gamma_onsager
plain-language theorem explainer
The Onsager susceptibility exponent gamma for the two-dimensional Ising model equals exactly 7/4. Researchers checking scaling relations or comparing lattice solutions to Recognition Science predictions cite this rational value. The declaration is a direct constant assignment drawn from the 1944 exact solution.
Claim. The critical exponent for magnetic susceptibility in the two-dimensional Ising model is given by $7/4$.
background
The module treats the two-dimensional Ising model, which Onsager solved exactly in 1944. Its critical exponents are the rationals nu = 1, eta = 1/4, beta = 1/8, gamma = 7/4, alpha = 0 (log divergence), and delta = 15. This definition supplies the gamma value that enters the scaling identities and the comparison with the Recognition Science leading-order formula nu_0 = phi^{-1}, which fails to recover the D = 2 result.
proof idea
The declaration is a direct definition that assigns the constant 7/4.
why it matters
The value is used by fisher_onsager to verify gamma = nu (2 - eta), by rushbrooke_onsager to confirm alpha + 2 beta + gamma = 2, by widom_onsager to confirm gamma = beta (delta - 1), and inside the Ising2DCert structure that records the 0.38 gap between nu_Onsager and 1/phi. It therefore sharpens the module's diagnostic that the Recognition Science forcing chain selects D = 3 rather than reproducing D = 2 exponents.
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