REVIEW 3 major objections 3 minor 1 cited by
A characterization of uniqueness of purely atomic finite measures with central Cantor set range
T0 review · 3 major / 3 minor · reviewed 2026-08-27 · deepseek-v4-flash
Pith's one-line read The paper characterizes when a purely atomic finite measure is uniquely determined by its range: for central Cantor sets no canonical term may be twice its successor, and for symmetric Cantor sets the representation must be irreducible…
desk verdict A genuinely useful central Cantor characterization, with a symmetric-set extension that is conditional on an unproved and miscounted gap-order observation. 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 central object is the achievement set $E(x_n) = \{\sum_{n\in A} x_n : A \subseteq \mathbb{N}\}$ of a summable non-increasing sequence; the range of the measure is exactly this set. The main diagnostic used for central Cantor sets is the center of distances $C(E)$, the set of all $\alpha \geq 0$ such that from every point of $E$ there is another point of $E$ at distance $\alpha$. A known theorem characterizes when $C(E)$ is minimal for central Cantor sets in terms of three local ratio patterns, and that characterization is what forces $x_n = 2x_{n+1}$ in the non-unique case. For symmetric Cantor sets the proof mechanism is gap geometry: the longest dominating gap — a gap longer than every gap to its left — is principal, and the proof aligns any alternative representation against the canonical one by matching translated copies of remainder achievement sets, called pseudointervals, until the first block of terms coincides; an induction over the sequence of dominating gaps then forces all terms to coincide.
What would settle it
A concrete check: take a symmetric Cantor set satisfying irreducibility and $M_n \leq 2$ (for example multiplicities $M=(2,1,1,\ldots)$ with $\alpha_p$ chosen so that no $\alpha_p$ equals $(M_{p+1}+1)\alpha_{p+1}$), list the $E$-gaps of order at most $n$ in increasing order, and look for a gap shorter than $\alpha_n-R_n$ that is either the last such gap or is followed by a gap of a different length. One such example would refute the unproved Observation and break the supplied proof of the direction of Theorem 5 asserting that irreducibility with multiplicities at most two forces uniqueness.
Extended reading notes
Core claim
The central discovery is a necessary-and-sufficient criterion. A central Cantor set with left endpoint $0$, in its unique fast-convergent representation $(x_n)$, is the range of exactly one purely atomic finite measure if and only if $x_n \neq 2x_{n+1}$ for every $n$. If some $x_n = 2x_{n+1}$, the paper constructs an explicit different sequence with the same achievement set: the pair $(x_n,x_{n+1})$ is replaced by three copies of $x_{n+1}$. The converse is proved by passing through the center of distances: any alternative representation either forces a term to be repeated, which by the repeated-value lemma puts a multiple of that term into the center of distances and thereby produces the doubling, or makes the center of distances non-minimal, which by the known characterization also produces $x_n = 2x_{n+1}$. For symmetric Cantor sets the criterion is that the semi-fast representation $E(\alpha_n; M_n)$ be irreducible, meaning $\alpha_n \neq (M_{n+1}+1)\alpha_{n+1}$ for every $n$, and that every multiplicity satisfy $M_n \leq 2$; the harder direction is proved by aligning pseudointervals from the longest dominating gap outward and inducting over all dominating gaps.
Load-bearing premise
The load-bearing premise is the unproved Observation in Lemma 6, which says that in the ordered list of gaps of order at most $n$ every gap shorter than $\alpha_n-R_n$ is immediately followed by a gap of length exactly $\alpha_n-R_n$; if that adjacency pattern fails, the pseudointerval-alignment proof of the uniqueness direction of Theorem 5 collapses.
Editorial extensions
If this is right
- For central Cantor sets, uniqueness of the range is equivalent to the local test $x_n \neq 2x_{n+1}$ for every $n$; no other global condition is needed.
- Every symmetric Cantor range failing the criterion is explicitly non-unique: reducible values admit a split-and-merge substitution, and any multiplicity at least $3$ admits a replacement representation.
- Every uniquely achievable symmetric Cantor range has an irreducible semi-fast representation with no value occurring more than twice.
