We report the results of a Dark Energy Camera optical follow-up of the gravitational-wave (GW) event GW151226, discovered by the Advanced Laser Interferometer Gravitational-wave Observatory detectors. Our observations cover 28.8 deg(2) of the localization region in the i and z bands (containing 3% of the BAYESTAR localization probability), starting 10 hr after the event was announced and spanning four epochs at 2-24 days after the GW detection. We achieve 5 sigma point-source limiting magnitudes of i approximate to 21.7 and z approximate to 21.5, with a scatter of 0.4 mag, in our difference images. Given the two-day delay, we search this area for a rapidly declining optical counterpart with greater than or similar to 3 sigma significance steady decline between the first and final observations. We recover four sources that pass our selection criteria, of which three are cataloged active galactic nuclei. The fourth source is offset by 5.8 arcsec from the center of a galaxy at a distance of 187 Mpc, exhibits a rapid decline by 0.5 mag over 4 days, and has a red color of i - z approximate to 0.3 mag. These properties could satisfy a set of cuts designed to identify kilonovae. However, this source was detected several times, starting 94 days prior to GW151226, in the Pan-STARRS Survey for Transients (dubbed as PS15cdi) and is therefore unrelated to the GW event. Given its long-term behavior, PS15cdi is likely a Type IIP supernova that transitioned out of its plateau phase during our observations, mimicking a kilonova-like behavior. We comment on the implications of this detection for contamination in future optical follow-up observations.

In the present work we study gravitational waves in the approximation of high frequency, and their interaction with matter waves with comparable frequency. We generalize the formalism of R. A. Isaacson to the case of non-vacuum spacetimes. We formulate and study a technique of so called averaging, which helps us to separate slow changes and high-frequency fluctuations of various tensor fields. The described methods are used in examples with a given particular metric - so called background metric. We thus study the interaction of high-frequency gravitational waves on the Robinson- Trautman background and the high-frequency electromagnetic waves. Further, we seek a perfect fluid with high-frequency energy-momentum tensor that could coexist with high-frequency gravitational waves on the flat Friedmann-Lemaˆıtre-Robertson-Walker background; again, we examine the relation between those potential gravitational and matter waves.

No description available.

by Lai Chi Wai. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references (leaves [104]-107). / Text in English; abstract also in Chinese. / by Lai Chi Wai. / Abstract --- p.i / Acknowledgment --- p.iv / List of Figures --- p.xi / List of Tables --- p.xii / Chapter 1 --- Introduction to Numerical Relativity --- p.1 / Chapter 1.1 --- The need for numerical approach --- p.2 / Chapter 1.2 --- A brief history of numerical relativity --- p.3 / Chapter 1.3 --- What this thesis concern --- p.4 / Chapter 2 --- Mathematical Formulation --- p.6 / Chapter 2.1 --- The initial value problem --- p.6 / Chapter 2.2 --- The space-plus-time (3+1) formalism --- p.8 / Chapter 3 --- Methods in Numerical Relativity --- p.17 / Chapter 3.1 --- General numerical methods --- p.17 / Chapter 3.2 --- Consistency and stability --- p.18 / Chapter 3.3 --- Difficulties and limitations --- p.20 / Chapter 3.4 --- Strategies specific to numerical relativity --- p.21 / Chapter 3.5 --- Boundary conditions --- p.27 / Chapter 4 --- Detweiler's Scheme --- p.29 / Chapter 4.1 --- Constrainted evolution in numerical relativity --- p.29 / Chapter 4.2 --- Detweiler's Scheme --- p.31 / Chapter 5 --- Constraint Enforcement in Plane Waves --- p.36 / Chapter 5.1 --- General solution for a linearized plane wave --- p.36 / Chapter 5.2 --- Code test --- p.40 / Chapter 5.3 --- Comparison of results with and without Detweiler's scheme --- p.41 / Chapter 5.4 --- Stability of evolution --- p.46 / Chapter 5.5 --- Comparison of Detweiler's scheme and simple diffusion method --- p.50 / Chapter 5.6 --- Two parameter extension of Detweiler's scheme --- p.55 / Chapter 5.7 --- Long time behavior --- p.59 / Chapter 5.8 --- Comparison of Hamiltonian and momentum constraint --- p.63 / Chapter 5.9 --- Indicator of Detweiler's scheme --- p.67 / Chapter 5.10 --- The maximal slicing condition --- p.70 / Chapter 5.11 --- The leaking problem --- p.73 / Chapter 5.12 --- The near-linear plane waves --- p.75 / Chapter 6 --- Constraint Enforcement in MTW Waves --- p.83 / Chapter 6.1 --- MTW waves --- p.83 / Chapter 6.2 --- Linear regime --- p.85 / Chapter 6.3 --- Comparison of results with and without Detweiler's scheme --- p.85 / Chapter 6.4 --- The indicator --- p.90 / Chapter 6.5 --- A comparison of simple diffusion method and Detweiler's scheme with a large amplitude wave --- p.92 / Chapter 7 --- Summary and Conclusion --- p.97 / Chapter A --- The Numerical Scheme of the Code --- p.98 / Chapter B --- Convergence Test --- p.100 / Chapter B.1 --- Plane wave --- p.100 / Chapter B.2 --- MTW wave --- p.102 / Bibliography --- p.104

