arXiv:2606.10007v1

On automorphic measures, Lyapunov exponents and instability of rational maps

Makienko Peter, Carlos Cabrera

math.DS37F1037F1537A25

Abstract

To construct obstructions to the stability of rational maps with non-summable critical points in their Julia sets, we introduce automorphic measures with complex eigenvalues for rational maps on the Riemann sphere. In particular, these measures extend the classical notions of quasi-invariant and conformal measures by allowing the respective Radon--Nikodym derivative to be complex-valued and proportional to a multiplicative cocycle. j(s,t)(R)=Rs(RR)t, j_{(s,t)}(R) = |R'|^{s} \left(\frac{|R'|}{R'}\right)^{t}, which plays the role of a generalized automorphy factor in the sense of group actions. The existence of such measures reveals a close connection between geometric and dynamical properties of rational maps. We show that the existence of certain automorphic measures, particularly unimodular measures and their associated vector fields, implies instability of the corresponding rational map. Specifically, for a weakly dissipative rational map admitting a (1,1)( -1, 1)-unimodular measure, there exists an integer q1q \ge 1 such that the map is qq-unstable. This result generalizes earlier instability criteria involving pseudoconformal measures and connects the presence of such measures to the failure of structural stability. Furthermore, we establish ergodic and combinatorial conditions ensuring the existence of unimodular measures or vector fields -- most notably, through bounded recurrence, bounded velocity of arguments, and relations with the Milnor--Thurston kneading theory. These criteria provide a unified framework linking automorphic measures, Lyapunov spectra, and the geometric deformation spaces of rational maps.

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Audited against arXiv v1

Not a correctness certificate. A “Correct” result may include yellow typos or minor formal corrections that do not affect substantive soundness. It means this audit found no unresolved substantive error under the stated criteria; it does not replace expert scrutiny or formal verification.

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Detailed mathematical audit

Generated August 18, 2026
01Statements4 reported findingsContains unsupported statements

The definitions and several elementary measure/cocycle observations are correct, but the main hyperbolicity and instability conclusions are not able to be verified. Essential compactness and deformation-space steps are asserted without hypotheses or proofs, and the construction of a global unimodular vector field from a positive-measure level set does not establish the required invariance.

Theorem 2Not able to verify

The characterization by negative pseudoconformal measures is not established

Pages 6 and 24–30 · Theorem 2, Lemmas 26–28, and Theorem 27 · arXiv:2606.10007v1

The converse direction uses Theorem 27(5), which is supposed to pass conformal measures on degenerating cycles of maps RiR_i to a pseudoconformal measure for the limit map RR. For negative ss, the proof introduces Radon–Nikodym factors φi\varphi_i and then says `by assumption' that they converge uniformly on compact subsets away from the critical values. No such assumption appears in the definition of a degenerated sequence, and weak convergence of the atomic cycle measures does not imply uniform convergence of those derivatives. Without this step, the conformal identity cannot be passed to the limit, so the deduction from non-hyperbolicity to existence of the measure remains unsupported.

Theorems 4 and 5Not able to verify

The q-stability and unimodular-measure instability chain lacks the hypotheses used in its proof

Pages 7–8 and 31–34 · Theorems 4 and 5, Lemma 29, Corollary 30, and Proposition 24 · arXiv:2606.10007v1

Lemma 29 assumes every critical orbit is infinite and that there are no critical relations. Corollary 30 drops those assumptions, and the proof of Theorem 4(2) invokes Lemma 29 for general hyperbolic maps, although hyperbolic maps may have periodic critical points and critical relations. Theorem 5 then uses Corollary 30 and Proposition 24, the latter again requiring no critical relations, without deriving those conditions from q-stability or from weak dissipativity. These are substantive missing cases, not notation changes, and the paper supplies no alternative deformation-space argument for them.

