REVIEW 2 major objections 4 minor 1 cited by
Zeros and exponential profiles of polynomials II: Examples
T0 review · 2 major / 4 minor · reviewed 2026-08-04 · deepseek-v4-flash
Pith's one-line read One exponential profile predicts zero limits of a dozen polynomial families
desk verdict A solid sequel that makes the exponential-profile method into a usable catalog, with a couple of genuinely new finite-free constructions. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The exponential profile g, defined as the limit of n^{-1} log a_{⌊αn⌋:n} over the degree index α, is the central object. The transfer theorem (Theorem 2.4) converts g into the limiting zero measure via the inverse-function relation tG(t) = (e^{−g′})^{-1}(t), where G is the Cauchy transform. For the free-probability constructions, Proposition 5.1 shows that if b_{k:n} has an exponential profile g̃, then the finite free convolution power has S-transform e^{g̃′(1+t)}; Laguerre's theorem is used to guarantee real-rootedness of the constructed polynomials.
What would settle it
Compute the roots for a moderately large n in a listed family, for example little q-Laguerre with q=e^{−λ/n} or Fubini polynomials, and compare the empirical zero measure with the predicted density; any systematic mismatch, or a single complex root in a family claimed to be real-rooted, would falsify that row of the table.
Extended reading notes
Core claim
The paper's central claim is that the exponential profile of a sequence of polynomials with nonpositive roots completely determines the limiting empirical zero distribution. Specifically, Theorem 2.4 (quoted from the authors' earlier work) says that if the k-th coefficient a_{k:n} satisfies log a_{⌊αn⌋:n}/n → g(α) for α in an interval, then the empirical zero measures converge, and the limiting Cauchy transform G satisfies that t↦tG(t) is the inverse of α↦e^{−g′(α)}. The paper's contribution is to verify the profile and nonpositive-root hypotheses for a wide table of classical families and to build new families from finite free convolution whose S-transforms are e^{g′(1+t)}, producing free m
Load-bearing premise
The whole table depends on the companion transfer theorem being valid and on each family genuinely having only nonpositive real roots; the paper often cites real-rootedness from other sources rather than proving it, so a single overlooked failure of real-rootedness would break that family's limit statement.
Editorial extensions
If this is right
- The limits compiled in Table 1 become corollaries of one transfer result: Touchard polynomials converge to a measure with moments (−k)^k/(k+1)!, Fubini to a Cauchy-type density, Eulerian to log-Cauchy, Laguerre to Marchenko–Pastur, and Hermite to the semicircle law.
- New polynomial families G_n(x;σ²/n) and P_n(x;b_n,c_n) give explicit finite-free-probability models whose zero limits are the free multiplicative normal and Poisson distributions.
- The inverse direction yields coefficient asymptotics for characteristic polynomials of sample covariance matrices: log a_{k:n} ≈ n g_M(k/n) with an explicit profile g_M.
- Little q-Laguerre polynomials with q=e^{−λ/n} connect to q-deformed GUE densities and recover Marchenko–Pastur as λ→0.
- Any real-rooted polynomial sequence with nonpositive roots and a computable profile can be plugged into the same recipe, so the method applies beyond the families listed.
Reading between the lines
- If the transfer is robust, the paper suggests a general 'profile-first' strategy: real-rootedness is the main obstruction, and many combinatorial families with known coefficient asymptotics should have zero limits that are free or classical laws waiting to be identified.
- The free multiplicative normal and Poisson constructions hint that finite free convolution powers can synthesize polynomials with prescribed free multiplicative limits; one might test whether fractional powers extend the semigroup and yield new infinite-divisibility results.
- The covariance-matrix coefficient asymptotics could be repeated for other random matrix ensembles with known limiting spectral measures, giving coefficient laws of large numbers via the same converse theorem.
- The q-Laguerre family interpolates between Marchenko–Pastur (λ→0) and q-deformed distributions; making that interpolation quantitative could yield new spectral statistics for q-Hermite ensembles.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper applies the exponential-profile method developed in the authors' companion paper [31] to a broad catalogue of polynomial families. For each family with nonpositive real roots and a coefficient profile, Theorem 2.4 converts the profile into the limiting empirical zero distribution via the inverse of a simple function. The catalogue covers Stirling, Touchard, Fubini, Eulerian, Narayana, hypergeometric, Laguerre, Hermite, Jacobi and little q-Laguerre polynomials. The paper also constructs new polynomial families whose zero distributions converge to the free multiplicative normal and Poisson distributions, treats differential-operator-generated families, and uses the converse theorem to obtain coefficient asymptotics for characteristic polynomials of sample covariance matrices. The resulting Table 1 is the main deliverable.
Significance. If the results hold, this is a useful unifying reference: a large collection of classical and free-probability examples are derived from one transfer principle, with explicit Cauchy transforms, densities, moments and logarithmic potentials. The new free multiplicative Hermite and Poisson polynomial constructions are of independent interest, and the inverse result in Section 6 gives a concrete new coefficient-limit theorem for random covariance matrices. The paper explicitly depends on the companion paper [31] for the central transfer theorem and on several imported real-rootedness results; that division of labour is normal for a sequel and not by itself a defect. The derivations I spot-checked (Touchard, Fubini, Eulerian, Laguerre/Marchenko–Pastur, Hermite/semicircle, and the hypergeometric rational profile) are algebraically consistent.
major comments (2)
- [§5.1.2, Lemma 5.9] The first proof for the case b≤-n is incorrect as written. For f(z)=(-b-z)^c, the only zero is z=-b, which is ≥ n > 0, not nonpositive. Hence f is not in the Laguerre–Pólya class with negative zeros and Laguerre's theorem (Theorem 5.6) cannot be applied. Remark 5.13 supplies a valid proof for b≠-n via the characteristic-polynomial identity, but the case b=-n is left unproved. Since Theorem 5.12 explicitly allows β=-1, this needs a fix, e.g. a continuity argument in b, or a separate treatment of b=-n.