- The sufficient condition of Theorem 8 yields uniquely achievable Cantorval ranges beyond the standard two-term Cantorval, including some sequences whose topological type is unknown.
- In the Cantorval family generated by Theorem 9, the standard two-term Cantorval is the only uniquely achievable member; every other member contains a doubled term.
Reading between the lines
- The results point to a local-ratio dichotomy for all achievement sets: non-uniqueness may always come from a regrouping of terms into a doubled, tripled, or reducible pattern. If so, the paper's Problem 12 would have an affirmative answer, but that is an extrapolation, not proved here.
- The pseudointerval-matching argument in Lemma 6 is a rigidity mechanism that could transfer to other centrally symmetric or self-similar sets; a testable extension is to symmetric Cantor sets with non-uniform dissection ratios.
- The unproved Observation about gap ordering is computationally checkable for the Cantorval families generated in the paper; a failure there would not necessarily refute Theorem 5 but would require a different proof.
Signed reviews
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript studies unique achievability of achievement sets of summable positive non-increasing sequences, interpreted as ranges of purely atomic finite measures. The main results are: Theorem 4 characterizes uniquely achievable central Cantor sets by the condition x_n ≠ 2x_{n+1} for all n; Theorem 5 characterizes uniquely achievable symmetric Cantor sets as precisely those with an irreducible semi-fast representation (α_n; M_n) and M_n ≤ 2 for all n; and Theorem 8 gives a sufficient condition for unique achievability of a class of Cantorvals, yielding new examples beyond the Guthrie–Nymann Cantorval. The proof of Theorem 4 uses the Banakiewicz theorem on centers of distances, while Theorem 5 relies on a detailed geometric analysis of pseudointervals and a long Lemma 6. The paper closes with remarks and open problems on unique achievability of Cantorvals.
Significance. If correct, Theorem 4 is a clean complete characterization for central Cantor sets, and Theorem 5 is a substantial extension to the broader class of symmetric Cantor sets. Theorem 8 is a short, checkable argument that produces the first new uniquely achievable Cantorvals beyond the Guthrie–Nymann example. The center-of-distances argument in Theorem 4 is elegant, and the statement of Theorem 8 is falsifiable and clearly illustrated by the multigeometric examples. The main risk is in the proof of Theorem 5, which depends on Lemma 6 and on an induction over dominating gaps; several steps in that proof are not currently fully supported.
major comments (3)
- [Section 2, Lemma 6, 'Observation'] The Observation as stated cannot be correct. With M := ∏_{i=1}^n M_i, the list (L_j)_{j=1}^M cannot enumerate all E(y_i)-gaps of order at most n: for the central Cantor case M_i ≡ 1 and n = 2, there are three gaps of order at most 2 (one of order 1 and two of order 2), while M = 1. In general the number of such gaps is ∏_{i=1}^n(M_i+1) − 1. Moreover, the Observation is asserted without proof. It is used in two decisive places in the proof of (10), namely the case d ≤ s−2 and the induction step for the pseudointervals W_t, to conclude that the next pseudointerval gap has length exactly α_n − R_n. Until the Observation is corrected and proved, the alignment argument that establishes (10) is unsupported.
- [Section 2, proof of Theorem 5 (⇐)] The proof begins with the assertion 'Since E has infinitely many gaps, it has infinitely many dominating gaps.' This contradicts the definition of a dominating gap given in Section 1 (all E-gaps lying to the left are shorter). In a compact set, the lengths of gaps tend to 0 near the right endpoint, so there are only finitely many record highs from the left; for example, the ternary Cantor set E(1/3^n), which satisfies the hypotheses of Theorem 5, has a unique dominating gap under this definition. The induction over the sequence (n_i) therefore needs a different construction: presumably the indices should be chosen recursively as the longest dominating gap of each successive tail E∩[0,R_{n_i}]. This must be stated and proved before the induction is valid.
