Effective-One-Body Hamiltonian in Scalar-Tensor Gravity at the Third Post-Newtonian Order
摘要
We determine the general local-in-time effective-one-body (EOB) Hamiltonian for massless Scalar-Tensor (ST) theories at third post-Newtonian (PN) order. For this, we first derive the order-reduced Lagrangian starting from the harmonic coordinate Lagrangian at the third post-Newtonian (PN) order and then obtain its corresponding centre of mass ordinary Hamiltonian. We then map the ordinary Hamiltonian to an effective-one-body (EOB) Hamiltonian at 3PN to derive the EOB metric potentials for the instantaneous part of the dynamics. We also explore the relevance of the 3PN scalar-tensor corrections by studying the innermost stable circular orbit (ISCO).