- [§5.1.2, proof of Theorem 5.12] The proof applies Proposition 5.1 to Q_n with b_{k:n}=|(k+b_n)/n|^{c_n/n}. Proposition 5.1 requires Q_n to be real-rooted, but this is not verified and is in general false for non-integer exponents (cf. Remark 5.10). The conclusion can be obtained directly from the exponential profile of P_n, whose real-rootedness is the content of Lemma 5.9, together with [31, Lemma 6.1] for the S-transform. The gap is in the proof rather than in the statement, but it should be repaired.
minor comments (4)
- [§5.1, Proposition 5.1 and Remark 5.13] The displayed equations in these passages contain long repeated garbled strings ('⌟⟨⟨⟪rl⟫l⟩⟩⟪⌟⟪...') that make the definitions almost unreadable. This appears to be an encoding/compilation error and should be cleaned up before publication.
- [§4.7, text after Corollary 4.14] The statement 'One can check that t↦tG(t) is a solution to the quadratic equation' is slightly compressed; giving the explicit coefficient (σ^2 λ α^2 + (t+σ^2(1-λ))α - t = 0) in the prose would help the reader verify the inversion.
- [§4.8, Remark 4.16] The sentence 'the semicircle limiting distribution for Hen could have been derived directly ... using a trick discussed in Remark 2.6' is vague. A one-sentence indication of the shift (e.g. A = n^{1/2} sup |zeros|) would be useful.
- [§4.10, equation (47)] In the density formula, the notation p_{a|λ}(x) is used for a measure on [0,∞), while the coefficient profile was computed for P_n(-x). The reflection convention is clear from context, but a short sentence would prevent confusion.
Circularity Check
No significant circularity: the general profile-to-zero transfer is a companion-paper theorem independent of the examples; all applications use independent coefficient asymptotics and real-rootedness inputs.
full rationale
I walked the derivation chain. The key transfer results (Theorem 2.4, Theorem 2.5, and Lemma 6.1 of [31]) are cited from the authors' companion paper, but they are general, parameter-free statements about exponential profiles and Cauchy transforms; their statements do not mention any of the specific polynomial families or target measures, so using them is a normal division of labor rather than a circular reduction. Every application computes the exponential profile independently from classical asymptotic estimates (Stirling asymptotics, Bender's formulas, Riemann-sum limits) and then inverts alpha |-> exp(-g'(alpha)) exactly as Theorem 2.4 prescribes. The real-rootedness hypotheses are imported from external sources (Harper, Mez<0x0151>, [42], [52], Laguerre's theorem) or proved in the paper; none of these inputs equals the claimed zero-density conclusions. The new free-probability constructions are explicit coefficient choices whose limits are derived from the profile, not fitted to the stated limits. Section 6 applies the converse Theorem 2.5 to a known Marchenko-Pastur limit to obtain coefficient asymptotics, which is an inverse result, not a prediction from fitted parameters. The only real defect I found, Lemma 5.9's assertion that (-b-z)^c has nonpositive roots for b <= -n when the actual root is z = -b > 0, is a proof gap rather than circularity, and the paper supplies an alternative argument in Remark 5.13 covering the required cases. Thus no load-bearing step reduces to its own inputs.
Assumptions & free parameters
assumptions (5)
- standard math Theorem 2.4 and Theorem 2.5 from companion paper [31]: exponential profile of coefficients is equivalent to weak convergence of empirical zero distributions, with the Cauchy transform recovered from e^{-g'(alpha)}.
- domain assumption Real-rootedness (with nonpositive roots) of the polynomial families under consideration.
- standard math Laguerre's theorem: if f is in the Laguerre-Polya class and p has all real roots, then the coefficientwise transformed polynomial has all real roots.
- standard math Classical logarithmic asymptotics for Stirling numbers and factorials, e.g., Bender [7], Moser-Wyman [49].
- standard math Marchenko-Pastur theorem for sample covariance matrices, e.g., Bai-Silverstein [5, Theorem 3.6].
Cite this review
Pith. "Pith review of Zeros and exponential profiles of polynomials II: Examples." pith.science (2026). https://pith.science/paper/HXJI472L
@misc{pith2026250911248,
author = {Pith},
title = {Pith review of: Zeros and exponential profiles of polynomials II: Examples},
year = {2026},
howpublished = {\url{https://pith.science/paper/HXJI472L}},
note = {Machine review of arXiv:2509.11248}
}
abstract
In [Jalowy, Kabluchko, Marynych, arXiv:2504.11593v1, 2025], the authors discuss a user-friendly approach to determine the limiting empirical zero distribution of a sequence of real-rooted polynomials, as the degree goes to $\infty$. In this note, we aim to apply it to a vast range of examples of polynomials providing a unifying source for limiting empirical zero distributions. We cover Touchard, Fubini, Eulerian, Narayana and little $q$-Laguerre polynomials as well as hypergeometric polynomials including the classical Hermite, Laguerre and Jacobi polynomials. We construct polynomials whose empirical zero distributions converge to the free multiplicative normal and Poisson distributions. Furthermore, we study polynomials generated by some differential operators. As one inverse result, we derive coefficient asymptotics of the characteristic polynomial of random covariance matrices.
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Cited by 1 Pith paper
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