Orientadores: Cecilia Bertoni Martha Hadler Chirenti, Ernesto Kemp / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-09-03T00:23:17Z (GMT). No. of bitstreams: 1 Souza_GibranHenriqueDe_D.pdf: 9537099 bytes, checksum: 8b4790f32975067863cff845c7c37170 (MD5) Previous issue date: 2017 / Resumo: No presente trabalho focamos na descrição das oscilações da crosta de estrelas de nêutrons que apresentam um campo magnético poloidal com uma componente toroidal, onde utilizamos de oito equações de estado para descrever a matéria constituinte destas estrelas de nêutrons. Para isso apresentamos todo o formalismo matemático para descrever a estrutura interna, rotação, campo magnético e perturbações no fluido necessário para a apresentação dos resultados obtidos. Paralelo a isso efetuamos a extensão dos resultados obtidos na dissertação de mestrado, onde foi apresentado o cálculo das características das ondas gravitacionais do modo-f, como frequência de oscilação e tempo de decaimento. Aqui estendemos os resultados anteriormente obtidos com a inclusão de novas equações de estado e o teste da validade das chamadas relações universais / Abstract: In the present work we focus on the description of the crustal oscillations of neutron stars that present a poloidal magnetic field with a toroidal component, where we use eight equations of state to describe the constituent matter of these neutron stars. For this, we developed all the mathematical formalism to describe the internal structure, rotation, magnetic field and perturbations in the fluid necessary for the presentation of the obtained results. Parallel to this, we extended the results obtained in the student's master dissertation, where the calculation of the characteristics of the f-mode gravitational waves was presented, such as oscillation frequency and decay time. Here we extend the previously obtained results with the inclusion of new state equations and the test of the validity of the so-called universal relations / Doutorado / Física / Doutor em Ciências / 140838/2013-9 / CNPQ

