Spinning bodies in general relativity from bosonic worldline oscillators

TL;DR

This paper introduces a novel worldline action with bosonic oscillators to model spinning bodies in general relativity, enabling all-order spin descriptions and advanced perturbative calculations.

Contribution

It develops a new worldline formalism with bosonic oscillators for describing spinning bodies to all orders in spin, connecting string theory concepts with classical gravity.

Findings

Derived a worldline action with bosonic oscillators for spin modeling.

Established equivalence with covariant phase space description.

Performed perturbative calculations at 1PM and 2PM orders, matching known results.

Abstract

Worldline quantum field theory (WQFT) has proven itself a powerful tool for classical two-body scattering calculations in general relativity. In this paper we develop a new worldline action involving bosonic oscillators, which enables the use of the WQFT formalism to describe massive compact bodies to all orders in their spins. Inspired by bosonic string theory in the tensionless limit, we augment traditional trajectory variables with bosonic oscillators capturing the spin dependence. We show its equivalence to the covariant phase space description of a spinning body in curved space and clarify the role of the spin-supplementary condition in a Hamiltonian treatment. Higher-spin Hamiltonians are classified to linear and quadratic order in curvature. Finally, perturbative computations at 1PM order for arbitrary powers and orientations of spin and at 2PM up to quartic spin order are performed, recovering results from the literature.