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2405.12737

Hyperuniformity of Random Measures on Euclidean and Hyperbolic Spaces

Michael Björklund, Mattias Byléhn

incompletemedium confidence
Category
Not specified
Journal tier
Specialist/Solid
Processed
Sep 28, 2025, 12:56 AM

Audit review

The candidate solution correctly proves the three asymptotic lower bounds (A)–(C) for the number variance on H^n by expressing NV as the L^2-mass of the spherical transform of ball windows and using standard Harish–Chandra asymptotics for spherical functions (principal and complementary series), including the σ=0 endpoint. This matches the core technical content of the paper’s approach: the paper derives an identity for χ̂_{B_R}(λ)=b_n sinh(R)^n ω^{(n+2)}_λ(R) and uses bounds/averages of |ω^{(n+2)}_λ(ar)|^2 to show (i) limsup_R NV/Vol(B_R)>0 when the principal diffraction is non-trivial and (ii) stronger growth when the complementary diffraction is present, with an R^2 factor at the endpoint λ=0 (Theorem 8.1 ⇒ Theorem 1.4) . However, as stated, Theorem 1.4 in the paper omits a necessary non-degeneracy assumption: for the degenerate invariant law that is almost surely a fixed multiple of the invariant volume, both diffraction measures vanish and NV≡0, contradicting limsup_R NV/Vol(B_R)>0; the proof step “Since |c_{n+2}(λ)|^2>0… the right-hand side is positive” implicitly assumes η̂^{(p)}_µ≠0 (or η̂^{(c)}_µ≠0) . The candidate explicitly flags this and restricts conclusions to non-degenerate invariant laws, so the model’s solution is correct under the standard, intended non-degeneracy assumption, while the paper’s theorem statement is incomplete on this point.

Referee report (LaTeX)

\textbf{Recommendation:} major revisions

\textbf{Journal Tier:} specialist/solid

\textbf{Justification:}

The paper develops a clear and useful hyperbolic analogue of lower bounds for number variance, introducing a principled spectral framework and proving sharp growth results linked to principal vs. complementary diffraction. The analysis is careful and uses appropriate harmonic-analytic tools (spherical transform, c-function asymptotics, Plancherel). However, the main hyperbolic theorem (Theorem 1.4) is stated without an explicit non-degeneracy assumption, leading to a formal counterexample (deterministic invariant measure with zero variance). This can be corrected by adding the intended hypothesis (nontrivial covariance/diffraction). With that amendment and a brief remark clarifying the endpoint handling at λ=0, the paper would be solid.