REVIEW 1 major objections 6 minor 42 references
Entropies of the Poisson distribution as functions of intensity: "normal" and "anomalous" behavior
T0 review · 1 major / 6 minor · reviewed 2026-08-12 · deepseek-v4-flash
Pith's one-line read Tsallis and Sharma–Mittal entropies of the Poisson distribution always increase with intensity λ, but two generalized Rényi entropies can decrease over intervals of λ—an 'anomalous' non-monotonicity.
desk verdict Solid, modest paper: the Tsallis/Sharma-Mittal monotonicity results are clean, the anomaly claim is plausible, but two advertised bounds in Theorem 4.1 have a wrong exponential factor and need correction. 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 load-bearing object is ψ(α,λ)=Σ_{i≥0} p_i(λ)^α=$e^{{-αλ}}$Σ_{i≥0} $λ^{{iα}}$/(i!)^α. Every one of the six entropies is a functional of ψ and its logarithmic derivative: H_R=(1/(1−α))log ψ, H_T=(ψ−1)/(1−α), H_GR(α,β)=(log ψ(α,·)−log ψ(β,·))/(β−α), H_SM=($ψ^{{(1−β)/(1−α)}}$−1)/(1−β), and H_GR(α,·)=−∂_α log ψ. Since ψ is increasing in λ for 0<α<1 and decreasing for α>1, the signs in the definitions force Shannon, Rényi, Tsallis, and Sharma–Mittal entropies to increase in λ. The anomalous cases come from the mixed derivative: ∂_λ H_GR(α,λ)=−∂_α∂_λ log ψ(α,λ), evaluated at λ=1 through ρ(α)=α((Σ_{i≥1} i/(i!)^α)/(Σ_{i≥0}1/(i!)^α)−1); when ρ increases in α, the generalized Rényi entropy initially falls as λ rises.
What would settle it
Compute ρ(α)=α((Σ_{i≥1} i/(i!)^α)/(Σ_{i≥0}1/(i!)^α)−1) and ρ′(α) for α=$10^{{-k}}$, k=3,...,12, using the series or high-precision quadrature, and check whether ρ′(α)>0 on an entire interval near 0. Proposition 5.4 predicts such an interval; if ρ′≤0 for all sufficiently small α, the claimed decreasing behavior of H_GR(α,λ) near λ=1 would not follow from the given argument. Conversely, isolating an α with ∂_λ H_GR(α,λ)|_{λ=1}<0 would confirm the anomaly directly.
Extended reading notes
Core claim
On the paper's own terms, the central result is a classification of 'normal' versus 'anomalous' behavior for six entropy families on Poisson probabilities p_i(λ)=$e^{{-λ}}$λ^i/i!. Proposition 5.1 (with earlier work) establishes that Shannon, Rényi, Tsallis, and Sharma–Mittal entropies are strictly increasing functions of λ for all admissible parameter values. Proposition 5.4 establishes the existence of an interval J⊂(0,1) near 0 such that for every α∈J, the generalized Rényi entropy H_GR(α,λ)=−∂_α log ψ(α,λ) is decreasing in λ in a neighborhood of λ=1, so monotonicity fails even though ρ(α)=∂_λ log ψ|_{λ=1} is positive on (0,1). Proposition 5.8 transfers this non-monotonicity to the two-parameter entropy H_GR(α,β,λ) for β near such an α. The same section reports numerical observations of non-monotonicity for large α. Theorems 3.4 and 4.1 give the λ→∞ asymptotics and bounds: Shannon, Rényi, and both generalized Rényi entropies diverge logarithmically; Tsallis entropy grows like a power for α∈(0,1) and converges to 1/(α−1) for α>1; Sharma–Mittal entropy does the same with β in place of α.
Load-bearing premise
Proposition 5.4 assumes that a positive continuously differentiable function on (0,1) which tends to 0 at 0 and equals 0 at 1 must be increasing on some interval near 0; continuity and endpoint limits alone do not force this, and the paper supplies no further analytic information about ρ(α).
