2025/11/20 by A. Placidi, Placidi, Andrea, Lorenzo Sebastiani +3
Physics and Astronomy · #FOS: Physical sciences #General Relativity and Quantum Cosmology (gr-qc) #High Energy Physics - Theory (hep-th) #Pulsars and Gravitational Waves Research #Quantum Chromodynamics and Particle Interactions #Relativity and Gravitational Theory
paper · pdf · doi:10.48550/arxiv.2511.16747
openalex publication_date 2025/11/20 · openalex created_date 2025/11/25 · openalex updated_date 2026/07/28
We derive the gauge-general expressions of the two gyro-gravitomagnetic functions entering the spin-orbit sector of the effective-one-body (EOB) Hamiltonian up to the fifth-and-half post-Newtonian (5.5PN) order. Our results include both local and nonlocal-in-time contributions, providing the most general analytical formulation of the linear-in-spin conservative dynamics within the EOB framework. These expressions are then employed to compute two gauge-invariant observables for quasi-circular orbits: the binding energy and the fractional periastron advance. We also use them to compare two spin-gauge choices: the well-known Damour-Jaranowski-Schäfer (\rm DJS) gauge, in which the gyro-gravitomagnetic functions are independent of the orbital angular momentum, and the alternative anti-\rm DJS (or \rm DJS) gauge, designed to reproduce in the test-mass limit the spin-orbit interaction of a spinning test particle in a Kerr background. For a circular, equal-mass, equal-spin binary, our analysis indicates that the \rm DJS gauge provides a slightly improved description of the inspiral dynamics, suggesting potential advantages for its use in future EOB waveform models.