Probes of strong-field gravity

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2012.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (p. 221-234).In this thesis, I investigate several ways to probe gravity in the strong-field regime. These investigations focus on observables from the gravitational dynamics, i.e. when time derivatives are large: thus I focus on sources of gravitational waves. Extreme mass-ratio inspirals (EMRIs) can be very sensitive probes of strong-field physics. Predicting observables from EMRIs must be done numerically, so accurate numerical methods are required to ensure that any comparison with measurement is not spoiled by numerical artefacts. The first investigation of this thesis is a spectral (in the angular sector), pseudospectral (in the radial sector) time-domain PDE solver for perturbations of a Kerr black hole (i.e. solving the Teukolsky equation). The method exhibits good convergence and prompts much future investigation. A second approach to probing strong gravity is to consider theories which are general relativity (GR) with a few small corrections and investigate the effect of these corrections on observables. Since gravitational waves are the prime observable and they control the long-term evolution of dynamical systems, I investigate their properties in almost-GR theories. The second investigation of this thesis is a study of the propagation and energy content of gravitational waves in these theories. I find that in a large class of theories, approaching the asymptotically at part of spacetime, gravitational waves propagate in the same fashion as in GR and have the same effective stress-energy tensor as in GR. Next, I study the strong-field correction to the structure of a Schwarzschild black hole in a class of theories. Finally, with these ingredients, I investigate the leading corrections to the dynamics and observables of a comparable mass-ratio inspiral using post-Newtonian techniques. The main result is the appearance of dipolar scalar radiation in this class of theories. The dipolar radiation has a frequency dependence which does not arise in GR and is a distinct signature of corrections. Such signatures should be testable using gravitational wave detection and pulsar timing.by Leo Chaim Stein.Ph.D

Observation of a kilogram-scale oscillator near its quantum ground state

We introduce a novel cooling technique capable of approaching the quantum ground state of a kilogram-scale system—an interferometric gravitational wave detector. The detectors of the Laser Interferometer Gravitational-wave Observatory (LIGO) operate within a factor of 10 of the standard quantum limit (SQL), providing a displacement sensitivity of 10[superscript −18] m in a 100 Hz band centered on 150 Hz. With a new feedback strategy, we dynamically shift the resonant frequency of a 2.7 kg pendulum mode to lie within this optimal band, where its effective temperature falls as low as 1.4 μK, and its occupation number reaches about 200 quanta. This work shows how the exquisite sensitivity necessary to detect gravitational waves can be made available to probe the validity of quantum mechanics on an enormous mass scale.Alfred P. Sloan FoundationUnited States. National Aeronautics and Space AdministrationDavid & Lucile Packard FoundationResearch CorporationNational Science Foundation (U.S.

Search for gravitational waves from binary black hole inspiral, merger, and ringdown

We present the first modeled search for gravitational waves using the complete binary black-hole gravitational waveform from inspiral through the merger and ringdown for binaries with negligible component spin. We searched approximately 2 years of LIGO data, taken between November 2005 and September 2007, for systems with component masses of 1–99M⊙ [1-99 M circled dot operator] and total masses of 25–100M⊙ [25-100 M circled dot operator]. We did not detect any plausible gravitational-wave signals but we do place upper limits on the merger rate of binary black holes as a function of the component masses in this range. We constrain the rate of mergers for 19M⊙≤m1 [19 M circled dot operator greater than or equal to m subscript 1], m2≤28M⊙ [m subscript 2 greater than or equal to 28 M circled dot operator] binary black-hole systems with negligible spin to be no more than 2.0  Mpc-3 {Mpc superscript -3] Myr-1 [Myr superscript -1] at 90% confidence.National Science Foundation (U.S.)United States. National Aeronautics and Space AdministrationCarnegie TrustLeverhulme TrustDavid & Lucile Packard FoundationResearch CorporationAlfred P. Sloan Foundatio

Search for gravitational waves associated with the August 2006 timing glitch of the Vela pulsar

The physical mechanisms responsible for pulsar timing glitches are thought to excite quasinormal mode oscillations in their parent neutron star that couple to gravitational-wave emission. In August 2006, a timing glitch was observed in the radio emission of PSR B0833-45, the Vela pulsar. At the time of the glitch, the two colocated Hanford gravitational-wave detectors of the Laser Interferometer Gravitational-wave observatory (LIGO) were operational and taking data as part of the fifth LIGO science run (S5). We present the first direct search for the gravitational-wave emission associated with oscillations of the fundamental quadrupole mode excited by a pulsar timing glitch. No gravitational-wave detection candidate was found. We place Bayesian 90% confidence upper limits of 6.3×10-21 to 1.4×10-20 on the peak intrinsic strain amplitude of gravitational-wave ring-down signals, depending on which spherical harmonic mode is excited. The corresponding range of energy upper limits is 5.0×1044 to 1.3×1045  erg.David & Lucile Packard FoundationUnited States. National Aeronautics and Space AdministrationAlfred P. Sloan FoundationCarnegie TrustNational Science Foundation (U.S.)Research CorporationLeverhulme Trus