Theorem 11Not able to verify

The proof does not construct a globally valid unimodular vector field

Pages 11–12 and 35–38 · bounded-recurrence theorem · arXiv:2606.10007v1

From a Fourier coefficient of an eigenfunction, the proof obtains a phase τ\tau satisfying τN=λ\tau^N=\lambda and chooses a positive-measure level set Sj={τ=j}S_j=\{\tau=j\}. It then declares the restriction to SjS_j a unimodular vector field. The required equation, however, must hold almost everywhere for a measure whose support is dynamically compatible; the proof does not show that SjS_j is invariant or nonsingular under RR, so extending the restriction by zero need not satisfy the automorphy relation. The earlier analogous selection of a positive-measure level set has the same issue.

Basic automorphic-measure identitiesCorrect

The variation and cocycle calculations are correct where their hypotheses hold

Pages 2–10 and Section 2 · definitions, transfer identities, and Propositions 7–10 · arXiv:2606.10007v1

Taking variation of a unimodular automorphic measure yields the stated pseudoconformal measure, and its Radon–Nikodym derivative satisfies the displayed unit-vector cocycle. The transfer-operator inequalities and the construction from an already existing invariant line field are algebraically correct. These valid preliminary facts do not resolve the missing existence and deformation arguments above.

02Proofs4 reported findingsContains incorrect or incomplete proofs

Three central proof chains are incomplete: conformal identities are passed through degenerating maps using an unstated uniform convergence assumption; q-stability arguments apply lemmas outside their hypotheses; and positive-measure level sets are used without proving invariance. These gaps propagate to Theorems 2, 4, 5, and 11 and their instability corollaries.

Theorem 27(5)Incomplete as written

Weak convergence of cycle measures does not give uniform convergence of Radon–Nikodym factors

Pages 28–29 · degenerated-sequence case · arXiv:2606.10007v1

The definition of a degenerated sequence controls only the cycle multipliers and local uniform convergence of the rational maps away from poles. It gives no compact-uniform control of d(ρs,XiRi1)/dρs,Xid(\rho_{s,X_i}\circ R_i^{-1})/d\rho_{s,X_i} on the varying atomic supports. The asserted convergence of φi\varphi_i is therefore not an available assumption, and critical-point concentration can make negative powers singular. A repair needs explicit tightness away from critical values and a uniform-integrability argument strong enough to pass the weighted pullback identity.

Lemma 29, Corollary 30, and proof of Theorem 4Incomplete as written

The no-critical-relations hypothesis disappears at the point it is needed

Page 31 · deformation-space argument · arXiv:2606.10007v1

Lemma 29 states its dimension criterion only when every critical point has infinite orbit and no critical relations occur. Corollary 30 restates the criterion for `a rational map' without retaining either condition. The proof of Theorem 4(2) then applies it to arbitrary hyperbolic structurally stable maps. Since hyperbolicity does not exclude periodic critical points, the cited lemma cannot justify that step. The missing critical-relation cases must be analyzed separately or the theorem restricted.

Proof of Theorem 5Incomplete as written

The transfer-operator cancellation invokes an inapplicable proposition

Pages 32–34 · generalized Cauchy-transform argument · arXiv:2606.10007v1

The proof uses Proposition 24 to expand the Ruelle transform and then uses q-stability to select invariant Beltrami differentials forcing all critical-value coefficients to vanish. Proposition 24 assumes normalization and absence of critical relations, while Theorem 5 assumes neither. Corollary 30, used for the selection, inherits the unresolved hypothesis problem above. Consequently the eigenfunction relation needed for Lemma 31 and the contradiction with weak dissipativity has not been obtained in the full stated generality.

Proof of Theorem 11Incomplete as written

A positive-measure cocycle level set is not shown to support an automorphic measure

Pages 36–38 · essential-values and Fourier-coefficient argument · arXiv:2606.10007v1

Selecting SjS_j with positive measure only proves that one root value occurs frequently. To turn a phase on SjS_j into a vector field whose product with the pseudoconformal measure is automorphic, one must prove R1Sj=SjR^{-1}S_j=S_j modulo that measure or construct an invariant component carrying the same cocycle equation. Neither is done. The missing invariance cannot be supplied by merely restricting the vector field, because the automorphy identity compares values at xx and R(x)R(x).

03Novelty0 reported findingsNo non-novelty findings

No non-novelty findings.

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Paper
arXiv:2606.10007v1
Authors listed
Makienko Peter, Carlos Cabrera
Audit date
August 18, 2026
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