Spinning gravitating objects in the effective field theory in the post-Newtonian scheme

TL;DR

This paper develops an effective field theory framework for spinning gravitating objects in the post-Newtonian scheme, enabling precise calculations of spin effects in binary inspirals up to third order in the post-Newtonian expansion.

Contribution

It introduces a novel formulation for spinning objects in the effective field theory approach, including gauge choices and spin couplings, up to next-to-leading order in spin and post-Newtonian order.

Findings

Derived spin-dependent potentials up to third post-Newtonian order.

Obtained the next-to-leading order spin-squared potential and Hamiltonian.

Simplified calculations using nonrelativistic gravitational field decomposition.

Abstract

We introduce a formulation for spinning gravitating objects in the effective field theory in the post-Newtonian scheme in the context of the binary inspiral problem. We aim at an effective action, where all field modes below the orbital scale are integrated out. We spell out the relevant degrees of freedom, in particular the rotational ones, and the associated symmetries. Building on these symmetries, we introduce the minimal coupling part of the point particle action in terms of gauge rotational variables, and construct the spin-induced nonminimal couplings, where we obtain the leading order couplings to all orders in spin. We specify the gauge for the rotational variables, where the unphysical degrees of freedom are eliminated already from the Feynman rules, and all the orbital field modes are integrated out. The equations of motion of the spin can be directly obtained via a proper variation of the action, and Hamiltonians may be straightforwardly derived. We implement this effective field theory for spin to derive all spin dependent potentials up to next-to-leading order to quadratic level in spin, namely up to the third post-Newtonian order for rapidly rotating compact objects. In particular, the proper next-to-leading order spin-squared potential and Hamiltonian for generic compact objects are also derived. For the implementations we use the nonrelativistic gravitational field decomposition, which is found here to eliminate higher-loop Feynman diagrams also in spin dependent sectors, and facilitates derivations. This formulation for spin is thus ideal for treatment of higher order spin dependent sectors.