Reasoning:
- Rate chain: interstellar collisions with all CM-velocity components < 0.1c produce strangelets already at rest with respect to the galaxy — no stopping survival needed (complementary to the lunar bound’s loophole). R(100 GeV, Au) ≈ 1e-58 cm-3 s-1 x 10 Gyr → 1e-41 p-bar strangelets per cm3; 1e57 cm3 swept per protostar → P(star seeded) ≈ 1e16 p-bar; supernova statistics then force p-bar < 1e-19, i.e. p < 2e-8 over 2e11 collisions.
- Tightening: DDH’s worst-casing (Au-Au only, RHIC energies only) is physically backwards — production should peak at AGS energies (E^-3.4 rate scaling gives 4e4) and iron is nearly as good as gold (abundance factor 1e10) — so the honest bound is p < ~1e-21.
- The metastability escape: baryon-emission lifetimes are estimated at or below ~1e-7 s for the strangelets RHIC could plausibly make (lighter = less stable; heavier, longer-lived ones are much harder to produce), and 1e-7 s is near the upper end — but a strangelet with baryon-emission lifetime in the window (1e-7 s, ~Myr) would decay harmlessly in space yet stop and stabilize at RHIC. The authors judge this contrived but not as unphysical as the rapidity conspiracy; note decays that conserve baryon number are irrelevant (no evaporation). This is why no single empirical bound is airtight and the safety case rests on the conjunction of production, charge, and stability arguments.
Step 6 verdict
Verdict: approved (checked). Chain traced: interstellar collisions with all CM-velocity components < 0.1c produce strangelets at rest (no stopping-survival loophole - complementary to A-59); R ~ 1e-58 cm^-3 s^-1 x 10 Gyr (~3e17 s) ~ 3e-41 p-bar per cm^3, consistent with the quoted 1e-41; x 1e57 cm^3 swept per protostar ~ 1e16 p-bar per star; supernova statistics then force p-bar < 1e-19, i.e. p < 2e-8, tightening by the stated 4e4 (AGS-optimal energy) and 1e10 (iron abundance) factors. Hidden premises surfaced: (a) a seeded star’s conversion is luminous enough to appear in supernova-like statistics - grantable at these margins; (b) the strangelet survives the ~Myr to star formation - explicitly carved out inside the statement as the metastability escape, so the main defeater is internalized, and the honest weakening (“unless strangelets are metastable”) is exactly right. Anthropic selection is not an issue (distant conversions are observable). Valid.