Constraining scalar-tensor theories of gravity through observations
Anderson, David Sutton
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Scalar-tensor theories of gravity have been among the most popular and well-studied alternatives to Einstein's General Relativity. These theories of gravity contain an extra scalar degree of freedom that allows them to rectify some of the limitations of General Relativity but also fail some of the cornerstone tests of gravity that General Relativity passes with flying colors. Because of these conflicting features, it becomes necessary to investigate if scalar-tensor theories can pass current tests of gravity while still allowing for possible deviations from General Relativity in regimes that are not as highly constrained. In this thesis, we present the first self-consistent study of scalar-tensor theories in which we study the effects and constraints from Solar System observations, cosmological evolution of the universe, and the precise timing of binary pulsar systems. We constrain the free parameters of a certain class of massless-scalar-tensor theories first through cosmology and Solar System tests, in which we investigate the consistency between cosmological evolution scenarios and current Solar System observations. We then study strong field tests involving binary pulsar systems and investigate the various constraints that can be placed from measurements of the Keplerian and post-Keplerian parameters that determine the orbits.