Are time-domain self-force calculations contaminated by Jost solutions?

The calculation of the self force in the modeling of the gravitational-wave emission from extreme-mass-ratio binaries is a challenging task. Here we address the question of the possible emergence of a persistent spurious solution in time-domain schemes, referred to as a Jost junk solution in the literature, that may contaminate self-force calculations. Previous studies suggested that Jost solutions are due to the use of zero initial data, which is inconsistent with the singular sources associated with the small object, described as a point mass. However, in this work we show that the specific origin is an inconsistency in the translation of the singular sources into jump conditions. More importantly, we identify the correct implementation of the sources at late times as the sufficient condition guaranteeing the absence of Jost junk solutions.

Figure 1

Jost solution built by subtracting solutions to system (20) in approaches (I) and (II) for the jump implementation (cf. text) and using trivial ID in both cases.

Figure 2

Radial and time components of the self force as a function of time, with (“On”) and without (“Off”) time switch on of the sources ($r_p=6M$). Note that the Off case does not even allow the recovery of the second significant digit in ${\Phi }_r=1.677\times {10}^{-4}$, ${\Phi }_t=3.609\times {10}^{-4}$ (see e.g. 11).