Dissertations / Theses on the topic 'Gravitational wave'
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Takahashi, Ryuichi. "Wave Effects in the Gravitational Lensing of Gravitational Waves from Chirping Binaries." 京都大学 (Kyoto University), 2004. http://hdl.handle.net/2433/147805.
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Herrera, Martín Antonio. "Wave dark matter as a gravitational lens for electromagnetic and gravitational waves." Thesis, University of Glasgow, 2018. http://theses.gla.ac.uk/9027/.
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The majority of the matter in the known universe is believed to be in the form of Dark Matter, and its widely accepted description is done by Cold Dark Matter (CDM). Nevertheless, its exact properties and composition are still unknown, and it is one of the most active areas of research in Cosmology. The use of Cold Dark Matter has been successful to describe the general behaviour of Dark Matter at large scales. However, it has encountered problems explaining phenomena at other regimes as on the scale of galaxy halos. Therefore, other models have been proposed over time which are able to retain the reasonable success of CDM on large scales and extent it to other regimes where CDM has problems to explain the observed data. One of such models is Scalar field Dark Matter (SFDM). Its properties allow it to produce similar results at large scales and solve the problems encountered at galactic scales. Nevertheless, the difficulty to obtain direct observations of Dark Matter makes it difficult to give a definitive comparison between the models. Therefore, it is important to study dark matter through different methods of analysis that would allow to increase the validity of its scope, and these methods are constantly being researched. In this work, a particular density profile known as Wave Dark Matter is implemented as a gravitational lens to study its behaviour in the cases where it produces strong lensing of light and of gravitational waves. Analytical functions for the description of a soliton core and a soliton core + NFW tail are applied to a sub-sample of 6 galaxies from The Sloan Lens ACS Survey to constrain the lensing parameters and their relation with the profile. Furthermore, by considering the soliton core to be the main contributor to the mass profile, this is implemented as a lens for the case of the wave approximation and further to describe the major effects of the lens on gravitational waves. It was found that the soliton core is too compact and dense in order to reproduce the observed values of the data for the lensed galaxies. However, adding a NFW tail alleviates the problem and reaches radii and masses within the range reported in the literature, although the size of the NFW tail cannot be properly constrained. Meanwhile for gravitational waves, it was found that the lensing parameters of the soliton core, if they are expected to describe a galaxy, will be such that they are more likely to be observed spaceborne gravitational wave detectors. In summary, therefore, a wave dark matter soliton in combination with a NFW tail is able to represent a galaxy, and the combination of ligh and gravitational waves should give new insight on the validity of the profile as a description of Dark Matter galactic haloes.
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Talukder, Dipongkar. "Multi-baseline gravitational wave radiometry." Pullman, Wash. : Washington State University, 2008. http://www.dissertations.wsu.edu/Thesis/Fall2008/d_talukder_112408.pdf.
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Thesis (M.S. in physics)--Washington State University, December 2008.Title from PDF title page (viewed on June 19, 2009). "Department of Physics and Astronomy." Includes bibliographical references (p. 44-46).
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O'Shaughnessy, Richard William Thorne Kip S. "Topics in gravitational wave astronomy /." Diss., Pasadena, Calif. : California Institute of Technology, 2004. http://resolver.caltech.edu/CaltechETD:etd-08052003-161044.
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Lovelace, Geoffrey Mark Thorne Kip S. Thorne Kip S. "Topics in gravitational-wave physics /." Diss., Pasadena, Calif. : California Institute of Technology, 2007. http://resolver.caltech.edu/CaltechETD:etd-05232007-115433.
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Shaddock, Daniel Anthony, and Daniel Shaddock@jpl nasa gov. "Advanced Interferometry for Gravitational Wave Detection." The Australian National University. Faculty of Science, 2001. http://thesis.anu.edu.au./public/adt-ANU20020227.171850.
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In this thesis we investigate advanced techniques for the readout and control of various interferometers. In particular, we present experimental investigations of interferometer configurations and control techniques to be used in second generation interferometric gravitational wave detectors. We also present a new technique, tilt locking, for the readout and control of optical interferometers.
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We report the first experimental demonstration of a Sagnac interferometer with resonant sideband extraction (RSE). We measure the frequency response to modulation of the length of the arms and demonstrate an increase in signal bandwidth of by a factor of 6.5 compared to the Sagnac with arm cavities only. We compare Sagnac interferometers based on optical cavities with cavity-based Michelson interferometers and find that the Sagnac configuration has little overall advantage in a cavity-based system.
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A system for the control and signal extraction of a power recycled Michelson interferometer with RSE is presented. This control system employs a frontal modulation scheme requiring a phase modulated carrier field and a phase modulated subcarrier field. The system is capable of locking all 5 length degrees of freedom and allows the signal cavity to be detuned over the entire range of possibilities, in principle, whilst maintaining lock. We analytically investigate the modulation/demodulation techniques used to obtain these error signals, presenting an introductory explanation of single sideband modulation/demodulation and double demodulation.
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This control system is implemented on a benchtop prototype interferometer. We discuss technical problems associated with production of the input beam modulation components and present several solutions. Operation of the interferometer is demonstrated for a wide range of detunings. The frequency response of the interferometer is measured for various detuned points and we observe good agreement with theoretical predictions. The ability of the control system to maintain lock as the interferometer is detuned is experimentally demonstrated.
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Tilt locking, a new technique to obtain an error signal to lock a laser to an optical cavity, is presented. This technique produces an error signal by efficient measurement of the interference between the TEM00 and TEM10 modes. We perform experimental and theoretical comparisons with the widely used Pound-Drever-Hall (PDH) technique. We derive the quantum noise limit to the sensitivity of a measurement of the beam position, and using this result calculate the shot noise limited sensitivity of tilt locking. We show that tilt locking has a quantum efficiency of 80%, compared to 82% for the PDH technique.
We present experimental demonstrations of tilt locking in several applications including frequency stabilisation, continuous-wave second harmonic generation, and injection locking of a Nd:YAG slab laser. In each of these cases, we demonstrate that the performance of tilt locking is not the limiting factor of the lock stability, and show that it achieves similar performance to the PDH based system.
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Finally, we discuss how tilt locking can be effectively applied to two beam interferometers. We show experimentally how a two beam interferometer typically gives excellent isolation against errors arising from changes in the photodetector position, and experimentally demonstrate the use of tilt locking as a signal readout system for a Sagnac interferometer.
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Dickson, Christopher. "Coincidence analysis of gravitational wave data." Thesis, Cardiff University, 1993. http://orca.cf.ac.uk/6809/.
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Tinto, M. "Theoretical aspects of gravitational wave detection." Thesis, Bucks New University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380273.
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Rubbo, Louis Joseph. "Gravitational wave astronomy using spaceborne detectors." Diss., Montana State University, 2004. http://etd.lib.montana.edu/etd/2004/rubbo/RubboL0805.pdf.
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Fredriksson, Felicia. "Investigating residuals from gravitational wave events GW151012 and GW151226." Thesis, Uppsala universitet, Teoretisk fysik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-389464.
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Fischer, P., D. Grumiller, W. Kummer, D. V. Vassilevich, and Andreas Cap@esi ac at. "S--Matrix for s--Wave Gravitational Scattering." ESI preprints, 2001. ftp://ftp.esi.ac.at/pub/Preprints/esi1029.ps.
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Janson, Oskar. "Gravitational Wave Interaction in a Vlasov Plasma." Thesis, Umeå universitet, Institutionen för fysik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-72776.
