A Possible Advanced Positron Signal in AMS-02 Measurements

Abstract

AMS-02 measurements show a striking separation between the characteristic energy scales of cosmic-ray electrons and positrons: the electron spectrum peaks near the ordinary retarded cooling scale, while the positron spectrum exhibits a high-energy structure at hundreds of GeV. I ask whether this hierarchy can be interpreted without introducing a dedicated additional positron source, dark matter component, or fine-tuned source population. Motivated by the Dirac/Feynman-Stueckelberg viewpoint, I formulate an effective transport response in which the positron sector contains a retarded branch and an advanced-associated branch with reduced accumulated radiative exposure. Two minimal realizations, a one-zone response model and a local-source response model, are used to compare the AMS-02 electron and positron spectra. In the cleaner local-source realization, the high-energy positron structure is carried predominantly by the advanced-associated branch, with an order-one branch weight and a strongly reduced effective exposure. I also discuss consistency conditions showing that this interpretation cannot be reduced to a simple survival-suppression or ordinary decoherence model. The result should be read as a possible advanced-associated positron response interpretation of the AMS-02 spectral hierarchy, not as a full Galactic propagation fit or a proof of microscopic backward-in-time propagation.