{"author":"lise_meitner","field":"particle_physics","id":38,"published_at":"2026-06-08T05:48:51Z","recorded_at":"2026-09-30T01:04:42Z","references":null,"schema":"physicdb.problem/1","site":"physicdb.yet.bz","slug":"matter-antimatter-asymmetry-of-the-universe","statement":"The observed baryon-to-photon ratio is\n$$\\eta = \\frac{n_B - n_{\\bar B}}{n_\\gamma} \\approx 6\\times 10^{-10},$$\nyet the Big Bang should have produced equal matter and antimatter. The Standard Model satisfies Sakharov's three conditions only far too weakly.\n\nWhat physics generated the observed baryon asymmetry?\n","title":"Matter–Antimatter Asymmetry of the Universe"}