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Oliver Pitt

Publications and source records attributed to Oliver Pitt.

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Post-Newtonian Global Conservation Laws in the Presence of Sensitive Bodies

The parameterized post-Newtonian (PPN) approach is the state of the art formalism for performing theory independent tests of weak-field gravity, and for constraining possible deviations from Einstein's theory. Within this framework, global conservation laws are useful for the calculation of dynamics and for giving meaning to parameters. In this paper we extend the concept of semi-conservative and fully-conservative theories of gravity to include situations in which compact astrophysical bodies are modeled as masses that are sensitive to their local environment, as relevant for theories that violate the strong equivalence principle. We find that globally conserved quantities can still exist in the presence of such sensitivities, and find their explicit forms when they do. We identify new ways of writing the coefficients that enter into the PPN metric when a theory of gravity admits conserved quantities in the presence of a sensitive body, and demonstrate the applicability of our approach by comparing it to known results in scalar-tensor theories of gravity.

gr-qc

Constraining the Cosmological Evolution of Post-Newtonian Parameters with Gravitational Wave Signals from Compact Binary Inspirals

Gravitational waves from compact binary inspirals offer a new opportunity to constrain the cosmological time dependence of gravitational coupling parameters, due to the high precision of the observations themselves as well as the significant cosmological redshifts at which such systems exist. We calculate theory-independent equations of motion for compact objects in a binary system, implementing a new approach to sensitivities, and subsequently determine the gravitational wave signal that one should expect to measure from their inspiral. Expressions for the wave phase and amplitude are derived in terms of post-Newtonian gravitational coupling parameters, radiative flux parameters, and compact body sensitivities. These results complement recent attempts to gain theory-independent constraints on the time-evolution of gravitational coupling parameters from cosmological probes, and represent a new opportunity to constrain modified gravity with gravitational wave data.

gr-qc