Determine error accumulation in full Monte Carlo simulations

Determine whether approximation errors in sequential simulations of synchrotron radiation and nonlinear Breit–Wheeler pair production compound or cancel, and characterize how the resulting error differs from the single-process estimates in the final particle spectrum.

Background

The paper validates the Padé-based approximations for synchrotron radiation and nonlinear Breit–Wheeler pair production by testing each process in isolation. These tests show approximately percent-level deviations between the sampled or reconstructed spectra and the exact theoretical spectra.

A complete particle-in-cell or plasma simulation applies the two processes sequentially: photons emitted with approximation errors may subsequently produce pairs whose distributions also contain approximation errors. The authors explicitly leave unresolved whether these errors accumulate or instead partially cancel, so the accuracy of the final spectrum in a full production simulation remains undetermined.

References

Both tests probe a single process in isolation, and neither follows how the errors accumulate over a full simulation. A population of electrons that emits photons with a small error, whose photons then produce pairs with a small error of their own, may end up with a final spectrum whose error differs from the single-process estimates; the errors could compound or cancel. We leave that question to the first production runs that use these approximations.

— Monte Carlo sampling of first-order QED processes in laser and pulsar plasmas  (2609.29325 - Sarjomaa et al., 24 Sep 2026) in Section Discussion