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Gravitational waves are predicted by Einstein’s general theory of relativity and have so far only been indirectly detected. The first direct detection should however only be a matter of time, with observatories across the world working hard to detect them. Once gravitational waves are detected they are predicted to be very useful in the field of astronomy. In order to be able to successfully interpret measurements from gravitational waves we need to have knowledge of how the wave is affected by its medium of propagation. Because of that, the purpose of this thesis is to investigate the behaviour of gravitational waves in the medium of a magnetised plasma. Using a kinetic plasma model, Einstein’s field equations and tetrad formalism, a general solution for a gravitational wave propagating in the medium is derived. The general solution is then used to find the dispersion relation of the gravitational wave for two special cases: the case of Alfvén resonance and the case of cyclotron resonance. The Alfvén case is already studied in the literature and is found to match the previous results saying it will not affect the wave much. The cyclotron resonance case is new and was chosen it can magnify the effects of the particles on the gravitational wave. The cases are studied with regards to detectability of a medium induced dispersion. The influence on the gravitational wave propagation is, however, found to be too small for dispersive effects to be detected in the cases studiedGravitationsvågor förutses i Einsteins allmänna relativitetsteori och har så här långt endast blivit indirekt detekterade. Den första direkta detektionen är dock bara en tidsfråga och observatorier runtom i världen arbetar hårt för att lyckas med den. Då gravitationsvågor väl är detekterade sägs de ha stor potential inom astronomi. För att man ska kunna tolka mätdata från gravitationsvågor behöver man veta hur vågen beter sig i propagationsmediet. Av den anledningen är syftet med detta examensarbete att undersöka hur gravitationsvågor beter sig i ett magnetiserat plasma. Med hjälp av en modell för kinetisk plasma, Einsteins fältekvationer och tetradformalism härleds en allmän lösning för en gravitationsvåg som propagerar i en magnetiserad plasma fram. Lösningen används därefter för att hitta dispersionsrelationen för gravitationsvågen givet två specialfall: fallet för Alfvénresonans och fallet för cyklotronresonens. Alfvénfallet är redan studerat i tidigare litteratur och resultatet man hittar visar sig stämma överens med det tidigare funna resultatet som säger att det inte har en märkbar påverkan på vågen. Cyklotronresonansfallet är nytt och valdes eftersom att det kan förstärka de effekter som partiklarna har på gravitationsvågen. De båda specialfallen studeras närmare med avseende på detektion av en dispersion inducerad av mediet. Påverkan på gravitationsvågens propagation sluts dock till att vara för liten för att den ska bli uppmätt i de undersökta fallen.
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Taylor, John R. "Interferometric experiments towards advanced gravitational wave detectors." Thesis, University of Glasgow, 2009. http://theses.gla.ac.uk/727/.
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In 1905, Einstein postulated that the speed of light is not only finite, but that its speed in vacuum is a universal limit that no process can exceed. The Theory of General Relativity later extended this concept to include gravitational interactions, and Eddington's timely measurements of stellar positions during a solar eclipse in 1919 confirmed that gravity's effect on spacetime is both real and entirely physical -- not merely a mathematical curiosity. With the death of Newton's notions of universal time and instantaneous gravity came the idea of gravitational waves as distortions in space-time that propagate the gravitational interaction at the speed of light. These gravitational waves are emitted from any object undergoing a non-axi-symmetric acceleration of mass, but -- due to the exceptionally weak coupling between gravitational waves and matter -- are expected to induce displacements of the order of 10^-18 m in kilometre-scale detectors: the extraordinary diminutiveness of this effect has thus far precluded any direct detection of the phenomenon. Numerous gravitational wave detectors have been built since the 1960s, in the form of both interferometric detectors and resonant mass devices. Interferometric detectors currently represent the most promising form of detector, due to their relatively wide-band response to gravitational wave signals and promising levels of sensitivity. In recent years a worldwide network of these interferometric detectors (LIGO, GEO600, Virgo and TAMA300) have begun to approach (or indeed reach) their design sensitivities. Although these detectors have started to provide upper limit results for gravitational wave emission that are of astrophysical significance, there have as yet been no direct detections. As such, work is underway to upgrade and improve these detectors. However, increasing the signal sensitivity necessarily leads to an increase in their sensitivity to their limiting noise sources. Two critical noise limits that must be characterised, understood, and hopefully reduced for the benefit of future detectors, are thermal noise (from mirror substrates, reflective coatings and suspension systems) and photon noise -- associated with the intrinsic shot noise of light and the noise due to light's radiation pressure. Two interferometric experiments designed to help inform on these phenomena were constructed at the University of Glasgow's Institute for Gravitational Research. The first experiment compared the relative displacement noise spectra of two specially constructed optical cavities, to extract the thermal noise spectrum of a single test mirror. In future experiments, this optic could be changed and the thermal noise spectrum for any suitable combination of mirror substrate and reflective coating evaluated. The second experiment involved the investigation of suitable control schemes for a three-mirror coupled optical cavity. As the resonant light power in interferometers increases in future devices (in order to decrease the photon shot noise) the need to de-couple the control schemes that govern the respective cavities so that they can be controlled independently, becomes more important. As a three-mirror cavity effectively represents a simple coupled system, it provides a suitable test-bed for characterising suitable control schemes for more advanced interferometers. Together, these experiments may provide information useful to the design of future gravitational wave interferometers.
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Tang, Chein-Jen. "Detecting Cosmic Gravitational-wave Background with LISA." Thesis, Imperial College London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.508491.
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Lawrence, Sean P. A. "Analysis of fluid and gravitational wave oscillations." Thesis, Cardiff University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316341.
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Killow, Christian J. "Interferometry developments for spaceborne gravitational wave detectors." Thesis, University of Glasgow, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.426535.
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Mingarelli, Chiara Maria Francesca. "Gravitational wave astrophysics with pulsar timing arrays." Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/5117/.
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This thesis focuses on gravitational wave (GW) astrophysics with Pulsar Timing Arrays (PTAs). Firstly it is shown that anisotropy in the GW background may be present, and that its characterization at different angular scales carries important information. The standard analysis for isotropic backgrounds is then generalized by decomposing the angular distribution of the GW energy density into multipole moments. Generalized overlap reduction functions (ORFs) are computed for a generic level of anisotropy and PTA configuration. A rigorous analysis is then done of the assumptions made when calculating ORFs. It is shown that correlated phase changes introduce previously unmodeled effects for pulsars pairs separated by less than a radiation wavelength. The research then turns to the study of continuous GW sources from supermassive black hole binaries (SMBHBs). Here it shown that the detection of GWs from SMBHB systems can yield direct information about the masses and spins of the black holes, provided that the GW-induced timing fluctuations both at the pulsar and at Earth are detected. This in turn provides a map of the nonlinear dynamics of the gravitational field and a new avenue to tackle open problems in astrophysics connected to the formation and evolution of SMBHs.
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Lee, Kyung Ha. "Suspension upgrades for future gravitational wave detectors." Thesis, University of Glasgow, 2019. http://theses.gla.ac.uk/40954/.
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To further increase the sensitivity of the aLIGO detectors, upgrading the monolithic fused silica suspension is considered for an upgrade option: a higher stress in the fibre and a longer final stage. One of the challenges for this upgrade will be producing thinner and longer fibres that can hold the test mass safely. Since laser power fluctuations during the fibre fabrication process can produce potentially weak fibres, we present a laser intensity stabilisation technology for fused silica fibre fabrication that was investigated to allow further improvements on fibre production consistency which could be applied to aLIGO upgrades. Fibres fabricated with this new technique showed 30% decreased standard deviation of breaking stress, which indicates that the application of intensity stabilisation technology can improve the statistical strength of fused silica fibres. Combined with a longer polishing duration, the average breaking stress also improved by 9%. As higher stress in the fibre and the longer final stage can improve the detector's sensitivity, these enhanced technologies will enable us to fabricate thin and robust fibres that can achieve future suspension upgrade requirements.
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Fritschel, Peter Kurt. "Techniques for laser interferometer gravitational wave detectors." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/77753.
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Oelker, Eric Glenn. "Squeezed states for advanced gravitational wave detectors." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/107044.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 219-229).