In the present monograph we study in detail the primordial gravitational waves in cosmologies with a decaying vacuum. The decaying vacuum models are an alternative to solve the cosmological constant problem attributing a dynamic to the vacuum energy. The problem of primordial gravitational waves is discussed in the framework of an expanding, flat, spatially homogeneous and isotropic FLRW Universe described by General Relativity theory with decaying vacuum energy density of the type $\\Lambda \\equiv \\Lambda(H)$. Two particular interesting limits of a class of decaying vacuum models were investigated. A first-order tensor perturbation term was introduced to the FLRW metric, the evolution equation of the perturbations was derived and then expressed in terms of a Fourier expansion, the time-dependent part decouples from the spatial part. The resulting equation has the form of a damped harmonic oscillator which depends on the scale factor, which carries all the cosmological and decaying vacuum characteristics. In the first model studied, the decaying vacuum has the form $\\Lambda \\propto H^2$. The gravitational wave equation is established and its time-dependent part has analytically been solved for different epochs in the case of a flat geometry. The main result is unlike the standard $\\Lambda$CDM cosmology (no interacting vacuum): in this model there is gravitational wave amplification during the radiation era, which in quantum field theory means graviton production. This difference is a clear signature of the decaying vacuum models which a eventual observation could give empirical clues about it. However, high frequency modes are damped out even faster than in the standard cosmology, both in the radiation and matter-vacuum dominated epoch. The physical gravitational wave quantities like the modulus of the mode function, power and gravitational wave energy density spectra generated at different cosmological eras are also explicitly evaluated. The second model studied is a decaying vacuum of the form $\\Lambda \\propto H^3$. This model drives a nonsingular flat cosmology which is termed complete in the sense that the cosmic evolution occurs between two extreme de Sitter stages. The particularity which makes interesting this model is that the transition from the early de Sitter era to the radiation phase is smooth avoiding the graceful exit problem. The gravitational wave equation is derived and its time-dependent part numerically integrated in a relevant period previously delimited. The gravitational wave solutions for the other eras were calculates analytically. Today\'s gravitational wave spectra were calculated and compared with the standard result where an abrupt transition is assumed. It is found that the stochastic background of gravitational waves is very similar to the one predicted by the cosmic concordance model plus inflation except for the higher frequencies. / Na presente monografia foi estudado em detalhe as ondas gravitacionais primordiais em cosmologias com decaimento do vácuo. Os modelos de decaimento do vácuo são uma alternativa para resolver o problema da constante cosmológica atribuindo uma dinâmica à energia do vácuo. O problema de ondas gravitacionais primordiais é discutida no âmbito de um Universo FLRW em expansão, plano, espacialmente homogêneo e isotrópico descrito pela teoria da Relatividade Geral com decaimento da densidade de energia do vácuo do tipo $\\Lambda \\equiv \\Lambda(H)$. Dois limites particularmente interessantes de uma classe de modelos de decaimento do vácuo foram trabalhados. Um termo tensorial perturbativo a primeira ordem foi introduzido na métrica de FLRW, a equação de evolução das perturbações foi derivada e depois expressada em termos de uma expansão de Fourier, a parte dependente do tempo desacopla-se da parte espacial. A equação resultante tem a forma de um oscilador harmônico amortecido que depende do fator de escala que carrega todas as características cosmológicos e do decaimento do vácuo. No primeiro modelo estudado, o decaimento do vácuo tem a forma $\\Lambda \\propto H^2$. A equação da onda gravitacional é estabelecida e a sua parte dependente do tempo foi resolvida analiticamente para diferentes épocas no caso de uma geometria plana. O resultado principal é que a diferença da cosmologia $\\Lambda$CDM padrão (sem decaimento do vácuo), neste modelo ocorre amplificação de ondas gravitacionais durante a era de radiação, que em mecânica quântica significa produção gráviton. Esta diferença é uma assinatura clara dos modelos de decaimento do vácuo que uma eventual observação poderia dar pistas empíricas sobre o assunto. No entanto, os modos de alta frequência são amortecidos ainda mais rápido do que na cosmologia padrão, tanto na era da radiação e da matéria-vácuo. As quantidades físicas das ondas gravitacionais, como o módulo da função de modos, espectros de potência e de densidade de energia de onda gravitacional geradas em diferentes eras cosmológicas também foram avaliadas explicitamente. O segundo modelo estudado é um decaimento do vácuo da forma $\\Lambda \\propto H^3$. Este modelo leva uma cosmologia plana não singular que é denominado completo no sentido de que a evolução cósmica ocorre entre duas eras de Sitter extremas. A particularidade que torna interessante este modelo é que a transição do início da era de Sitter era para a fase da radiação é suave evitando o graceful exit problem. A equação gravitacional é derivada e sua parte dependente do tempo foi integrada numericamente num período relevante previamente delimitado, as soluções das ondas gravitacionais para as outras eras foram calculadas analiticamente. Os espectros de hoje das ondas gravitacionais foram calculados e comparados com os cálculos padrão onde é assumida uma transição abrupta. Verificou-se que o fundo estocástico de ondas gravitacionais é muito semelhante ao previsto pelo modelo de concordância cósmica mais a inflação, exceto para as frequências mais altas.

