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Unit fraction representations using shifted Golomb primes

Number Theory · Submitted 4 Nov 2026 · 33 references

Pith's verdict: A real theorem for a genuinely sparse sequence — the supporting AP and non-smooth estimates are the durable part — but Proposition 6.1's stated hypotheses contradict each other and don't cover the way Section 6 uses it.

T0 · AI review

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arXiv ID2611.06798 (version 1)
Pith IDE7D6AT42, Pith's permanent record of this paper and its review
CitationRishika Agrawal. "Unit fraction representations using shifted Golomb primes." arXiv:2611.06798 (2026). https://pith.science/paper/E7D6AT42
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The paper

The paper claims

The paper proves that for every fixed nonzero integer $h$, the numbers $g-h$ with $g$ a Golomb prime form a reciprocal basis for the positive rationals: every $a/b$, subject only to the congruence conditions the problem forces, is a…

The reading

This paper asks how thin a set of integers can be and still write every positive rational number as a sum of distinct reciprocals of its members, and answers with the shifted Golomb primes. Golomb primes are produced by running the sieve of Eratosthenes but striking out the residue class $1$ instead of the class $0$, giving $3, 5, 17, 23, 29, 53, \dots$; they are far sparser than the primes, making up only about a $1/\log\log x$ proportion of the primes up to $x$, with reciprocal sum growing like $\log\log\log x$. That sparsity puts them out of reach of the known theorem for shifted primes, which needs positive relative density in the primes. The author proves that for any nonzero fixed $h$ and any coprime $a,b$ satisfying the congruence conditions forced by the problem, every $a/b$ is a finite sum of distinct unit fractions $1/(g-h)$ with $g$ a Golomb prime, and every such $g$ can be taken larger than any preassigned bound. If this holds, the reciprocal-basis phenomenon survives at the very edge of what current machinery allows, and it arrives with a new equidistribution theorem for Golomb primes in short arithmetic progressions, plus a bound saying at least about three quarters of shifted Golomb primes are power-smooth.

What carries the argument

The engine is a Croot-type proposition (Proposition 6.1): for a set $A$ of shifted primes inside an interval $(M,N]$ whose elements are $N^{0.99}$-power-smooth, carry about $\log\log N$ prime factors, spread their reciprocal mass evenly over prime powers, and have $R(A)$ not too small, one can hit every target of the shape $x/Q$ (with $Q=\mathrm{lcm}(A)$) by a sub-sum of reciprocals. The obstruction is that inside a single narrow interval the shifted Golomb primes have reciprocal sum only of order $1/\log\log N$, far too little to reach a fixed fraction. The author's fix is to slice the range into $J\asymp 333\log\log N$ blocks $(N_{j+1},N_j]$ with $N_{j+1}=N_j e^{-0.003}$, each contributing $\Theta(1/\log\log N)$, prune each block to satisfy the proposition using Theorem 1.4 and Theorem 1.5, and then arrange one integer $P$, divisible by $b$ and of size about $(\log\log N)^2$, that divides the lcm of every pruned block. That shared modulus lets the fractions $y_j/P$ be represented block by block and summed to $a/b$ with all denominators distinct.

Extended reading notes

Core claim

The central claim is Theorem 1.3: let $h\neq 0$ and let $a,b\in\mathbb{Z}^+$ with $(a,b)=1$, $(b,h)=1$ and $(b,h-1)$ Golomb-prime-free; then for every $y\ge |h|$ there is a finite set $B$ of Golomb primes, all exceeding $y$, with $a/b=\sum_{g\in B} 1/(g-h)$. The two conditions on $b$ are shown in Section 6 to be necessary, not technical: if a prime $p$ divided both $b$ and $h$ then $p$ would have to equal some $g>|h|\ge p$, and if a Golomb prime $q$ divided both $b$ and $h-1$ then $q\mid g-1$, which the defining sieve forbids. The proof rests on two new distribution results: a Siegel--Walfisz-type asymptotic for $|\{g\le x : g\equiv h \pmod b\}|$ that holds for $b\le(\log x)^A$ with the expected Euler-product correction for Golomb primes dividing $b$, and an upper bound saying that among Golomb primes $g\le x$ in the class $h \bmod b$, at most a proportion $0.259+o(1)$ have $g-h$ divisible by a prime power exceeding $x^{0.99}$.

Load-bearing premise

The deduction applies Proposition 6.1 to blocks whose endpoints satisfy $M=N_{j+1}=N_j e^{-0.003}$, whereas the proposition as printed requires $M\le N/10^4$; the appendix appears to use only $M\ge N^{0.997}$, so the main theorem is formally resting on the proposition holding in that wider range rather than the stated one.