Quantum vacuum fluctuations impose strict limits on precision displacement measurements, those of interferometric gravitational-wave detectors among them. Introducing squeezed states into an interferometer's readout port can improve the sensitivity of the instrument, leading to richer astrophysical observations. In recent years, this technique has been used to improve the sensitivity of the GEO600 [1011 and the Initial LIGO detector at Hanford, WA [102]. Squeezed states could be employed in advanced gravitational-wave detectors, such as Advanced LIGO, to further push the limits of the observable gravitational wave universe. To maximize the benefit from squeezing, environmentally induced disturbances such as back scattering and angular jitter need to be mitigated. Also, optomechanical interactions dictate that the quadrature of the squeezed vacuum state must rotate by 900 at around 50 Hz in order to achieve a broadband sensitivity improvement for Advanced LIGO. In this thesis we describe a series of experiments that lead to a ultra-high vacuum (UHV) compatible, low phase noise, and frequency-dependent squeezed vacuum source required for Advanced LIGO and future gravitational-wave detectors. In order to develop the required technology, two proof-of-principal experiments were conducted. In the first experiment, we built a UHV compatible squeezed vacuum source and homodyne readout and operated them in UHV conditions. We also commissioned a control scheme that achieved a record low 1.30-7 mrad of phase noise. This is a nearly tenfold improvement over previously reported measurements with audio-band squeezed vacuum sources. In the second experiment we used a 2-m-long, high-finesse optical resonator to produce frequency-dependent squeezed quadrature rotation around 1.2kHz. This demonstration of audio-band frequency-dependent squeezing uses technology and methods that are scalable to the required rotation frequency for Advance LIGO, firmly establishing the viability of this technique for application in current and future gravitational-wave detectors. We conclude with a discussion of the implications of these results for squeezing enhancement in Advanced LIGO and beyond.
by Eric Oelker.
Ph. D.
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Guilbert, Marc. "Gravitational wave signatures of cosmic string bursts." Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.614810.
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Nuttall, L. K. "Electromagnetic follow-up of gravitational wave candidates." Thesis, Cardiff University, 2013. http://orca.cf.ac.uk/47562/.
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Observations of astrophysical systems in different wavelengths can reveal insights in to systems which are not available from a single wavelength. The same can be expected from multi-channel observations of systems which also produce gravitational waves (GWs). The most likely source of strong, detectable GWs, which will also produce an electromagnetic (EM) signature, is the merger of compact objects containing neutron stars (NS) and black holes (BH), namely NS-NS and NS-BH systems. The focus of this thesis is to summarise current and past efforts to detect an EM counterpart of a GW event, with emphasis on compact merger sources. To begin, the formulation of GWs in general relativity is brie y discussed, as well as the main classes of GW sources. The global networks of GW interferometers in the recent past and near future are described, together with brief explanations of operational principles and the main challenges GW detectors face to make a confident detection. Current literature is reviewed to give a brief summary of the most promising sources which produce both GW and EM signals. Emphasis is given to gamma-ray bursts (GRBs), their afterglows, and kilonovae. In addition a brief description of GW searches triggered by an external source (such as a GRB) is given. A new form of search is then discussed in which GW events are used to point conventional EM telescopes, with emphasis on rapidly slewing, wide field of view optical telescopes. The main challenge in this form of search is that timing information from a network of GW interferometers yields large error regions for the source sky direction making it diffcult to locate an EM transient. Therefore a new statistic is presented in which galaxies (taken from a galaxy catalogue) within this search region are ranked. The probability of identifying the host galaxy of a GW signal from NS-NS and NS-BH systems is investigated and results presented for past and future GW detector configurations. The ROTSE-III telescope system took part in this first search for EM counterparts of GW triggers. With four identical robotic telescopes located across the world it responded to five GW events. Presented is an automation of the ROTSE image processing pipeline which allows large-scale processing and automated validation and classification of candidates. A background study was conducted to better understand the optical transient background and to determine the statistical significance of candidates. Pipeline performance is tested by inserting simulated transients following kilonova and GRB lightcurves in to images; an efficiency study is described. Finally the results of the images taken in response to the five GW events are presented and discussed.
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Hu, Yiming. "Novel inference methods for gravitational wave astrophysics." Thesis, University of Glasgow, 2015. http://theses.gla.ac.uk/6441/.
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With the development of more and more elegant and sensitive interferometric gravitational wave detectors, we are expecting the first direct detection of gravitational waves in a short time. This triggers huge interest to develop more powerful tools to perform data analysis on these signals, and to develop a good understanding of the analysis so that confident conclu- sions can be made. A further step would be to view into the future, as the first detections will boost the scientific demands for more powerful future generation detectors, which identifies the task of optimising the site of such detectors. Bayesian Inference plays a vital role in data analysis, and one excellent example that demon- strates its usefulness is its ability to resolve the tension between multiple models using the methodology of Bayesian Model Selection. In this thesis we apply this methodology to the timing data of pulses from the pulsar 1E 2259+586. With a set of different choices for the prior range, a fair and quantitative comparison can be made between two competing models: that of so-called successive anti-glitches and an anti-/normal glitch pair. Our analysis of the data shows a consistent support for the successive anti-glitches model, with a Bayes Factor of ∼ 45, where the uncertainty has been estimated from nested sampling and from multiple runs that are slightly different, but still within a factor of two, showing a general consistency. Simplifying the timing model will only make the Bayes Factor even bigger, while the two event model is overwhelmingly supported over the one event model. In gravitational wave data analysis, posteriors are generally complicated structures contain- ing multiple modes. A novel algorithm to achieve efficient sampling for multi-modal pos- teriors, known as mixed MCMC, is proposed in this thesis. This enables communication between multiple regions within the parameter space by adopting a novel jump proposal. We present the mixed MCMC algorithm and first apply it to a toy model problem, where the likelihood may be determined theoretically. By comparing the theoretical and empiri- cally sampled values of 2 log(L) for credible regions that correspond to 68.27%, 95.45% and 99.73%, we conclude that for our illustrative model the sampling result of mixed MCMC is consistent with the theoretical prediction with small uncertainty. Since it does not re- quire multiple chains with different temperatures, mixed MCMC can boost the efficiency of sampling by design, compared with (for example) parallel tempering MCMC. The sampling strategy of mixed MCMC can be helpful for not only Bayesian Inference, but also more general problems like the global optimisation of future generations of Gravita- tional Wave Detectors. As we expect such problem to be intrinsically high dimensional and multi-modal, mixed MCMC is a suitable sampling method, and we develop and apply it in this thesis. Based on our analysis it is concluded that for both a 3-detector-network and a 5-detector-network, Australia hosts the “best” site, in the sense that such site is most flex- ible, i.e. it can be involved in the largest number of detector networks, involving different component sites, that have a high ‘Figure of Merit’. The work of gravitational wave data analysis leads to the ultimate goal of making a direct detection of gravitational waves, which in turn requires the ability of distinguish astronomi- cal signals from a noisy background, and assess the significance of each gravitational wave ‘trigger’ (i.e. candidate event) appropriately. There are two types of method for estimating significance and these differ by the key distinction of either removing the foreground events from the background estimation or keeping them in the analysis. This thesis presents the results of a Mock Data Challenge (MDC), carried out within the LIGO Scientific Collabo- ration using different data analysis pipelines, designed to investigate these two methods for estimating significance. It contains a variety of background complexity ranging from simple, realistic to complex, and foreground event rate ranging from zero, low, medium and high. Analysis of the MDC results illustrated that generally all methods for determining the sig- nificance agree well with each other, irrespective of the background complexity. However, a discrepancy became apparent between the results for removal or non-removal of foreground events, for events below a significance level of < 10−3. Our results demonstrated that the removal method is an unbiased estimator for the mean of the significance. However, as the most scientifically interesting events are likely to have a very small numerical value for their significance, such method would overestimate that significance for most of the realisations.
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McWilliams, Sean Thomas. "Applying numerical relativity to gravitational wave astronomy." College Park, Md. : University of Maryland, 2008. http://hdl.handle.net/1903/8050.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2008.Thesis research directed by: Dept. of Physics. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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White, Darren J. "Electromagnetic follow-up of gravitational wave candidates." Thesis, University of Sheffield, 2014. http://etheses.whiterose.ac.uk/5443/.
