Anthropic Credits Claude Fable 5.2 for Black Hole Physics Result

Anthropic credited Claude Fable 5.2 with resolving a theoretical question about whether a black-hole-related phase transition remains first order under weak coupling. The calculation concerns a theoretical link between gravity and quantum theory, not observations of black holes in space.

An internal Claude research model produced the calculation, but its version was not identified. The quartic coefficient is b = −1.48 × 10⁻³ λ².

A 2003 study had outlined two possible patterns: one first-order transition or two continuous transitions. The new calculation addresses that question in a weak-coupling setting. A physicist checked several known special cases, and a separate Claude computation using another method reached the same result.

Anthropic also credited Fable 5.2 with a separate result in conformal field theory. The separate conformal-field-theory result has an exact bound of about 9.1266, while the prior best slope was bounded between 8.503 and 12. Public Claude Opus 5.5 later reached the same result, and a physicist checked every main result.

Anthropic’s Nov. 9 announcement listed Fable 5.2 as available across its platforms, with API prices of $8 per million input tokens and $40 per million output tokens. Both physics papers are version-one preprints dated Nov. 7.