- [Section 2, proof of Lemma 6, Case 2] Several steps in Case 2 are deferred to 'an argument analogous to the proof of (10)' and 'in a manner analogous to the final part of the proof that (6) and (7) cannot hold simultaneously'. Since the proof of (10) itself is not yet established (see the comments on the Observation), and since the arguments rely on visual inspection of Figures 1–3, this part of the case analysis is not sufficiently self-contained. The authors should either give a complete proof of (10) and then spell out the analogous arguments for Case 2, or restructure the proof so that every alignment of pseudointervals is justified by an explicit combinatorial statement rather than by reference to figures.
minor comments (3)
- [Throughout] There are numerous typographical and OCR artifacts, for example 'PUREL Y A TOMIC' in the title, 'Gł¸ ab' in the references, and 'j∈s+1,...,s,' in Case 2 of Lemma 6. These should be cleaned up before publication.
- [Section 2, proof of Lemma 6] In the proof of (10), the sentence 'If min ˜P2 ∈ [min P^(2)_1, max P^(2)_1], then max ˜P2 ∈ P^(2)_2' does not address the case where min ˜P2 lies in the gap (max P^(2)_1, min P^(2)_2); this intermediate case appears to be excluded only implicitly, and the exclusion should be justified.
- [Section 3, Proposition 10] The proof that K ≠ {2n} forces the existence of m with m, m+1 ∉ K and m+2 ∈ K is stated in one sentence and deserves a short justification, since the preceding dichotomy only rules out consecutive elements of K and three consecutive non-elements of K.
Circularity Check
No significant circularity: the new uniqueness characterizations are proved from published external lemmas, explicit alternative representations, and independent gap-structure arguments, not from their own conclusions.
full rationale
Theorems 4, 5, and 8 do not reduce to their inputs. Theorem 4 is proved by combining Banakiewicz's published characterization of non-minimal centers of distances with an explicit multiplicity/sum argument for the minimal-center case; neither ingredient assumes the target uniqueness statement, and the conclusion x_{n-1}=2x_n in the minimal case follows from fast convergence plus Proposition 3 rather than from the statement being proved. The (⇐) direction of Theorem 5 is an induction whose engine, Lemma 6, is a geometric analysis of pseudointervals; while Lemma 6 relies on several same-circle citations (e.g., the Third Gap Lemma from [4]), those are published, parameter-free lemmas whose assumptions do not include unique achievability, so they count as genuine evidence rather than circular imports. The most serious concern in the manuscript is not circularity but an omitted proof: the unproved 'Observation' inside Lemma 6 (Section 2), which asserts a gap-alignment property for 'all E(y_i)-gaps of order at most n' and appears miscounted as written (M=∏M_i cannot be the number of such gaps even in the central case). That observation is load-bearing for the proof of (10), so if false or unproved it would endanger the 'if' direction of Theorem 5; however, it is asserted as a structural fact about the given semi-fast representation, not as a restatement of the theorem, so it does not make the derivation circular. Theorem 8 is self-contained: it identifies principal gaps of the given representation and matches them one-by-one to any alternative representation, with no fitted parameters or conclusions built into the assumptions. No self-definitional, fitted-input, or renaming pattern is present. Accordingly the circularity score is 0.
Assumptions & free parameters
assumptions (6)
- domain assumption Every central Cantor set with min 0 has a unique fast convergent representation (x_n).
- domain assumption Banakiewicz Theorem: the center of distances of a central Cantor set E(x_n) is non-minimal iff one of conditions (i)-(iii) holds.
- domain assumption Third Gap Lemma: every dominating gap is principal.
- domain assumption Proposition 3: if x_p = x_{p+1} = ... = x_{p+2j-2}, then j x_p ∈ C(E(x_n)).
- domain assumption Every symmetric Cantor set with left endpoint 0 equals E(α_k; N_k) for a semi-fast convergent sequence.
- ad hoc to paper The Observation in Lemma 6: among E(y_i)-gaps of order at most n in natural order, any gap shorter than α_n − R_n is not the last and the next gap has length exactly α_n − R_n.