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In the near future, gravitational wave (GW) detections are expected to become common, opening a new window on the Universe. Using the two 4 km Laser Interferometer Gravitational wave Observatory (LIGO) detectors and the 3 km Virgo detector we can triangulate a passing GW to a region of the sky with an area of tens of square degrees. These regions can then be observed using electromagnetic (EM) observatories. Pairing GW and EM observations can verify the astrophysical origin of a GW detection, and provide a more complete picture of the processes taking place. This thesis describes the first triggered search for EM counterparts to GW candidates from the 2009-2010 LIGO/Virgo observing run. To improve the search strategy of this observing run, we created a catalogue of galaxies within 100 Mpc, known as the Gravitational Wave Galaxy Catalogue (GWGC), which was used to select locations in the GW skymaps to be imaged by EM partner observatories. Analysis of optical images taken as part of this run, from the Liverpool Telescope (LT) and ROTSE observatory network, find no associated counterparts. We also simulate the optical transients expected from GW sources across the LIGO/Virgo horizon of 50 Mpc, and find that the LT would be able to detect most optical counterparts across the majority of the horizon distance, while ROTSE can only detect counterparts over a fraction of the same distance. Finally, we present the design specifications of GOTO, a wide field-of-view observatory to image the skymaps expected to be produced by the next generation of GW detectors. This telescope will be able to cover ∼70 square degrees to a limiting magnitude of ∼21, the sky area and limiting magnitude required to offer a reasonable chance of detecting an EM counterpart. While NS-NS merger models are uncertain, a tentative first detection of a kilonova-like counterpart to GRB130603B leaves us optimistic that the advanced detector era will provide the first GW detections and EM counterparts.
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Powell, Jade. "Model selection for gravitational-wave transient sources." Thesis, University of Glasgow, 2017. http://theses.gla.ac.uk/8259/.
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A hundred years after Einstein predicted the existence of gravitational waves, the first direct detection was made from gravitational waves emitted by a binary black hole system. Other potential sources for an advanced gravitational-wave detector network include core-collapse supernovae. Due to complicated simulations of the physics involved in core-collapse supernovae, the exact waveform of a core-collapse supernova signal is unknown. A detection of a core-collapse supernova signal is challenging, as noise of non-astrophysical origin contaminates the science data taken by the advanced detectors. Noise transients in the detectors limit the false alarm rate of astrophysical detections, and could potentially mimic a core-collapse supernova signal. They can reduce the duty cycle of the detectors, which is particularly harmful for core-collapse supernovae detections due to their low event rate. Prompt characterization of instrumental and environmental noise transients will be critical for improving the sensitivity of the advanced detectors during observing runs. During the science runs of the initial gravitational-wave detectors, noise transients were manually classified by visually examining the time-frequency scan of each event. Here, we present a Bayesian model selection algorithm designed for the automatic classification of noise transients in advanced gravitational-wave detectors. The algorithm is tested on simulated data sets and real non-Gaussian, non-stationary Advanced LIGO noise, and we demonstrate the ability to automatically classify transients by frequency, SNR and waveform morphology. A classification of noise transients as data is taken can lead to an improvement in data quality during an observing run and determine their origin. In this thesis, we show how Bayesian model selection can be used to determine if a core-collapse supernova candidate gravitational-wave signal is a noise transient, a core-collapse supernova signal or other astrophysical transient. If the signal is a core-collapse supernova detection, we show how the core-collapse supernova explosion mechanism can be determined using a combination of principal component analysis and Bayesian model selection. We use the latest three-dimensional simulations of gravitational-wave signals from core-collapse supernovae exploding via neutrino-driven convection and rapidly-rotating core-collapse. We show that with an advanced detector network, we can determine if the core-collapse supernova explosion mechanism is neutrino-driven convection for sources in our Galaxy, and rapidly-rotating core collapse for sources out to the Large Magellanic Cloud.
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Addison, Eric. "Gravitational Wave Astrophysics with Compact Binary Systems." DigitalCommons@USU, 2014. https://digitalcommons.usu.edu/etd/2166.
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In this dissertation, I present two studies in the field of gravitational wave astrophysics applied to compact binary systems. In the first project, I investigate simulated encounters between a binary system comprised of two stellar mass black holes with a galactic supermassive black hole. It is found that binaries disrupted by the supermassive black hole form extreme mass ratio inspirals (EMRIs), which would begin with very high eccentricity, e ≈ 1 − O(10−2), but circularize dramatically by the emission of gravitational wave radiation. At the time when the stable orbit turns over to a plunge orbit, the EMRIs still have some small residual eccentricity, e ≈ 0.05 on average, which is slightly larger than previous estimates. The surviving binaries are classified based on their final relation with the supermassive black hole. When inspecting the merger lifetime of the surviving binaries, a mean new merger lifetime of ˜ T = 0.8T0 is found. Factoring in this new lifetime with other relevant data, I calculate the merger rate of these systems in the range of the advanced Laser Interferometer Gravitational Wave Observatory to be about 0.25 yr−1, which represents a small percentage of the current predicted CBC rates. In the second project I propose and explore a new method of estimating the radius of the accretion disc in cataclysmic variable binary systems though the use of coupled electromagnetic and gravitational wave observations. By identifying the angle of the hot spot formed by the impact of the accretion stream with the disc, φHS, the radius of the disc can be recovered. I test the proposed method against fully simulated lightcurve output, as well as the true observed AM CVn lightcurve. In both cases, I find our method capable of estimating the disc radius to high precision. I calculate a disc radius of ˆRD/a ≈ 0.476°”0.025 for the fully simulated data and ˆRD/a ≈ 0.481 °” 0.05 for the true lightcurve data. These estimates agree with the accepted value of RD = 0.478a within the uncertainties, and differ from the accepted value by 0.4% and 0.6%, respectively. Because this method does not rely on eclipses, it will be applicable to a much broader population of binaries.
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GRIMM, STEFAN JOHANNES. "Parameter Estimation with Future Gravitational Wave Detectors." Doctoral thesis, Gran Sasso Science Institute, 2021. http://hdl.handle.net/20.500.12571/16121.
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The first detection of a gravitational-wave signal of a coalescence of two black holes marked the beginning of the era of gravitational-wave astronomy, which opens exciting new possibilities in the fields of astronomy, astrophysics and cosmology. Driven forward by the wealth of new information provided by detections of the currently operating detectors, the field of gravitational wave science is developing quickly - next-generation detectors that will lift our understanding to a new level are already being planned. In this thesis, I investigate the possibilities for parameter estimation using the Fisher-matrix formalism with combined information from present and future detectors in different frequency bands. The scientific questions I set out to answer are:
• How many sources can these future detectors detect, and how well can an individual detector reconstruct the source parameters?
• How does parameter estimation benefit from combining information from several detectors, in particular from detectors in different frequency bands (multiband approach)?
• How do different choices for the detector (detector geometries for ground-based detectors, orbits for space-borne detectors) influence science goals?
The detectors considered are the LIGO/Virgo detectors, the Einstein Telescope (ET), Cosmic Explorer (CE), the Laser Interferometer Space Antenna (LISA), and the first stage of the Deci-Hertz Interferometer Gravitational wave Observatory (B-DECIGO). The simulation results show that future detectors will detect many more sources (ET), and also new classes of sources (e.g. intermediate-mass binary black holes in ET, B-DECIGO and LISA). However, it became clear that LISA is unlikely to detect any stellar-mass black hole binaries that would merge within a few years, as required for multiband observations. With respect to the parameter estimation capabilities of the detectors, it became clear that future detectors will provide parameter estimates orders of magnitude better than the estimates of the currently operating detectors. Long observation times and the movement of the detectors during the observation time help to break parameter degeneracies and to improve the estimates of the sky localization angles in particular. ET, for example, will be able to determine the sky localization of neutron star binaries, due to the long observation time of these binaries in ET. With regard to multiband observations, the finding is that the mass parameters in particular benefit from combining information from ground-based and space-borne detectors.
