Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 18 of 18 for “"Scalar-Tensor"”.
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Compact Objects In Relativistic Theories Of Gravity
… generalization of general relativity: scalar-tensor theory. We start by considering theories where gravity is mediated by a single extra scalar degree of freedom (in addition to the metric tensor). An interesting class of scalar-tensor theories passes all experimental tests in the …
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Alternative theories of gravity and their application to cosmology
… of some cosmological models resulting from scalar-tensor and higher-order theories of gravity. We use the dynamical systems approach with non–compact expansion normalised variables to study the isotropisation of Bianchi type I models in Rn–gravity. We find that these type of models can …
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Analytic Modelling of Gravitational-Wave Source in General Relativity and Alternative Theories of Gravity
… theory of gravity the so-called massless scalar-tensor theory. More specifically, we describe the map of the dynamics of a binary system in scalar-tensor theory into the EOB formalism by building upon the PN expanded Lagrangian of the two-body problem at 3PN order. We discuss the …
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Neutron Star Models in Alternative Theories of Gravity
… theories of gravity. In particular, we focus on Scalar-Tensor theories and <italic>f(R)<italic> theories of gravity. We construct static and slowly rotating numerical star models for a set of equations of state, including a polytropic model and more realistic equations of state motivated by …
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Testing General Relativity with the next generation of cosmological surveys
… In this analysis, we investigate the Horndeski scalar-tensor theories and beyond which has been recently described in the generilized dark energy (DE) or scalar-tensor paradigm - dubbed unified dark energy (UDE). This applies the 3+1 Arnowitt-DeserMisner (ADM) formalism where a general action in …
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Tests of Gravity Theories with Pulsar Timing
… tighter constraints on the parameter space of Scalar-Tensor gravity theories as the most promising candidates among many alternative gravity theories. <br /><br /> In addition, we investigate the possible detection of a pulsar orbiting in the vicinity of the supermassive black hole SgrA∗ . We …
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Gravitational Waves and Inspiraling Compact Binaries in Alternative Theories of Gravity
… theories to general relativity known as scalar-tensor theories. For the conservative part of the motion, we obtain the two-body Lagrangian and conserved energy and momentum through second post-Newtonian order. We find the contributions to gravitational radiation reaction to 1.5 …
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Heterotic Braneworld Gravity
… separated by the 11th dimension with a scalar field in the bulk. In this dissertation we review some of the alternative theories of gravity, including the Kaluza-Klein model as an early example of a theory featuring extra dimensions, and the more recent braneworld models, in particular …
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Source modelling at the dawn of gravitational-wave astronomy
… 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 …
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Constraining gravitational and cosmological parameters with astrophysical data
… for viable theories of gravity where the Ricci scalar R in the Lagrangian is replaced by an arbitrary function f(R). Making use of the equivalence between such theories and scalar-tensor gravity, we find that models can be made consistent with solar system constraints either by giving the scalar …
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Dynamics of primordial phase transitions, primordial magnetic fields, and Big Bang nucleosynthesis
… problems are probed in the framework of scalar-tensor theories of gravity. An extended inflationary cosmological model has been proposed.
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Gravitational collapse, compact objects and gravitational waves in General Relativity and modified gravity
… most popular candidates for modified gravity, Scalar Tensor (ST) theories, as well as look for smoking-gun signatures. We analyse the formation of compact objects from core collapse simulations of stars in massive ST theories over the astrophysically plausible range of stellar progenitor masses …
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Motion in a scalar field
Light scalar fields emerge as a generic prediction in physics beyond the Standard Model. For example, they arise as new degrees of freedom in modified gravity, as Kaluza-Klein modes from extra compactified dimensions, and as Nambu-Goldstone bosons from spontaneously broken symmetries. Far from …
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Galaxy-Scale Signatures of Screened Modified Gravities
… years, theories of gravity incorporating a scalar field coupled to gravity---'scalar-tensor' theories---have been subject to increased attention. In these theories, the scalar field mediates gravitational-strength 'fifth forces'. For such scalar fields to retain cosmological relevance while …
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Effective Field Theories in Cosmology
<p>During the last 20 years, a large amount of detailed cosmological observations have promoted cosmology to the rank of high-precision science. Remarkably, all the observations currently available can be accounted for by assuming that (<em>i</em>) the universe is approximately homogeneous and …
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Uncovering gravitational wave signatures of modified theories of gravity and exotic matter
… study of binary black holes in Einstein-scalar-Gauss-Bonnet (EsGB) theory of gravity in the decoupling limit. An interesting feature of this theory is that black holes can posses scalar hair and the resulting gravitational-wave signals -- scalar polarisation. By focusing on the ringdown …
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Astrophysical tests of modified gravity
… theories of screened modified gravity which are scalar-tensor theories where the field is conformally coupled to matter via the metric and includes chameleon and symmetron models as well as those that screen using the environment-dependent Damour-Polyakov effect. The thesis is split into two …