Cite this review
Pith. "Pith review of A characterization of uniqueness of purely atomic finite measures with central Cantor set range." pith.science (2026). https://pith.science/paper/OYUE2FD3
@misc{pith2026260814395,
author = {Pith},
title = {Pith review of: A characterization of uniqueness of purely atomic finite measures with central Cantor set range},
year = {2026},
howpublished = {\url{https://pith.science/paper/OYUE2FD3}},
note = {Machine review of arXiv:2608.14395}
}
read the original abstract
We study purely atomic measures whose range is a central Cantor set and characterize those central Cantor sets that are the range of exactly one such measure. Next, we extend the characterization to the case of symmetric Cantor sets using a different method of proof. Finally, we make a few initial observations and remarks on recovering a measure whose range is a Cantorval.
Figures
Figures from the paper (1 more)
Forward citations
Cited by 1 Pith paper
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Maximal Center of Distances of Finite Ultrametric Spaces and Perfect Binary Trees
MCD-spaces (maximal center of distances) are exactly those with perfect binary representing trees, and two such spaces are isometric if and only if they have the same center of distances.
Reference graph
Works this paper leans on
- [1]
-
[2]
Banakiewicz,The center of distances of central Cantor sets, Results Math.78(2023), art
M. Banakiewicz,The center of distances of central Cantor sets, Results Math.78(2023), art. no. 234, https://doi.org/10.1007/s00025-023-02012-3
-
[3]
M. Banakiewicz, A. Bartoszewicz, M. Filipczak, F. Prus-Wiśniowski,Center of distances and central Cantor sets, Results Math.77(2022), art. no. 196, https://doi.org/10.1007/s00025-022-01725-1
-
[4]
A. Bartoszewicz, M. Filipczak, S. Gł¸ ab, F. Prus-Wiśniowski, J. Swaczyna,On generating regular Cantorvals connected with geometric Cantor sets, Chaos, Solitons and Fractals,114(2018), 468–473
work page 2018
-
[5]
A. Bartoszewicz, M. Filipczak, G. Horbaczewska, S. Lindner, F. Prus-Wiśniowski,On the operator of center of distances between the spaces of closed subsets of the real line, Topol. Methods Nonlinear Anal.63(2) (2024), 413–427
work page 2024
-
[6]
A. Bartoszewicz, M. Filipczak, F. Prus-Wiśniowski,Topological and algebraic aspects of subsums of series, Tradi- tional and present-day topics in real analysis, 345–366, Faculty of Mathematics and Computer Science. University of Łódź, Łódź, 2013
work page 2013
-
[7]
A. Bartoszewicz, M. Filipczak, F. Prus-Wiśniowski,Semi-fast convergent sequences andk-sums of central Cantor sets, Eur. J. Math.6(2020), 1523–1536
work page 2020
-
[8]
A. Bartoszewicz, M. Filipczak, E. Szymonik,Multigeometric sequences and Cantorvals, Cent. Eur. J. Math.12(7) (2014), 1000–1007
work page 2014
Show all 34 references
-
[9]
Bartoszewicz, S
A. Bartoszewicz, S. Gł¸ ab, J. Marchwicki,Recovering a purely atomic finite measure from its range, J. Math. Anal. Appl.467(2018), 825–841
2018
-
[10]
Bielas, S
W. Bielas, S. Plewik, M. Walczyńska,On the center of distances, Eur. J. Math.4(2018), 687–698
2018
-
[11]
Dovgoshey, O
O. Dovgoshey, O. Rovenska,Center of distances of ultrametric spaces generated by labeled trees, Mathematics 14(5) (2026), 865
2026
-
[12]
Dovgoshey, O
O. Dovgoshey, O. Rovenska,On the center of distances of finite ultrametric spaces, arXiv:2603.25850
-
[13]
Feng, D., Rao, H., Wu, J.,The net measure properties of symmetric Cantor sets and their applications, Progress in Natural Science7(2)(1997), 172–178
1997
- [14]
-
[15]
Gł¸ ab, J