The Einstein Telescope is currently envisioned in a triangular configuration consisting of 6 interferometers in total, which, at least in thought experiments, gives flexibility to how these instruments are best combined. I investigate the impact of different configuration scenarios on detection rate and on compact-binary parameter-estimation errors, in particular on sky localization estimates. The scenarios considered are triangular versus L-shape, two sites versus single site, and separation of the low- and high-frequency interferometers forming the xylophone detector of the baseline configuration of the Einstein Telescope. It emerged that the triangular design, while being more complex, offers significant advantages for parameter estimation - it allows for the determination of the sky localization for a few select binaries, and of the inclination angle. I also find that the largest contribution to the Signal-to-noise ratio comes from ET’s low frequency sensitivity - the vast majority of detections can be made with the low-frequency interferometers alone.
For multimessenger observations, binary neutron stars are the most interesting sources. With a state-of-the-art astrophysical model, I studied detection rates of binary neutron stars in triangular ET, and how well it can reconstruct the sky localization, also as a network with the currently operating 2G detectors and CE. I found that ET will detect a vast number of sources, and it will be able to determine their sky position, in particular when working as a network with the 2G detectors and CE. These capabilities are extremely promising for finding answers to many important questions in astrophysics and cosmology.
In conclusion, the results presented in this thesis draw a comprehensive picture of the potential scientific gains of future ground-based and space-borne detectors, and it sheds light on the ramifications of design choices like the choice of detector geometries and orbits.
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Yang, Sheng. "Searching electromagnetic counterparts of gravitational wave signals." Doctoral thesis, Università degli studi di Padova, 2018. http://hdl.handle.net/11577/3427182.
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Gravitational-wave (GW) were detected on 14 September 2015 by the Laser Interferometer Gravitational-wave Observatory (LIGO). The following challenge was the joint observation of a Compact binary coalescence (CBC) in both GW and Electromagnetic (EM) channels. This is difficult because GW sky location uncertainties are typically tens or hundreds of square degrees. Multimessenger observations of binary system containing a neutron star were expected to answer many open questions of modern astrophysics, from the nature of short GRB to the origin of heavy elements. For this reason the astronomical community worldwide was preparing for this event. The work of this thesis was developed in this context. My work focused on the search of the possible optical counterparts of GW events. For the search of the expected optical transient I tested, implemented and exploited two complementary approaches using the data of the observing facilities available to the collaborations of which I am member:
a) The GRAvitational Wave Inaf TeAm (GRAWITA), which performs an optical transient search with the 2.6 meter VLT survey telescope (VST). As part of GRAWITA, I developed the transient detection pipeline based on image difference of the wide field survey. I applied this tool to the follow up of three GW triggers, GW150914, GW151226 and GW170814.
b) The Distance Less Than 40 Mpc survey (DLT40), which makes use of 40 cm robotic telescopes for targeting individual galaxies. In this project, I developed a prioritization algorithm to select galaxies inside the GW error-box, with the aim to maximise the detection probability in case of nearby triggers. My algorithm was used to define the strategy and follow-up ten GW triggers. After a few inconclusive attempts, on August 17, 2017 with DLT40, I contributed to the discovery of the first optical counterpart of a GW source, DLT17ck (labelled also AT2017gfo and SSS17a). With GRAWITA we observed this source with an almost daily cadence for two weeks both in imaging and spectroscopy, proving that the binary neutron star (BNS) merging produces r-process elements. I used the previous record of the DLT40 SN search to derive one of the first direct estimate of the BNS rates. I also contributed to a first attempt to measure the Hubble constant from combined GW-EM observations.
Finally, I developed a machine learning algorithm with the aim of a more rapid and efficient transient candidate selection. This tool is already implemented in the ongoing DLT40 SN survey and it will be used by GRAWITA in the incoming LIGO-VIRGO collaboration (LVC) O3 run.
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Fang, Hua Thorne Kip S. Thorne Kip S. "Topics in gravitational physics : tidal coupling in gravitational wave searches and Mach's principle /." Diss., Pasadena, Calif. : California Institute of Technology, 2007. http://resolver.caltech.edu/CaltechETD:etd-05212007-004257.
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Valentini, Michele. "The longitudinal control for the Advanced Virgo Plus gravitational wave detector." Doctoral thesis, Università degli studi di Trento, 2023. https://hdl.handle.net/11572/363585.
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Ground-based gravitational wave detectors are evolving at a rapid pace. In the five minutes that followed the first direct detection of gravitational waves, the Advanced LIGO and Advanced Virgo experiments have been subject to substantial upgrades, increasing their sensitivities by many times and allowing them to detect dozens of other gravitational wave signals. Third-generation ground-based interferometers (Einstein Telescope and Cosmic Explorer) and spaaace-based detectors (such as LISA) are being researched and planned to enter into function in the second half of the next decade. If successful, these experiments will allow the detection of thousands of signals coming from an ever-increasing range of cosmological sources. In the meantime, second-generation interferometers are approaching the conclusion of ambitious upgrades started with the end of the third observing run “O3” in march 2020. The work of this thesis revolves around the planning and the commissioning of the “Advanced Virgo plus” upgrade project, which aims to increase the detector’s sensitivity by a factor of two, allowing a ten times higher detection rate than the previous configuration. In particular, the main topic is the update of the interferometer longitudinal sensing and control scheme required by the upgrade in the detector’s optical configuration. The design and simulation of the new control scheme catried out in
constant collaboration with the “Interferometer Sensing and Control” team, started minutes before the actual implementation of the upgrades. Following that, I participated in the full-time commissioning of the upgraded configuration, which started in January 2021 and is currently ongoing. We will first explain the new interferometer configuration, then go into the details of the lock-acquisition procedure, presenting the results of the related simulation studies and the commissioning. A particular focus will also be given to the simulations of the interferometer’s state at the end of the lock acquisition, called “steady-state”. In addition to the study and implementation of the current lock-acquisition procedure, the thesis will present simulation activities to study an alternative lock-acquisition technique that has not yet been implemented.
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Servin, Martin. "Nonlinear interaction and propagation of gravitational and electromagnetic waves in plasmas." Doctoral thesis, Umeå University, Physics, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-122.
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Gravitational waves and electromagnetic waves are important as carriers of energy and information. This thesis is devoted to the study of the propagation and interaction of these waves in plasmas, with emphasis on nonlinear effects and applications within astrophysics.
The physical systems are described by the Einstein-Maxwell-fluid equations or Einstein-Maxwell-Vlasov equations, when a kinetic treatment is required. The small amplitude and high-frequency approximation is employed for the gravitational waves, such that perturbative techniques can be applied and space-time can be considered locally flat, with a gravitational radiation field superimposed on it. The gravitational waves give rise to coupling terms that have the structure of effective currents in the Maxwell equations and an effective gravitational force in the equation of motion for the plasma. The Einstein field equations describe the evolution of the gravitational waves, with the perturbed energy-momentum density of the plasma and the electromagnetic field as a source.
The processes that are investigated are gravitational waves exciting electromagnetic waves in plasmas, altering the optical properties of plasmas and accelerating charged particles. The thesis also deals with the propagation propertities of gravitational and electromagnetic waves, e.g. effects due to resonant wave-particle interactions, plasma inhomogeneties and nonlinear self-interactions. It is also shown that plasmas that are not in thermodynamical equilibrium may release their free energy by emitting gravitational waves.
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Casanueva, Diaz Julia. "Control of the gravitational wave interferometric detector Advanced Virgo." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS209/document.