Zhang, Yaojun = / "November 2009." / Thesis (M.Phil.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (p. 109-111). / Abstracts in English and Chinese. / Zhang, Yaojun = / Abstract --- p.i / Acknowledgement --- p.iv / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Quasi-Normal Modes of Neutron Stars --- p.6 / Chapter 2.1 --- Equilibrium State of a Neutron Star --- p.6 / Chapter 2.2 --- Fluid Displacement and Metric Perturbation --- p.8 / Chapter 2.3 --- Axial Oscillations of Neutron Stars --- p.9 / Chapter 2.3.1 --- Wave Equation inside the Star --- p.9 / Chapter 2.3.2 --- Wave Equation outside the Star --- p.10 / Chapter 2.3.3 --- Location of Quasi-normal Modes --- p.10 / Chapter 2.4 --- Polar Oscillations of Neutron Stars - LD Formalism --- p.12 / Chapter 2.4.1 --- Equations inside the Star --- p.12 / Chapter 2.4.2 --- Equations outside the Star --- p.14 / Chapter 2.4.3 --- Location of Quasi-normal Modes --- p.16 / Chapter 2.5 --- Polar Oscillations of Neutron Stars - AAKS Formalism --- p.16 / Chapter 2.5.1 --- Equations inside the Star --- p.16 / Chapter 2.5.2 --- Equations outside the Star --- p.19 / Chapter 2.5.3 --- Location of Quasi-normal Modes --- p.19 / Chapter 3 --- Decoupling of Spacetime Oscillations and Fluid Motion --- p.21 / Chapter 3.1 --- Motivation of Decoupling --- p.21 / Chapter 3.2 --- Expressing F in terms of S and H --- p.21 / Chapter 3.2.1 --- Inside the Star --- p.22 / Chapter 3.2.2 --- Outside the Star --- p.25 / Chapter 3.3 --- Constraint-free AAKS Formalism --- p.25 / Chapter 3.3.1 --- Equations inside the Star --- p.25 / Chapter 3.3.2 --- Equations outside the Star --- p.27 / Chapter 3.4 --- Cowling Approximation for Polar p-Mode --- p.29 / Chapter 3.4.1 --- Independent Fluid Motion --- p.29 / Chapter 3.4.2 --- Location of Polar p-Modes --- p.30 / Chapter 3.4.3 --- Numerical Results and Discussion --- p.31 / Chapter 3.5 --- Inverse-Cowling approximation for ω-Mode --- p.33 / Chapter 3.5.1 --- Independent Spacetime Oscillations --- p.33 / Chapter 3.5.2 --- Location of ω-Modes --- p.34 / Chapter 3.5.3 --- Numerical Results and Discussion --- p.34 / Chapter 4 --- Interplay between Matter and Spacetime --- p.37 / Chapter 4.1 --- Physical Insight --- p.37 / Chapter 4.2 --- Sturm-Liouville Eigenvalue Problem --- p.39 / Chapter 4.3 --- Energy of the Fluid --- p.40 / Chapter 4.4 --- Spacetime Oscillation Driven by Fluid Motion --- p.45 / Chapter 4.5 --- Damped Oscillation Caused by Radiation of Gravitational Wave --- p.46 / Chapter 4.6 --- Calculation of δωn in a Perturbative Way --- p.48 / Chapter 4.7 --- Numerical Results and Discussion --- p.49 / Chapter 5 --- Asymptotic Behavior of Spacetime Modes --- p.61 / Chapter 5.1 --- Motivation --- p.61 / Chapter 5.2 --- Asymptotic Behavior of Axial ω-modes for One-Layered Stars --- p.62 / Chapter 5.2.1 --- "Asymptotic Form of g(r*,ω)" --- p.63 / Chapter 5.2.2 --- "Asymptotic Form of f(r*, ω)" --- p.67 / Chapter 5.2.3 --- Asymptotic Behavior of Axial Quasi-Normal Modes --- p.69 / Chapter 5.3 --- Asymptotic Behavior of Polar ω-modes for One-Layered Stars --- p.71 / Chapter 5.3.1 --- High-Frequency Approximation --- p.71 / Chapter 5.3.2 --- Asymptotic Behavior of Polar Quasi-Normal Modes --- p.73 / Chapter 5.4 --- Relationship between Axial and Polar ω-Modes --- p.74 / Chapter 5.4.1 --- Application 1:ω-Modes of Quark Stars --- p.75 / Chapter 5.4.2 --- Application 2:ω-Modes of Polytropic Stars --- p.80 / Chapter 5.4.3 --- Application 3: The Influence of Surface Discontinuities --- p.89 / Chapter 5.4.4 --- Application 4:ω-Modes of Realistic Neutron Stars --- p.92 / Chapter 6 --- Conclusion and Outlook --- p.99 / Chapter A --- From Einstein Equation to LD Formalism --- p.101 / Chapter A.l --- The Linearized Perturbation Equations --- p.101 / Chapter A.1.1 --- The Perturbation of the Einstein Tensor --- p.102 / Chapter A.1.2 --- The Perturbation of the Energy-momentum Tensor --- p.103 / Chapter A.1.3 --- The Perturbed Einstein Equations --- p.104 / Chapter A.2 --- Some Symbolic Operation Results --- p.105 / Chapter A.3 --- Simplifications --- p.106

Thesis (Ph. D.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references (leaves 62-63). Also available on the Internet.

Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (p. 205-211).

Thesis (Ph. D.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references (leaves 62-63). Also available on the Internet.