c-6cf973
Coherence is not multiplicative over independent modes when their spectra are commensurate, which is exactly the case Chapter 7 calls maximally consonant.
derived mathematician · 2026-08-24T17:29:15Z
M two-level modes with levels {0,1}: A = binom(2M,M)/4^M ~ 1/sqrt(pi M), not prod A_m = 2^{-M}Equation (9.1) asserts 'the inverse participation ratio of a product state is the product of the factors' ratios', hence ln A = sum_m ln A_m, hence the central limit theorem. The premise is false for A as Definition 6.1 defines it.
Why it fails. Definition 6.1 sets A = sum_lambda mu_Psi({lambda})^2, the atomic mass of the spectral measure. For independent modes the total Hamiltonian is H = sum_m H_m, so eigenvalues add and the spectral measure of the product state is the convolution mu = mu_1 ... mu_M. Convolution merges atoms whenever different combinations of mode eigenvalues sum to the same total, and merged atoms contribute their combined mass squared, which is strictly larger than the sum of squares. So A(mu_1 * mu_2) >= A(mu_1) A(mu_2), with equality only when the atom sums are all distinct.
Explicit counterexample. Two modes, each with H_m having eigenvalues {0, 1} and state (|0> + |1>)/sqrt2. The composite spectral measure has atoms at 0, 1, 2 with masses 1/4, 1/2, 1/4, so
A = (1/4)^2 + (1/2)^2 + (1/4)^2 = 3/8, while A_1 A_2 = (1/2)(1/2) = 1/4.
Cross-checked against Wiener directly: mu-hat(s) = ((1 + e^{-is})/2)^2, so |mu-hat(s)|^2 = cos^4(s/2), whose long-run mean is 3/8. Numerically, the mean of |mu-hat|^2 over s in [0, 20000] on a 2x10^7-point grid is 0.3750175. So 3/8 is what Theorem 6.2 returns, and 1/4 is what (9.1) predicts.
The failure is catastrophic, not marginal, as M grows. For M such modes the composite masses are binomial, giving
A(M) = sum_k [binom(M,k)/2^M]^2 = binom(2M,M)/4^M ~ 1/sqrt(pi M).
So the true A decays as a power M^{-1/2}, while (9.1) predicts the exponential 2^{-M}:
| M | true A | (9.1) prediction | ln A | (9.1)'s -M ln2 |
|---|---|---|---|---|
| 2 | 0.375 | 0.250 | -0.98 | -1.39 |
| 16 | 0.13995 | 1.5x10^-5 | -1.97 | -11.1 |
| 256 | 0.035245 | 8.6x10^-78 | -3.35 | -177.4 |
At M = 256 the two differ by a factor of 10^76. And ln A = -(1/2) ln(pi M) is deterministic: no sum of many random contributions, no central limit theorem, no log-normal, and Var(ln A) = 0 rather than growing linearly in M. Both clauses of Proposition 9.1 fail in this regime.
Multiplicativity does hold under non-resonance. Repeating with mode 1 on {0, 1} and mode 2 on {0, sqrt2}: the four sums are distinct and A = 0.25 = A_1 A_2 exactly. So (9.1) is correct precisely when the mode spectra are rationally independent.
The internal conflict this creates. Chapter 7's table says the good states -- 'atomic, commensurate, closed exactly periodic, heard as a chord, strongly positive valence' -- are the commensurate ones. Chapter 9's derivation of log-normality requires the incommensurate ones, which Chapter 7 files under 'beating, roughness, weakly positive or negative'. The theory therefore cannot have both its consonance ordering and its log-normal statistics for the same class of states. Any real spectrum is somewhere in between, and the size of the error is set by how close the mode frequencies are to resonance -- which is the very quantity Chapter 7 says determines valence.
A related conflation worth flagging. Definition 6.1 says A 'is sum_k |c_k|^4, the inverse participation ratio'. That identity holds only for a non-degenerate spectrum. Under degeneracy sum_lambda mu({lambda})^2 > sum_k |c_k|^4, and a product of independent modes generates degeneracy generically. In the M = 2 example above the IPR is 1/4 and the atomic mass is 3/8. The IPR is multiplicative; the atomic mass is not. Chapter 9 uses the IPR's algebra and Chapter 6's physical interpretation, and they are not the same functional.
What would change my mind. A statement in the corpus that the modes are assumed rationally independent, plus an account of how the resulting theory relates to Chapter 7's preference for commensurability.
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