Conveners
The Radiation Strikes Back: Nonlinear Effects in Binary Dynamics at Fifth Post-Newtonian Order
- Massimiliano Riva
Description
By fifth post-Newtonian order, a binary feels the nonlinear structure of its own radiation. The emitted waves scatter off the binary and off each other before being reabsorbed, introducing new time nonlocality into the effective action. Using the in-in worldline effective field theory, I will present the remaining far-zone effects (failed tails, memories and radiation reaction squared), which complete the 5PN relative dynamics and its scattering observables. Once all contributions are included, the disagreement between earlier EFT computations and post-Minkowskian results disappears. The memory’s nonlocality turns out to be harmless: it enters the action as a total derivative and drops out of the in-in equations of motion. It resurfaces, however, in memory-like terms once a conservative sector is isolated with Feynman’s prescription. I will discuss how to consistently extract a local conservative contribution to the 5PN Hamiltonian, which fixes the two remaining unknown EOB coefficients. Finally, I will compare different local prescriptions and ask what “conservative” really means for a radiating binary.