Editorial extensions
If this is right
- For a Poisson count model, the Tsallis and Sharma–Mittal entropies can be used as uncertainty measures that are guaranteed to grow with the rate λ, just as Shannon and Rényi entropies do.
- The one-parameter generalized Rényi entropy is not a universally reliable uncertainty measure: for α in a small interval near 0, increasing λ can lower the entropy over an interval starting at λ=1.
- For the two-parameter generalized Rényi entropy, any parameter pair close to an anomalous α inherits the decrease, so the phenomenon is not isolated to a single parameter choice.
- The asymptotic formulas give practical approximations: for large λ, Shannon, Rényi, and generalized Rényi entropies grow like (1/2)log(2πλ) plus parameter-dependent constants, while Tsallis (0<α<1) and Sharma–Mittal (0<β<1) grow as power laws.
- Two-sided estimates, e.g. for Shannon entropy L(λ) ≤ H_SH(λ) ≤ U_SH(λ), control the entropies uniformly for λ>1 and agree with the leading asymptotic term.
Reading between the lines
- The derivative identities used here—expressing each entropy through ψ and log ψ—are general; for any discrete distribution where ψ(α,λ) can be controlled, the same argument would classify monotonicity, so the Poisson results are likely a template rather than an isolated example.
- The large-α anomaly is presented numerically only; proving it analytically, for example by showing that the oscillating derivative ∂_λ H_GR(α,λ) crosses zero for every sufficiently large α, remains an open extension the paper does not attempt.
- In Poisson applications, the decreasing interval near λ=1 for small α means that a generalized Rényi-based score can fall when more events are observed, so practitioners should check monotonicity for their parameter range before using H_GR as an uncertainty measure.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper studies six entropy functionals—Shannon, Rényi, Tsallis, Sharma–Mittal, and two generalized Rényi entropies—for the Poisson distribution with intensity λ. It expresses all of them through the function ψ(α,λ)=Σ_i p_i(λ)^α, derives explicit formulas, asymptotic expansions as λ→∞, upper and lower bounds, and monotonicity results in λ. The main claims are that Shannon, Rényi, Tsallis, and Sharma–Mittal entropies are strictly increasing in λ for all admissible parameters, while the generalized Rényi entropies can be non-monotone for α near 0 (proved) and for large α (presented as numerical evidence), with the two-parameter version inheriting this non-monotonicity locally.
Significance. If correct, the monotonicity and anomaly results constitute a rigorous, parameter-free characterization of entropy behavior for Poisson count data, with practical cautionary value for researchers using generalized Rényi entropies as uncertainty measures. The ψ-based proof strategy is clean and yields explicit asymptotic constants; the main monotonicity theorems are correct, the α-near-0 anomaly proof is valid although terse, and the large-α anomaly is appropriately labeled numerical. The paper also provides useful explicit bounds, but the bound theorem contains a false statement for the Tsallis and Sharma–Mittal entropies in the α,β>1 regime; this does not undermine the monotonicity theorems but must be corrected before acceptance.
major comments (1)
- [Theorem 4.1, items 4–5 (proof on p. 10; eqs. (2.13), (3.14)–(3.15), (4.6))] For α>1 and β>1, the stated replacements are false. Combining (4.6) with (2.13) gives H_T(α,λ) ≥ 1/(α−1)[1−(2πλ)^{−(α−1)/2} e^{(α−1)h(λ)}], not the factor e^{−h(λ)} claimed in item 4; the analogous factor for H_SM(α,β,λ) in item 5 is e^{(β−1)h(λ)}, not e^{−h(λ)}. The stated stronger bound is numerically violated: at α=2, λ=1, H_T(2,1)≈0.6915, while the claimed lower bound 1−(2π)^{−1/2}e^{−h(1)}≈0.6954. For 0<α<1 and 0<β<1 the claimed bounds are true but weaker than what follows from (4.6); the theorem should state the correct exponential factors for each parameter range.
minor comments (6)
- [Proposition 5.4, proof] The inference that ρ must be increasing on an interval near α=0 is terse; please spell out the argument: for δ>0, the mean value theorem gives c∈(0,δ) with ρ′(c)=ρ(δ)/δ>0, and continuity of ρ′ then yields an interval around c, which can be chosen inside an arbitrarily small neighborhood of 0.