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La première détection d'une Onde Gravitationnelle (OG) a été faite le 14 Septembre 2015 par la collaboration LIGO-Virgo avec les deux détecteurs de LIGO. Elle a été émise par la fusion de deux Trous Noirs, fournissant ainsi la première preuve directe de l’existence des Trous Noirs. Advanced Virgo est la version améliorée de l’interféromètre Virgo et il va rejoindre les détecteurs LIGO dans les mois qui suivent. Le passage d'une OG induit un changement différentiel de la distance entre masses-test (uniquement sensibles à la force gravitationnelle). Cette variation de distance est proportionnelle à l'amplitude de l'OG, néanmoins le déplacement le plus grand qui peut être observé depuis la Terre est de l'ordre de 10⁻¹⁹ m/sqrt(Hz) en terme de densité spectrale. C'est pour cela que l’interféromètre de Michelson est l'instrument idéal pour détecter cet effet différentiel. Les détecteurs d’OG utilisent des miroirs suspendus, qui se comportent comme masses-test. Le passage d'une OG va produire un changement dans la distance entre les miroirs qui va modifier la condition d’interférence et donc une variation de puissance lumineuse mesurée par la photodiode de détection. Cependant, un Michelson simple n'est pas assez sensible et des améliorations ont été ajoutées. La première génération de détecteurs a ajouté des cavités Fabry-Pérot dans les bras pour augmenter le chemin optique. De plus un nouveau miroir a été ajouté pour recirculer la lumière réfléchie vers le laser et augmenter la puissance effective, en créant une nouvelle cavité connue comme Power Recycling Cavity (PRC). Son effet est d’autant plus important que le Michelson est en fait optimalement réglé sur une frange noire. Tous les miroirs du détecteur ressentent le bruit sismique et les longueurs des cavités, entre autres, changent en permanence. Il est donc nécessaire de contrôler activement la position longitudinale et angulaire des cavités pour les maintenir en résonance. Pendant ma thèse j'ai étudié le contrôle de Advanced Virgo d’abord en simulation puis pendant le commissioning lui-même. D'abord j'ai simulé la stratégie de contrôle utilisée dans Virgo avec des simulations modales. L'objectif était de vérifier si la même stratégie pouvait être appliquée à Advanced Virgo ou s'il fallait l'adapter. Avec Advanced Virgo les cavités Fabry-Pérot ont une finesse plus grande ce qui entraîne de nouveaux effets dynamiques et qui demande une stratégie de contrôle spéciale, stratégie que j'ai modifiée pour l'adapter aux besoins du commissioning. Concernant la PRC, j’ai étudié l'impact de sa stabilité dans le fonctionnement de l’interféromètre. Comme elle est très proche de la région d’instabilité, l’onde lumineuse être très sensible à l'alignement et a l'adaptation du faisceau à la cavité. J’ai vérifié avec les simulations son impact sur les contrôles longitudinaux, qui peuvent devenir instables, et une solution a été validée. Ensuite j'ai utilisé cette information pour le commissioning d'Advanced Virgo. Dans cette thèse les détails du commissioning des contrôles longitudinal et angulaire de l’interféromètre sont présentés. La stabilisation en fréquence est aussi présentée, puisqu'elle joue un rôle très important dans le contrôle de l’interféromètre car étant le bruit dominantThe first detection of a Gravitational Wave (GW) was done on September 14 th of 2015 by the LIGO-Virgo collaboration with the two LIGO detectors. It was emitted by the merger of a Binary Black Hole, providing the first direct proof of the existence of Black Holes. Advanced Virgo is the upgraded version of the Virgo interferometer and it will join the LIGO detectors in the next months. The passage of a GW on Earth induces a change on the distance between test masses (experiencing only the gravitational interaction) in a differential way. This distance variation is proportional to the amplitude of the GW however the largest displacement observable on Earth will be of the order of 10⁻¹⁹ m/sqrt(Hz). Taking this in account, a Michelson interferometer is the ideal instrument to detect this differential effect. GWs detectors will use suspended mirrors to behave as test masses. The passage of a GW will cause a change on the distance between the mirrors that will spoil the interference condition, allowing some light to leak to the detection photodiode. However, a simple Michelson interferometer does not provide enough sensitivity. For this reason the first generation of detectors added Fabry-Perot cavities in the arms, in order to increase the optical path. A second change was the addition of an extra mirror in order to recycle the light that comes back towards the laser, to increase the effective power, creating a new cavity also known as Power Recycling Cavity (PRC). Its effect is more important when the Michelson is tuned in an optimal way in a dark fringe. All the mirrors of the detector are affected by the seismic noise and so their distance is continuously changing. It is necessary to control the longitudinal and angular position of the cavities in order to keep them at resonance. During my thesis I have studied the control of Advanced Virgo using simulation and during the commissioning itself. First of all I have simulated the control strategy used in Virgo using modal simulations. The aim was to check if the same strategy could be applied to Advanced Virgo or if it needs adaptation. In Advanced Virgo the Fabry-Perot cavities have a higher finesse, which arises new dynamical problems and requires a special control strategy that I have modified to match the commissioning needs. Regarding the PRC, we have studied the impact of its stability on the performance of the interferometer. As it is very close from the instability region, the electrical field inside will be very sensitive to alignment and matching of the laser beam. We have checked using simulations its impact on the longitudinal controls, which can become unstable, and a solution has been validated. Then I have used this information during the commissioning of the Advanced Virgo detector. In this thesis the details of the commissioning of the longitudinal and angular control of the interferometer will be presented. It includes the frequency stabilization, which has a key role in the control of the interferometer, since it is the dominant noise
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Crowder, Jefferson Osborn. "Data analysis for space-based gravitational wave detectors." Diss., Montana State University, 2006. http://etd.lib.montana.edu/etd/2006/crowder/CrowderJ0506.pdf.
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Littenberg, Tyson Bailey. "A comprehensive Bayesian approach to gravitational wave astronomy." Thesis, Montana State University, 2009. http://etd.lib.montana.edu/etd/2009/littenberg/LittenbergT0509.pdf.
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The challenge of determining whether data from a gravitational wave detector contains signals which are cosmic in origin is the central problem in gravitational wave astronomy. The "detection problem" is particularly challenging for low amplitude signals embedded in "glitchy" instrument noise. It is imperative that we can robustly distinguish between the data being consistent with instrument noise alone, or noise and a weak gravitational wave signal. In response to this challenge we have set out to develop a robust, general purpose approach that can locate and characterize gravitational wave signals, and provided odds that the signal is of cosmic origin. Our approach employs the Markov Chain Monte Carlo family of algorithms to construct a fully Bayesian solution to the challenge - the Parallel Tempered Markov Chain Monte Carlo (PTMCMC) detection algorithm. The PTMCMC detection algorithm establishes which regions of parameter space contain the highest posterior weight, efficiently explores the posterior distribution function of the model parameters, and calculates the marginalized likelihood, or evidence, for the models under consideration. We illustrate our approach using simulated LISA and LIGO-Virgo data.
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Killbourn, Stuart Duncan. "Double pendulums for terrestrial interferometric gravitational wave detectors." Thesis, University of Glasgow, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362943.
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Husman, Matthew Edward. "Suspension and control for interferometric gravitational wave detectors." Thesis, University of Glasgow, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312701.
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Watkins, William John. "A prototype system for gravitational wave data analysis." Thesis, Cardiff University, 1991. http://orca.cf.ac.uk/106311/.
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This thesis is concerned with a prototype gravitational wave data analysis system. Work will shortly be underway on the construction of large scale broad-band laser interferometers that should produce data containing gravitational waves. Subsequently, systems that can analyse this data, extracting any waves within the noise, need to be developed now. The prototype system described in this thesis is the first fully automated gravitational wave data analysis system to be developed. It is designed in parallel, to run on several processors simultaneously, as future systems are certain to employ parallelism to some degree. This thesis is also concerned with the analysis of actual data by this system, produced by the prototype interferometer owned and operated by the University of Glasgow. The software is described in detail, beginning with a description of the parallelism within the system. The procedure employed to split the multiplexed data into its constituent streams is discussed followed by a description of the methods employed to optimise the detector noise for the extraction of possible signals from short duration gravitational wave bursts. This is followed by a description of both the statistical analysis and the search for events carried out on the calibrated and optimally weighted interferometer stream. This search looks for wideband burst events in the time series and also coalescing binary signals found by cross-correlating the noise with a bank of templates. An account of the results of the analysis is given, concentrating on the statistics of detector noise, identifying its main characteristics both when the detector is operating properly and also when the housekeeping data suggests it is not. A description is given of a parameter, easily calculated from the noise, that is shown to be a good diagnostic indicator of the state of the detector. The distribution of events found by the analysis is discussed, and it is shown how the number of events vary with the state of the detector.
