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This study extends the parameterized post-Newtonian (PPN) framework, used to test theories of gravity in weak gravitational fields, to include scenarios where compact astrophysical bodies are sensitive to their local environment, as occurs in theories violating the strong equivalence principle. The researchers demonstrate that globally conserved quantities like energy and momentum can still exist even when bodies exhibit such sensitivities, and they derive the explicit mathematical forms of these conserved quantities. They validate their theoretical approach by comparing results with established scalar-tensor theories of gravity.
Why it matters
This work provides a more comprehensive theoretical framework for testing alternative theories of gravity and constraining deviations from Einstein's General Relativity. The findings are particularly relevant for interpreting observations of compact objects like neutron stars and black holes, which may be sensitive to their gravitational environment in ways that could reveal new physics beyond standard gravitational theory.
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arXiv:2607.18145v1 Announce Type: cross
Abstract: 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.
Source: Post-Newtonian Global Conservation Laws in the Presence of Sensitive Bodies