- [Proposition 2.3, proof step 3] In the proof of the lower bound for H_GR(α,β,p), the displayed expression should be −log μ(p), not μ(p).
- [Remark 5.2] For α>1 the text says the entropy is bounded by/increases to 1/(1−α); this should read 1/(α−1).
- [Abstract and Remark 5.7] The anomalous behavior for large α is numerical evidence, not a theorem; please state explicitly in the abstract or introduction that the proved anomaly covers α near 0, while the large-α anomaly is observed numerically.
- [Lemma A.6, part 1] The initial restriction γ∈(α,1) is incompatible with the later uniform choice γ≥γ* when α>γ*; rephrase the proof to allow γ∈(0,1) and rely on the uniform argument at the end of the lemma.
- [Proposition 5.8, proof of item 1] The proof covers β>1>α and β>1=α; please state explicitly that the α>1≥β case follows by the symmetry H_GR(α,β,λ)=H_GR(β,α,λ).
Circularity Check
No significant circularity: the monotonicity and anomaly results are derived from published, parameter-free properties of ψ(α,λ), and the anomalous behavior is not fitted or defined into existence.
full rationale
The paper's central claims are not circular. The Tsallis and Sharma–Mittal monotonicity results follow algebraically from the monotonicity of ψ(α,λ) in λ, a result quoted from the authors' prior work [9, Theorem 2]. That prior result is published, parameter-free, has stated assumptions that do not include the target monotonicity of Tsallis or Sharma–Mittal entropies, and is not equivalent to the present claims, so the self-citation is legitimate independent support rather than circularity. The anomalous behavior of H_GR(α,λ) is derived from an explicit derivative identity, ∂_λ H_GR = −∂_α∂_λ log ψ, and the proof of Proposition 5.4, while terse, is mathematically valid: strict positivity of ρ(δ) together with ρ(0)=0 gives, via the mean value theorem, a point c with ρ′(c)>0, and continuity gives an interval on which ρ′>0; no fitted parameter or target quantity is smuggled in. The large-α anomalous behavior in Remark 5.7 is explicitly labeled numerical and is not presented as a theorem, so it cannot constitute a circular derivation. There is no self-definitional step, no fitted input renamed as a prediction, no uniqueness theorem imported from the authors, and no ansatz hidden in a citation. The apparent error in Theorem 4.1 items 4–5, where substituting (4.6) into (2.13) yields a different exponent than claimed, is a correctness issue, not a circularity issue, and does not affect the monotonicity or anomaly derivations.
Assumptions & free parameters
assumptions (4)
- standard math Stirling-type bounds for n! and Γ(x+1), used throughout Sections 3 and 4
- standard math Term-by-term differentiation and uniform convergence of the series defining ψ(α,λ)
- domain assumption Saddle-point approximation replacing the sum in ψ(α,λ) by an integral with controlled remainder
- ad hoc to paper The function ρ(α) is increasing on some interval near α=0
Cite this review
Pith. "Pith review of Entropies of the Poisson distribution as functions of intensity: "normal" and "anomalous" behavior." pith.science (2026). https://pith.science/paper/HIVGFUFE
@misc{pith2026241116913,
author = {Pith},
title = {Pith review of: Entropies of the Poisson distribution as functions of intensity: "normal" and "anomalous" behavior},
year = {2026},
howpublished = {\url{https://pith.science/paper/HIVGFUFE}},
note = {Machine review of arXiv:2411.16913}
}
abstract
The paper extends the analysis of the entropies of the Poisson distribution with parameter $\lambda$. It demonstrates that the Tsallis and Sharma-Mittal entropies exhibit monotonic behavior with respect to $\lambda$, whereas two generalized forms of the R\'enyi entropy may exhibit "anomalous" (non-monotonic) behavior. Additionally, we examine the asymptotic behavior of the entropies as $\lambda \to \infty$ and provide both lower and upper bounds for them.
