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Problem 934
claims/: The 5 claim pages of Problem 934, one per claimant's result; the problem's standing derives from them.
Statement. Let be minimal such that every graph with edges and maximal degree contains two edges whose shortest path between them has length .
Estimate .
Formulation. The site's wording as of 2026-09-19, last edited 28 October 2025. The distance between two edges is the length of a shortest path joining an endpoint of one to an endpoint of the other, one less than their distance in the line graph, so is the largest number of edges of a graph of maximum degree at most whose line graph has diameter at most (the 2022 paper's reading, p. 1). The statement is a request for estimates and asserts nothing; the page-level status is open as the site's, and nothing is defective in the wording. Two side remarks. The site's holds for and fails at , where has three pairwise intersecting edges and (the thread's correction, conceded by the site's author on 25 March 2026; the 2022 paper prints the same unqualified sentence). Erdős's 1988 text says "The order of magnitude of is easily seen to be [sic]" (p. 81), one power above the of the later normalization (, ); recorded as printed. The site's two displayed conjectures of 2022 are variants recorded below, not the question.
Status. Open. No estimate of up to a factor for general , and no "nice expression" in Erdős's sense, was found in the search whose scope the Current assessment records. Known exactly: for ; for even and for odd (Chung, Gyárfás, Tuza and Trotter 1990, refereed; an accepted partial claim on its claim page); (Cambie, Cames van Batenburg, de Joannis de Verclos and Kang, SIAM J. Discrete Math. 2022, refereed; an accepted partial claim on its claim page). In general for all and for all large and infinitely many (the same paper), with for graphs without a -cycle. Two preprints of 2026 change the picture at and for the asymptotics: Kumar, Mohar and Pragada refute the 2022 conjecture at () and prove (a pending partial claim on its claim page), and Korsky claims on the site's proof-claim tab, and Cames van Batenburg and Korsky in a preprint, as for every (the preprint's abstract states it for every ), a result first submitted to the tab on 29 July 2026 and recorded as a pending partial claim on its claim page; both are unrefereed and recorded as claimed progress. A thread post and Zenodo manuscript of 17 August 2026 claim the exact value with a Lean 4 development, a pending partial claim on its claim page. This is a bounded negative finding, not a certificate of openness.
Source. erdosproblems.com/934, accessed 2026-09-19: the problem page (labeled OPEN, with the site's note that no finite computation can settle it; last edited 28 October 2025; source keys [BBPP83], [CCJK22], [CGTT90], [Er88]; "Formalised statement? No"; OEIS "Possible"), its six-comment discussion thread (24 March 2026 to 17 August 2026) and its proof-claim tab with one partial claim (29 July 2026). Cite as: T. F. Bloom, Erdős Problem #934, https://www.erdosproblems.com/934, accessed 2026-09-19.
References.
- [Er88] Erdős, P., Problems and results in combinatorial analysis and graph theory. Discrete Math. 72 (1988), 81--92; Section 1, printed p. 81. Library home: erdos_1988_problems_results_combinatorial_analysis_graph_theory.
- [BBPP83] Bermond, J.-C., Bond, J., Paoli, M. and Peyrat, C., Graphs and interconnection networks: diameter and vulnerability. Surveys in Combinatorics 1983 (Proc. Ninth British Combinatorial Conference), London Math. Soc. Lecture Note Ser. 82 (1983), 1--30 (the venue from the citing papers; the site's text prints "(1983), 1-30"). The HAL deposit is a two-up scan of the typescript without page numbers; in it the passage is on PDF p. 13 (left- and right-hand typescript pages) and the Kleitman reference on PDF p. 16 (the list begins on PDF p. 14). Library home: bermond_1983_graphs_interconnection_networks_diameter_vulnerability; paged at conjecture_p13.
- [CGTT90] Chung, F. R. K., Gyárfás, A., Tuza, Z. and Trotter, W. T., The maximum number of edges in -free graphs of bounded degree. Discrete Math. 81 (1990), no. 2, 129--135, doi:10.1016/0012-365X(90)90144-7 (the site's text prints no volume). Theorem 4, p. 131; the attribution, p. 129. Library home: chung_1990_maximum_number_edges_2k2_free_graphs_bounded_degree (the author's copy on W. T. Trotter's publication page); paged at theorem_4.
- [CCJK22] Cambie, S., Cames van Batenburg, W., de Joannis de Verclos, R. and Kang, R. J., Maximising line subgraphs of diameter at most . SIAM J. Discrete Math. 36 (2022), no. 2, 939--950, doi:10.1137/21M1437354 (the site's text spells "Maximizing"). Pages are those of arXiv:2103.11898v2 (10 December 2021, "v2 accepted to SIAM Journal on Discrete Mathematics", 12 pp.); the introduction, p. 1; Conjecture 1, Theorem 2, Conjectures 3--4 and Proposition 5, p. 2; Theorems 6--8 and Corollary 9, p. 3; Theorem 10, p. 4. Library home: cambie_2022_maximizing_line_subgraphs_diameter_at_most_t; paged at theorem_6, theorem_7, theorem_2, proposition_5, conjecture_1, conjecture_3 and conjecture_4.
