Asymptotic rate bounds for binary codes

What is the largest asymptotic rate of binary codes with relative distance 0<δ<1/2? The classical McEliece–Rodemich–Rumsey–Welch bound is the upper-bound baseline; related spherical-code questions use inner-product parameter 0<s<1.

Why it matters and what counts as progress

Why it matters: Improving rate bounds narrows the possible density of error-correcting codes beyond longstanding linear-programming baselines.

What counts as progress: Improve the rate upper bound at fixed δ, obtain larger code constructions, or strengthen the corresponding spherical linear-programming bounds.

How the problem developed

  1. 1977 · Upper bound [1]

    McEliece, Rodemich, Rumsey and Welch Introduced the linear-programming MRRW upper bound for the asymptotic rate of binary codes at fixed relative distance.

  2. 1 Aug 2026 · Reported claim [2][3]

    OpenAI Astra Reported an exponentially improved upper bound on maximum binary-code size at every prescribed relative distance 0<δ<1/2, strictly below the optimized MRRW bound.

AI contribution

Sources

  1. McEliece et al., New Upper Bounds on the Rate of a Code via the Delsarte-MacWilliams Inequalities
  2. OpenAI, Ten Advances in Mathematics, Chapter 2
  3. OpenAI, Ten Advances in Mathematics release and attribution
  4. OpenAI, code-bound formalization manifest
  5. OpenAI, binary-code comparator statement
  6. OpenAI, spherical-code comparator statement
  7. Sienicki and coauthors, Chapter 2 human review
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