrationCarnegie TrustDavid & Lucile Packard FoundationAlfred P. Sloan Foundatio
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First Searches for Optical Counterparts to Gravitational-wave Candidate Events
During the LIGO and Virgo joint science runs in 2009-2010, gravitational wave (GW) data from three interferometer detectors were analyzed within minutes to select GW candidate events and infer their apparent sky positions. Target coordinates were transmitted to several telescopes for follow-up observations aimed at the detection of an associated optical transient. Images were obtained for eight such GW candidates. We present the methods used to analyze the image data as well as the transient search results. No optical transient was identified with a convincing association with any of these candidates, and none of the GW triggers showed strong evidence for being astrophysical in nature. We compare the sensitivities of these observations to several model light curves from possible sources of interest, and discuss prospects for future joint GW-optical observations of this type