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Mavalvala, Nergis. "Alignment issues in laser interferometric gravitational-wave detectors." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/10769.
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Buikema, Aaron. "High-power operation of interferometric gravitational-wave detectors." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/128328.
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This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, February, 2020
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 157-172).
With the conclusion of the first two observing runs of the Advanced LIGO detectors, which saw the first direct detection of gravitational waves, we are firmly in the era of gravitational-wave astronomy. To reach the highest sensitivities, current interferometric gravitational-wave detectors are designed for hundreds of kilowatts of circulating optical power. At these high circulating powers, the sensitivity of the detectors to gravitational waves will be limited by the quantum properties of the light: shot noise at frequencies above ~ 100 Hz, and quantum radiation pressure noise at lower frequencies. To reach the high powers necessary for achieving the quantum noise limits imposed by the light, it is essential to solve the control problems and understand the additional noise introduced by high power operation. Additionally, development of high-power laser sources that reach the stringent noise and reliability requirements is crucial. This work comprises three experiments aimed at reaching the radiation-pressure-dominated regime of interferometric gravitational-wave detectors. The first part presents results from a high-power, meter-long Fabry-Prot Michelson interferometer to probe classical and quantum radiation pressure effects using a gram-scale mechanical oscillator. The second part is an exploration of the effects of electric fields and charging of test masses on the sensitivity of the LIGO detectors, which may limit the ability to observe radiation-pressure effects. Finally, we describe the development and characterization of a high-power, narrow-linewidth ytterbium-doped fiber amplifier for use in future gravitational-wave detectors.
by Aaron Buikema.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Physics
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Rao, Shanti Raja Libbrecht Kenneth George. "Mirror thermal noise in interferometric gravitational wave detectors /." Diss., Pasadena, Calif. : California Institute of Technology, 2003. http://resolver.caltech.edu/CaltechETD:etd-05092003-153759.
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Wise, Stacy M. "Sensitivity enhancement in future interferometric gravitational wave detectors." [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0013804.
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Degallaix, Jerome. "Compensation of strong thermal lensing in advanced interferometric gravitational waves detectors." University of Western Australia. School of Physics, 2006. http://theses.library.uwa.edu.au/adt-WU2006.0060.
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A network of laser interferometer gravitational waves detectors spread across the globe is currently running and steadily improving. After complex data analysis from the output signal of the present detectors, astrophysical results begin to emerge with upper limits on gravitational wave sources. So far, however no direct detection has been announced. To increase the sensitivity of current detectors, a second generation of interferometers is planned which will make gravitational wave astronomy a reality within one decade. The advanced generation of interferometers will represent a substantial upgrade from current detectors. Especially, very high optical power will circulate in the arm cavities in order to reduce by one order of magnitude the shot noise limited sensitivity in high frequency. However, the theoretical shot noise limit will only be achieved after implementation of complex thermal lensing compensation schemes. Thermal lensing is direct consequence of the residual optical absorption inside the substrate and coating of the test masses and could have tragic consequences for the functionality of the interferometer. The Australian Consortium for Interferometric Gravitational Astronomy (ACIGA) in collaboration with LIGO will run a series of high optical power tests to understand the characteristics and effects of thermal lensing. During these tests, techniques to compensate thermal lensing will be experimented. This thesis mainly focused on the first high optical power test in Gingin, Australia. The first test will consist of a Fabry Perot cavity with the sapphire substrate of the input mirror inside the cavity. Due to the high optical circulating power a strong convergent thermal lens will appear in the input mirror substrate. Because of the presence of the thermal lens inside the cavity, the size of the cavity waist will be reduced and the cavity circulating power will decrease. Simulations using higher order mode expansion and FFT propagation code were completed to estimate ways to compensate strong thermal lensing for the Gingin first test. The term `strong thermal lensing? is used because the thermal lens focal length is comparable to the design focal length of the optical components. The expected performance of a fused silica compensation plate is presented and advantages and limits of this method are discussed. Experimental results on small scale actuators which can potentially compensate thermal lensing are detailed. The knowledge gained from these experiments was valuable to design the real scale compensation plate which was used in the first Gingin test. This test was carried at the end of 2005. The thermal lens due to 1 kW of optical power circulating in the sapphire substrate was successfully compensated using a fused silica plate. Yet, thermal lensing compensation may only be required for room temperature advanced interferometer. Indeed, we showed that cooling the interferometer mirror to cryogenic temperature can eliminate the thermal lensing problem and also substantially decrease the mirror thermal noise.
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Gras, Slawomir M. "Opto-acoustic interactions in high power interferometric gravitational wave detectors." University of Western Australia. School of Physics, 2009. http://theses.library.uwa.edu.au/adt-WU2010.0093.
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[Truncated abstract] Advanced laser interferometer gravitational wave detectors require an extremely high optical power in order to improve the coupling between the gravitational wave signal and the optical field. This high power requirement leads to new physical phenomena arising from nonlinear interactions associated with radiation pressure. In particular, detectors with multi-kilometer-long arm cavities containing high density optical fields suffer the possibility of 3-mode opto-acoustic interactions. This involves the process where ultrasonic vibrations of the test mass cause the steady state optical modes to scatter. These 3-mode interactions induce transverse optical modes in the arm cavities, which then can provide positive feedback to the acoustic vibrations in the test masses. This may result in the exponential growth of many acoustic mode amplitudes, known as Parametric Instability (PI). This thesis describes research on 3-mode opto-acoustic interactions in advanced interferometric gravitational wave detectors through numerical investigations of these interactions for various interferometer configurations. Detailed analysis reveals the properties of opto-acoustic interactions, and their dependence on the interferometer configuration. This thesis is designed to provide a pathway towards a tool for the analysis of the parametric instabilities in the next generation interferometers. Possible techniques which could be helpful in the design of control schemes to mitigate this undesirable phenomenon are also discussed. The first predictions of parametric instability considered only single interactions involving one transverse mode and one acoustic mode in a simple optical cavity. ... In Chapter 6, I was able to make use of a new analytical model due to Strigin et al., which describes parametric instability in dual recycling interferometers. To make the solution tractable, it was necessary to consider two extreme cases. In the worst case, recycling cavities are assumed to be resonant for all transverse modes, whereas in the best cases, both recycling cavities are anti-resonant for the transverse modes. Results show that, for the worst case, parametric gain values as high as ~1000 can be expected, while in the best case the gain can be as low as ~ 3. The gain is shown to be very sensitive to the precise conditions of the interferometer, emphasising the importance of understanding the behaviour of the detectors when the cavity locking deviates from ideal conditions. Chapter 7 of this thesis contains work on the observation of 3-mode interactions in an optical cavity at Gingin, which confirms the analysis presented here, and also a paper which shows how the problem of 3-mode interactions can be harnessed to create new devices called opto-acoustic parametric amplifiers. In the conclusions in Chapter 8, I discuss the next important steps in understanding parametric interactions in real interferometers including the need for more automated codes relevant to the design requirements for recycling cavities. In particular, it is pointed out how the modal structure of power and signal recycling cavities must be understood in detail, including the Gouy phase for each transverse mode, to be able to obtain precise predictions of parametric gain. This thesis is organised as a series of papers which are published or have been submitted for publication. Such writing style fills the condition for Ph.D. thesis at the University of Western Australia.
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Serrano, Moral Ma Ángeles (María Ángeles). "The motion sensing problem in spherical gravitational wave detectors." Doctoral thesis, Universitat de Barcelona, 1999. http://hdl.handle.net/10803/667748.
