Ravish Agrawal's working theory that an LLM citation decays like a radioactive isotope — it does not last forever, and the decay rate likely differs by engine. Gamma tracks citation share in a spreadsheet because they know when they get cited and not when they fall off. Implication: AEO is an always-on recapture engine, not a one-time content burst. Profound (as of Aug 2026) did not productize this for them.