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Works this paper leans on
-
[1]
J. Acz´ el and Z. Dar´ oczy.¨Uber varallgemeinerte quasilineare Mittelwerte, die mit Gewichts- funktionen gebildet sind. Publ. Math. Debrecen, 10:171–190, 1963
work page 1963
-
[2]
S. Aning and M. Przyby la-Kasperek. Comparative study of twoing and entropy criterion for decision tree classification of dispersed data. Procedia Computer Science, 207:2434–2443, 2022
work page 2022
-
[3]
S. Arimoto. Information-theoretical considerations on estimation problems. Information and Control, 19:181–194, 1971
work page 1971
-
[4]
P. Barbiero, G. Ciravegna, F. Giannini, P. Li´ o, M. Gori, and S. Melacci. Entropy-based logic explanations of neural networks. Proceedings of the AAAI Conference on Artificial Intelligence, 36(6):6046–6054, 2022
work page 2022
-
[5]
A. Basit and Z. Iqbal. Recent advances in entropy: A new class of generalized entropy. Journal of Multidisciplinary Engineering Science and Technology (JMEST) , 7(11), 2020
work page 2020
- [6]
-
[7]
M. Belis and S. Guiasu. A quantitative-qualitative measure of information in cybernetic systems (corresp.). IEEE Transactions on Information Theory , 14(4):593–594, 1968
work page 1968
-
[8]
J. Boersma. Solution to problem 87-6* : The entropy of a Poisson distribution. SIAM Review, 30(2):314–317, 1988
work page 1988
Show all 42 references
-
[9]
Braiman, A
V. Braiman, A. Malyarenko, Y. Mishura, and Y. A. Rudyk. Properties of Shannon and R´ enyi entropies of the Poisson distribution as the functions of intensity parameter. Non- linear Anal. Model. Control , 29(4):802–815, 2024
2024
-
[10]
Buryak and Y
F. Buryak and Y. Mishura. Convexity and robustness of the R´ enyi entropy. Mod. Stoch. Theory Appl., 8(3):387–412, 2021
2021
-
[11]
T. M. Cover and J. A. Thomas. Elements of Information Theory . Wiley, Hoboken NJ, 2006
2006
-
[12]
S. Dey, S. S. Maiti, and M. Ahmad. Comparison of different entropy measures. Pakistan J. Statist. , 32(2):97–108, 2016
2016
-
[13]
E. D. Fagerholm, Z. Dezhina, R. J. Moran, F. E. Turkheimer, and R. Leech. A primer on entropy in neuroscience. Neuroscience & Biobehavioral Reviews, 146:105070, 2023
2023
-
[14]
Giunta, G
N. Giunta, G. Orlando, A. Carleo, and J. M. Ricci. Exploring entropy-based portfolio strategies: Empirical analysis and cryptocurrency impact. Risks, 12(5):78, 2024. 28
2024
-
[15]
Havrda and F
J. Havrda and F. Charv´ at. Quantification method of classification processes. Concept of structural a-entropy. Kybernetika (Prague), 3:30–35, 1967
1967
-
[16]
J. N. Kapur. Generalised entropy of order α and type β. Math. Seminar , 4:78–94, 1967
1967
-
[17]
J. N. Kapur. Some new nonadditive measures of entropy. Boll. Un. Mat. Ital. B (7) , 2(2):253–266, 1988
1988
-
[18]
Mahdy and D
M. Mahdy and D. S. Eltelbany. Application of entropy measures to a failure times of electrical components models. Pak. J. Stat. Oper. Res. , 13(4):909–930, 2017
2017
-
[19]
Majumdar and A
S. Majumdar and A. Sood. Statistical properties of entropy-consuming fluctuations in jammed states of laponite suspensions: fluctuation relations and generalized gumbel distri- bution. Physical Review E—Statistical, Nonlinear, and Soft Matter Physics , 85(4):041404, 2012
2012
-
[20]
Malyarenko, Y
A. Malyarenko, Y. Mishura, K. Ralchenko, and Y. A. Rudyk. Properties of various en- tropies of Gaussian distribution and comparison of entropies of fractional processes.Axioms, 12(11):1026, 2023