S. Gł¸ ab, J. Marchwicki,Set of uniqueness for Cantorvals, Results Math.78(2023), art. no. 9, DOI:10.1007/s00025-022-01777-3
2023 doi
-
[16]
S. Głąb, J. Marchwicki,On arithmetic sums of Cantor sets: P-sums vs. achievement sets, to appear in: Riv. Math. Univ. Parma
-
[17]
Guthrie, J.E
J.A. Guthrie, J.E. Nymann,The topological structure of the set of subsums of an infinite series, Colloq. Math. 55(2) (1988), 323–327
1988
-
[18]
S. Głąb, F. Prus-Wiśniowski,Achievement sets — current results and open problems, Real Anal. Exchange Advance Publication (2026), 1–25, DOI: 10.14321/realanalexch.1766383782
2026 doi
-
[19]
Jones,Achievement sets of sequences, Am
R. Jones,Achievement sets of sequences, Am. Math. Mon.118(6) (2011), 508–521
2011
-
[20]
Kakeya,On the partial sums of an infinite series, Tôhoku Sc
S. Kakeya,On the partial sums of an infinite series, Tôhoku Sc. Rep.3(1914), 159–164
1914
-
[21]
Kakeya,On the set of partial sums of an infinite series, Proc
S. Kakeya,On the set of partial sums of an infinite series, Proc. Tokyo Math.-Phys. Soc., 2nd series,7(1914), 250–251,https://doi.org/10.11429/ptmps1907.7.14_250
1914 doi
-
[22]
et al.On the union of homogeneous symmetric Cantor set with its translations, Math
Kong, D., Li, W., Wang, Z. et al.On the union of homogeneous symmetric Cantor set with its translations, Math. Z.307, (2024), art. no. 35
2024
-
[23]
Kula,Center of distances and Bernstein sets, Real Anal
M. Kula,Center of distances and Bernstein sets, Real Anal. Exchange50(1) (2025) 207–212, DOI: 10.14321/re- alanalexch.1739330962
2025 doi
-
[24]
M. Kula, P. Nowakowski,Achievement sets of series inR 2, Results Math.79(2024), art. no. 221, https://doi.org/10.1007/s00025-024-02239-8
2024 doi
-
[25]
Exchange25(2) (1999/2000), 799–808
Lu S.,The Hausdorff dimension and measure of some Cantor sets, Real Anal. Exchange25(2) (1999/2000), 799–808
1999
-
[26]
Marchwicki, J
J. Marchwicki, J. Miska,On Kakeya conditions for achievement sets, Results Math.76(2021), art. no. 181
2021
-
[27]
Marchwicki, P
J. Marchwicki, P. Nowakowski, F. Prus-Wiśniowski,Algebraic sums of achievable sets involving Cantorvals, arXiv:2309.01589
-
[28]
Nitecki,Cantorvals and subsum sets of null sequences, Amer
Z. Nitecki,Cantorvals and subsum sets of null sequences, Amer. Math. Monthly122(2015), 862–870
2015
-
[29]
Nowakowski,On a new condition implying that an achievement set is a Cantorval and its applications, arXiv:2512.17761
P. Nowakowski,On a new condition implying that an achievement set is a Cantorval and its applications, arXiv:2512.17761
-
[30]
Nowakowski, F
P. Nowakowski, F. Prus-Wiśniowski,The Lebesgue measure of boundaries of multigeometric Cantorvals, arXiv:2510.21878
-
[31]
Nymann, R.A
J.E. Nymann, R.A. Sáenz,On a paper of Guthrie and Nymann on subsums of infinite series, Colloq. Math.83 (2000), 1–4. 15
2000
-
[32]
Pratsiovytyi, S
M.V. Pratsiovytyi, S. Ratushniak,On the properties of a certain perturbed binary sequence(in Ukrainian), Bukovinian Math. J.13(2025), 109–117
2025
-
[33]
Vinishin, V
Y. Vinishin, V. Markitan, M. Pratsiovytyi, I. Savchenko,Positive series, whose sets of subsums are Cantorvals, Proc. International Geom. Center12(2) (2019), 26–42 (in Ukrainian)
2019
-
[34]
Weinstein, B.E
A.D. Weinstein, B.E. Shapiro,On the structure of a set ofα-representable numbers, Izv. Vysš. Učebn. Zaved. Matematika.24(1980), 8–11. F aculty of Mathematics and Computer Science, University of Lodz, Banacha 22, 90-238 Łódź, Poland, ORCID: 0000-0002-3655-4991 Email address:pio...
1980
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