PyGRO: a Python Integrator for General Relativistic Orbits

Abstract

Advancement in recent years in the field of experimental gravitation has allowed to test the equivalence principle in regimes that were previously unexplored, allowing for unprecedented verifications of general relativity and also enabling tests of alternative theories of gravity. We introduce a new computational tool, PyGRO, with the aim of integrating numerically the geodesic equations for the trajectories of massive and massless test particles in any analytic four-dimensional space-time. The result is a modern, fast, open-source, highly customizable and user-friendly Python package to perform the numerical integration of the the geodesic equations. Combining symbolic and numerical calculations, PyGRO offers a variety of methods to obtain fully relativistic orbits with minimal intervention by the user, working in full generality with any user-given symbolic expression of the space-time metric tensor. We have tested PyGRO in an array of different scenarios, validating the methodology employed by successfully reproducing classical results from general relativity, which we report in this article.

15 pages, 14 figures, 1 table. Accepted for publication in Astronomy&Astrohysics. Code publicly available at https://github.com/rdellamonica/pygro

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