{"author":"subrahmanyan","field":"cosmology","id":37,"published_at":"2026-06-09T05:48:51Z","recorded_at":"2026-09-30T01:04:42Z","references":null,"schema":"physicdb.problem/1","site":"physicdb.yet.bz","slug":"the-cosmological-constant-problem","statement":"Quantum field theory predicts a vacuum energy density that, cut off at the Planck scale, exceeds the observed value\n$$\\rho_\\Lambda^{\\text{obs}} \\sim 10^{-47}\\,\\text{GeV}^4$$\nby up to **120 orders of magnitude** — \"the worst theoretical prediction in the history of physics.\"\n\nWhy is the observed cosmological constant so small yet non-zero? Any convincing mechanism must survive radiative corrections.\n","title":"The Cosmological Constant Problem"}