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La tesis presenta una cuidadosa descripción del comportamiento dinámico de las antenas esféricas resonantes de ondas gravitatorias cuando son excitadas por radiación gravitatoria, o también por señales de calibración, centrando especialmente la atención en el problema de los resonadores y desarrollando un procedimiento general aplicable a cualquier propuesta.
La primera parte del trabajo incluye los preliminares y una breve supervisión de la teoría de Radiación Gravitatoria según la Relatividad General. La atención se centra luego en la Detección de Ondas Gravitatorias, y se describe el estado actual revisando las diversas técnicas, especialmente la detección resonante con detectores esféricos.
El resto de la tesis se dedica exclusivamente a estos últimos, que se consideran como un sistema acoplado esfera-resonadores. Se establecen el conjunto de ecuaciones diferenciales que describen el sistema bajo suposiciones generales, y se restringen a una situación ideal. Su resolución en base a series perturbativas proporciona las resonancias del dispositivo acoplado, así como las amplitudes vibracionales en las posiciones de los resonadores. También se discute la posibilidad de construcción de canales de modo.
A continuación, presentamos nuestra propuesta PHCA, que como la antena TIGA presenta una distribución mínima interesante de resonadores, y se analizan ambas propuestas como particularizaciones de los resultados generales.
FInalmente, emprendemos el tratamiento de otras dos cuestiones importantes: como pequeñas desviaciones de la situación ideal afectan las respuestas del sistema, y el problema de la deconvolución de señales, también cuando se tiene en cuenta la presencia de ruido. El primer tema es especialmente interesante por incrementar el grado de aplicabilidad del modelo ideal a sistemas reales. La memoria se cierra con una breve discusión sobre los resultados.
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Heinzel, Gerhard. "Advanced optical techniques for laser interferometric gravitational wave detectors." [S.l. : s.n.], 1999. http://deposit.ddb.de/cgi-bin/dokserv?idn=956318886.
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Gerosa, Davide. "Source modelling at the dawn of gravitational-wave astronomy." Thesis, University of Cambridge, 2016. https://www.repository.cam.ac.uk/handle/1810/261557.
Full textAbstract:
The age of gravitational-wave astronomy has begun. Gravitational waves are propagating spacetime perturbations ($\textit{“ripples in the fabric of space-time”}$) predicted by Einstein’s theory of General Relativity. These signals propagate at the speed of light and are generated by powerful astrophysical events, such as the merger of two black holes and supernova explosions. The first detection of gravitational waves was performed in 2015 with the LIGO interferometers. This constitutes a tremendous breakthrough in fundamental physics and astronomy: it is not only the first direct detection of such elusive signals, but also the first irrefutable observation of a black-hole binary system. The future of gravitational-wave astronomy is bright and loud: the LIGO experiments will soon be joined by a network of ground-based interferometers; the space mission eLISA has now been fully approved by the European Space Agency with a proof-of-concept mission called LISA Pathfinder launched in 2015. Gravitational-wave observations will provide unprecedented tests of gravity as well as a qualitatively new window on the Universe. Careful theoretical modelling of the astrophysical sources of gravitational-waves is crucial to maximize the scientific outcome of the detectors. In this Thesis, we present several advances on gravitational-wave source modelling, studying in particular: (i) the precessional dynamics of spinning black-hole binaries; (ii) the astrophysical consequences of black-hole recoils; and (iii) the formation of compact objects in the framework of scalar-tensor theories of gravity. All these phenomena are deeply characterized by a continuous interplay between General Relativity and astrophysics: despite being a truly relativistic messenger, gravitational waves encode details of the astrophysical formation and evolution processes of their sources. We work out signatures and predictions to extract such information from current and future observations. At the dawn of a revolutionary era, our work contributes to turning the promise of gravitational-wave astronomy into reality.
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Dixon, George. "The mechanical stability of instrumentation for gravitational wave detection." Thesis, University of Birmingham, 2011. http://etheses.bham.ac.uk//id/eprint/1770/.
Full textAbstract:
This thesis opens with a brief review of the aspects of gravitational waves which are relevant for detector design and engineering, and an introduction to the LISA and LISA Pathfinder missions. The thesis describes original work carried out to support the LISA Pathfinder mission at the University of Birmingham. The salient space mission quality requirements and mission specific technical and documentation requirements are set out. The classical and computer based mechanical analysis, birefringence optical inspections, and linear elastic fracture mechanics and fracture control engineering which were applied to support flight acceptance of the brittle glass-ceramic optical bench interferometer structure are presented. The design of a new photodiode mount is shown and justified, while the mechanical, optical, and electrical analysis, electrical and optical testing and, finally, the installation and alignment of the photodiodes are presented.
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Lawrence, Ryan Christopher 1975. "Active wavefront correction in laser interferometric gravitational wave detectors." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/29308.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2003.Includes bibliographical references (p. 239-243).
As the first generation of laser interferometric gravitational wave detectors near operation, research and development has begun on increasing the instrument's sensitivity while utilizing existing infrastructure. In the Laser Interferometer Gravitational Wave Observatory (LIGO), significant improvements are being planned for installation in 2007 to increase the sensitivity to test mass displacement, hence sensitivity to gravitational wave strain, by improved suspensions and test mass substrates, active seismic isolation, and higher input laser power. Even with the highest quality optics available today, however, finite absorption of laser power within transmissive optics, coupled with the tremendous amount of optical power circulating in various parts of the interferometer, result in critical wavefront deformations which will cripple the performance of the instrument. Discussed is a method of active wavefront correction via direct thermal actuation on optical elements of the interferometer; or, "thermally adaptive optics". A simple nichrome heating element suspended off the face of an affected optic will, through radiative heating, remove the gross axisymmetric part of the original thermal distortion. A scanning heating laser- will then be used to remove any remaining non-axisymmetric wavefront distortion, generated by inhomogeneities in the substrate's absorption, thermal conductivity, etc. This work includes a quantitative analysis of both techniques of thermal compensation, as well as the results of a proof-of-principle experiment which verified the technical feasibility of each technique.
by Ryan Christopher Lawrence.
Ph.D.
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Blackburn, Lindy L. "Open Issues in the search for gravitational wave transients." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/68965.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 193-201).
The LIGO-Virgo network of kilometer-scale laser interferometric gravitational-wave detectors reached a major milestone with the successful operation of LIGO's fifth (S5) and Virgo's first (VSR1) science runs during 2005-2007. This thesis presents several issues related to gravitational-wave transient detection from the perspective of the joint all-sky, un-triggered burst search over S5/VSR1 data. Existing searches for gravitational-wave bursts must deal with the presence of non-Gaussian noise transients which populate the data over the majority of sensitive signal space. These events may be confused with true signals, and are the current limiting factor in search sensitivity and detection confidence for any real event. The first part of this thesis focuses on the development of tools to identify, monitor and characterize these instrumental disturbances in LIGO and Virgo data. An automated procedure is developed and applied to the S5/VSR1 search in order to safely remove noise transients from the analysis without sacrificing sensitivity by making use of the wealth of auxiliary information recorded by the detectors. The second part of this thesis focuses on the interpretation of outlier events in the context of a non-Gaussian, non-stationary background. An extensive follow-up procedure for candidate gravitational-wave events is developed and applied to a single burst outlier from the S5/VSR1 search, later revealed to be a blind simulation injected into the instruments. While the follow-up procedure correctly finds no reason to reject the candidate as a possible gravitational wave, it highlights the difficulty in making a confident detection for signals with similar waveform morphology to common instrumental disturbances. The follow-up also deals with the problem of objectively defining the significance of a single outlier event in the context of many semi-disjoint individual searches. To address this, a likelihood-ratio based unified ranking is developed and tested against the original procedures of the S5/VSR1 burst search. The new ranking shows a factor of four improvement in the statistical significance of the outlier event, and a 12% reduction using fixed thresholds and 38% reduction using a loudest event statistic for a rate upper limit on a mock signal population.
by Lindy L. Blackburn
Ph.D.