Fast Radio Bursts

Fast radio bursts are millisecond-duration, extragalactic pulses of radio emission with dispersion measures indicating propagation through substantial columns of ionized gas, placing most sources at cosmological distances. Their all-sky rate of thousands per day and their apparent isotropy suggest a cosmological population, but their physical origin — despite the identification of repeating sources and associated host galaxies — remains debated. The observed dispersion measure distribution, which encodes the integrated electron column density along each line of sight, shows scatter beyond what is expected from a uniform intergalactic medium density, with some bursts exhibiting DM values inconsistent with their inferred redshifts under standard ΛCDM assumptions about the baryon fraction of the intergalactic medium. The host galaxy population spans a wide range of types and metallicities, and no single progenitor model reproduces all observed properties.

Successive Collision Theory addresses FRB dispersion measure anomalies through the inhomogeneous distribution of ionized baryons in the post-collision debris field. In SCT, the intergalactic medium is not a smooth, well-mixed plasma settling uniformly from primordial nucleosynthesis products; it is structured by the angular momentum gradients and collision geometry of the initial pocket collision. Baryons that formed in or survived the collision concentrated preferentially along the angular momentum strata of the debris field, producing the cosmic web with its filaments, walls, and voids. Void regions have lower baryon densities than filament and wall regions, meaning that FRB lines of sight that traverse different large-scale structure environments will accumulate different dispersion measures at the same redshift. The scatter in DM beyond the mean cosmological prediction is therefore a direct measure of the variance in the baryon distribution along lines of sight — physically sourced by the collision's angular momentum field rather than by stochastic density fluctuations.

The pre-existing compact object populations from the colliding pockets provide a natural FRB progenitor population within the SCT framework. Magnetars, rapidly rotating neutron stars, and other compact remnants that survived the thermalization epoch were incorporated into the post-collision debris with non-standard spin rates and magnetic field configurations set by their pre-collision history. The observed range of FRB properties — including the repeating versus apparently non-repeating division, the diverse host galaxy types, and the range of intrinsic luminosities — reflects the diversity of pre-existing compact object populations across the two colliding pockets and the range of debris environments in which they subsequently resided. SCT predicts that the FRB host galaxy metallicity distribution should include a low-metallicity tail extending below what standard ΛCDM stellar evolution predicts, reflecting the pre-collision stellar generation whose remnants produce the most energetic and earliest-forming FRB sources.