2023
-
[21]
Maszczyk and W
T. Maszczyk and W. Duch. Comparison of Shannon, R´ enyi and Tsallis entropy used in de- cision trees. In Artificial Intelligence and Soft Computing–ICAISC 2008: 9th International Conference Zakopane, Poland, June 22-26, 2008 Proceedings 9 , pages 643–651. Springer, 2008
2008
-
[22]
Mishura, K
Y. Mishura, K. Ralchenko, P. Zelenko, and V. Zubchenko. Properties of the entropic risk measure EVaR in relation to selected distributions. Modern Stochastics: Theory and Applications, pages 1–22, 2024
2024
-
[23]
M. A. Nielsen and I. L. Chuang. Quantum computation and quantum information . Cam- bridge University Press, Cambridge, 2000
2000
-
[24]
R. K. Pathria. Statistical Mechanics. Elsevier, 2011
2011
-
[25]
C.-F. Picard. Weighted probabilistic information measures. J. Combin. Inform. System Sci., 4(4):343–356, 1979
1979
-
[26]
P. N. Rathie. On a generalized entropy and a coding theorem. J. Appl. Probability, 7:124– 133, 1970
1970
-
[27]
A. R´ enyi. On measures of entropy and information. In Proc. 4th Berkeley Sympos. Math. Statist. and Prob., Vol. I , pages 547–561. Univ. California Press, Berkeley-Los Angeles, Calif., 1960
1960
-
[28]
T. N. Roach, J. Nulton, P. Sibani, F. Rohwer, and P. Salamon. Emergent structure in a stochastic model of ecological evolution. Ecological Modelling, 401:129–133, 2019
2019
-
[29]
Schneier
B. Schneier. Applied cryptography—protocols, algorithms and source code in C . Wiley Publishing, Inc., Indianapolis, IN, 2nd edition, 2015
2015
-
[30]
C. E. Shannon. A mathematical theory of communication. Bell System Tech. J., 27:379–423, 623–656, 1948
1948
-
[31]
B. D. Sharma and D. P. Mittal. New nonadditive measures of entropy for discrete probability distributions. J. Math. Sci. , 10:28–40, 1975
1975
-
[32]
B. D. Sharma and I. J. Taneja. Entropy of type ( α, β) and other generalized measures in information theory. Metrika, 22(4):205–215, 1975. 29
1975
-
[33]
B. D. Sharma and I. J. Taneja. Three generalized-additive measures of entropy. Elektron. Informationsverarb. Kybernet., 13(7-8):419–433, 1977
1977
-
[34]
I. J. Taneja. Generalized information measures and their applications, 2001. On-line book: www.mtm.ufsc.br/~taneja/book/book.html
2001
-
[35]
Trandafir, V
R. Trandafir, V. Preda, S. Demetriu, and I. Mierlu¸ s-Mazilu. Varma–Tsallis entropy: Prop- erties and applications. Review of the Air Force Academy , 16(2(37)):75–82, 2018
2018
-
[36]
C. Tsallis. Possible generalization of Boltzmann–Gibbs statistics. Journal of Statistical Physics, 52(1-2):479–487, 1988
1988
-
[37]
C. Tsallis. Introduction to nonextensive statistical mechanics: Approaching a complex world. Springer, 2009
2009
-
[38]
C. Tsallis. The nonadditive entropy Sq and its applications in physics and elsewhere: some remarks. Entropy, 13(10):1765–1804, 2011
2011
-
[39]
R. S. Varma. Generalizations of Renyi’s entropy of order α. J. Math. Sci. , 1:34–48, 1966
1966
-
[40]
S. Xu, L. B¨ ottcher, and T. Chou. Diversity in biology: definitions, quantification and models. Physical Biology, 17(3):031001, 2020
2020
-
[41]
R. Zhou, R. Cai, and G. Tong. Applications of entropy in finance: a review. Entropy, 15(11):4909–4931, 2013
2013
-
[42]
V. A. Zorich. Mathematical analysis. II . Universitext. Springer, Heidelberg, 2nd edition, 2016. 30
2016
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