Editorial extensions

If this is right

  • The reciprocal sum over shifted Golomb primes inherits a basis property: for every nonzero $h$ and every target fraction, one can reach or exceed it using distinct terms $1/(g-h)$, so the associated series diverges and is unbounded on distinct terms.
  • Golomb primes are equidistributed among the allowed residue classes $h \bmod b$ for $b\le(\log x)^A$, with the same $1/\varphi(b)$ factor as the primes and an explicit correction $\prod_{q\mid b, q\in G}(1-1/(q-1))^{-1}$ for Golomb primes dividing the modulus.
  • At least a positive proportion, roughly $0.741$ of the expected count, of shifted Golomb primes in a progression remain after discarding those with a prime-power divisor above $x^{0.99}$, which is what makes the Croot-type proposition applicable at all.
  • A remark in the paper observes that a recently announced zero-free half-plane $\mathrm{Re}\,s>7/8$ for Dirichlet $L$-functions would push the equidistribution theorem from $b\le(\log x)^A$ to $b\le x^{1/8-2\varepsilon}$ with the same method.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • The Golomb primes are one instance of a family: primes sieved by forbidding one residue class modulo each earlier member. The same three ingredients used here (equidistribution in progressions, a bound on non-smooth shifts, and a shared modulus across blocks) should give reciprocal-basis theorems for other sieves of this shape, so the argument reads as a template rather than a one-off.
  • The author states the method does not extend to an arbitrary positive-density subset of the Golomb primes, which leaves an obvious gradient to test: whether a random subset of the Golomb primes of relative density $(\log\log x)^{-\theta}$ still represents every rational, and where the threshold sits.
  • The common-modulus step is the part most likely to generalise beyond this paper's setting: any sparse set whose elements' least common multiples can be forced to carry a fixed modulus of size $\mathrm{polylog}\log$ can be assembled block by block, which suggests a reusable criterion independent of the specific arithmetic of Golomb primes.
  • A concrete check a reader can run: take the smallest cases, such as $h=1$, $a/b=1/2$, and search for short explicit subsets of $\{g-1\}$ summing to it, to see the block structure and modulus in action at small scale.
Original abstract

We prove that every positive rational number is a sum of distinct unit fractions with denominators of the form $g-h$, where $g$ is a Golomb prime and $h$ is a fixed nonzero integer, as long as the necessary congruence conditions are satisfied. Golomb primes, introduced by Golomb in 1955, are a natural analogue of the primes. Erd\H{o}s showed that the relative density of Golomb primes among the primes up to $N$ is about $1/\log\log N$, so they form a sparse subset of the primes. Our result is an analogue of Bloom's result on unit fraction representations using shifted primes, for this sparse subset of the primes. A key ingredient in our proof is a Siegel--Walfisz-type theorem for Golomb primes in arithmetic progressions, which we also prove here.

The compiled record

The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.

Compiled by classifier-1.13.0 via TypeSafe API, question bank abstract-p1-20260923, 2026-11-05: 1 request, 4,337 input tokens.

What the abstract itself states, as probabilities: claims first 0.07 · states limitation 0.86 · human participants 0.01 · controlled comparison 0.02 · randomized assignment 0.01 · states quantitative result 0.53 · compares with prior results 0.96 · mentions code or data availability 0.02.

The abstract, sentence by sentence

arXiv listing abstract v1. Results and the main claim are underlined; .

We prove that every positive rational number is a sum of distinct unit fractions with denominators of the form $g-h$, where $g$ is a Golomb prime and $h$ is a fixed nonzero integer, as long as the necessary congruence conditions are satisfied. Golomb primes, introduced by Golomb in 1955, are a natural analogue of the primes. Erd\H{o}s showed that the relative density of Golomb primes among the primes up to $N$ is about $1/\log\log N$, so they form a sparse subset of the primes. Our result is an analogue of Bloom's result on unit fraction representations using shifted primes, for this sparse subset of the primes. A key ingredient in our proof is a Siegel--Walfisz-type theorem for Golomb primes in arithmetic progressions, which we also prove here.

background contribution method result interpretation main claim

What the classifier reports for each sentence. The number is the probability it gave the label.
#sentencerolethe authors' own workstates the main conclusionstrength
s0 We prove that every positive rational number is a sum of distinct unit fractions with denominators of the form $g-h$, where $g$ is a Golomb prime and $h$ is a fixed nonzero integer, as long as the necessary congruence conditions are satisfied. result 0.86 0.96 0.96 asserted 1.00
s1 Golomb primes, introduced by Golomb in 1955, are a natural analogue of the primes. background 1.00 0.04 0.01 asserted 1.00
s2 Erd\H{o}s showed that the relative density of Golomb primes among the primes up to $N$ is about $1/\log\log N$, so they form a sparse subset of the primes. background 1.00 0.03 0.02 asserted 0.99
s3 Our result is an analogue of Bloom's result on unit fraction representations using shifted primes, for this sparse subset of the primes. interpretation 0.85 0.63 0.08 asserted 1.00
s4 A key ingredient in our proof is a Siegel--Walfisz-type theorem for Golomb primes in arithmetic progressions, which we also prove here. method 0.68 0.96 0.03 asserted 1.00

What kind of paper the classifier reports this is: theoretical result 1.00 · evidence from proof or derivation 1.00.

What was examined, and what was not

sources read
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not examined
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  • figures and tables
  • references and citing sentences
  • relations to other papers
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Every quoted sentence on this record is the authors'. Every label is from Pith's closed vocabulary, with the probability shown beside it. Every number in the measurements table is the authors', checked by code. Record as JSON

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Discussion

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