- [FGST89] Faudree, R. J., Gyárfás, A., Schelp, R. H. and Tuza, Zs., Induced matchings in bipartite graphs. Discrete Math. 78 (1989), 83--87; printed p. 83, the attribution of the question and value. Not a site key for this problem. Library home: faudree_1989_induced_matchings_bipartite_graphs; paged at problem_p83.
- [KMP26] Kumar, H., Mohar, B. and Pragada, S., An improved bound for the strong clique index of graphs. arXiv:2607.02698v1 (2 July 2026), 15 pp.; a preprint, cited at the pages of its arXiv PDF (Conjectures 1.9--1.10, Theorem 1.11 and Problem 1.12, p. 4; Lemma 3.1 and the display, p. 9; Lemma 3.2's display, p. 10; the "AI statement", p. 13). Library home: kumar_2026_improved_bound_strong_clique_index_graphs; paged at lemma_3_1 and theorem_1_11.
- [CvBK26] Cames van Batenburg, W. and Korsky, S., Asymptotically attaining the Moore bound. arXiv:2608.03965v1 (4 August 2026), "7+ε pages"; a preprint; its arXiv record (abstract only).
Formalization. None. formal-conjectures has no file ErdosProblems/934.lean
at main the site's indicator reads "Formalised statement? No",
and the community database (teorth/erdosproblems, data/problems.yaml as of
2026-09-19) lists the problem as open, unformalized and with no formal-proof
field as of its last update, dated 31 August 2025. A thread post of 17 August
2026 describes a Lean 4 proof of the single value in an external
repository, recorded on
its claim page;
it is not a formalization of the problem's statement, and the corpus has not
built it.
Current assessment
The question (site formulation of 2026-09-19). The statement above; OPEN; last edited 28 October 2025. The commentary attributes the problem to Erdős and Nešetřil and quotes Erdős's 1988 remark that the problem is interesting only if has a nice expression (quoted under The origin below); calls and easy; records the conjecture with equality for even , made independently by Erdős and Nešetřil and by Bermond, Bond, Paoli and Peyrat, with the proof credited to Chung, Gyárfás, Tuza and Trotter in [CGTT90] and a pointer to Problem 149; records the 2022 conjectures that , with equality exactly when is a prime power, and that for all , for infinitely many and for all , beside the value ; and records the same authors' bounds for infinitely many when is large and for all . The thread's six comments and the tab's one claim are recorded below; the community database says open, unformalized.
The origin. Erdős's 1988 paper, Section 1, printed p. 81 (the Er88 card's #934 row records the passage), poses the problem in one sentence: "One could perhaps try to determine the smallest integer so that every of edges each vertex of which has degree contains two edges so that the shortest path joining these edges has length ." He then calls the order of magnitude easy to see, printing it as (the Formulation note above records the slip), says the exact value is unknown, and adds the remark the site quotes: "This problem seems to be interesting only if there is a nice expression for ." The 1983 survey states the case in the language of hypergraphs of maximum degree (conjecture_p13, PDF p. 13 of the HAL deposit, left- and right-hand typescript pages): , the largest number of edges of a graph of maximum degree and line diameter ; the graph with edges and line diameter , so for even ; and "answering one of our conjectures, it has been shown by Kleitman (1983) that every graph of maximum degree and line diameter has at most vertices [edges]. Thus and if is even ", Kleitman's result being a "Private communication of Trotter" in the reference list; for general the survey records from Benson's and Delorme's bipartite graphs. The three attributions of the statement in the sources differ in emphasis and are recorded as printed: [CGTT90] (p. 129) solves "the following extremal problem posed by Bermond et al. in [7] and also by Nešetřil and Erdős"; [FGST89] (p. 83) says the case "was asked earlier by Bermond, Bond and Peyrat" and that "was shown in [1]", the survey; the survey itself reports Kleitman.
The cases and . For , two edges at distance at least are disjoint, and for a graph with edges and maximum degree at most has two disjoint edges while the star has not, so (the thread's argument of 25 March 2026; [CCJK22], p. 1, "the case is easy and "); for the graphs are paths and cycles, has three pairwise intersecting edges, and , more generally (the thread, 25 March 2026; the cycle has line diameter ). For , two edges at distance at least are strongly independent, and Theorem 4 of Chung, Gyárfás, Tuza and Trotter (p. 131) states that a connected graph with no induced and maximum degree at most has at most edges, with equality only for the blown-up five-cycle , where for even and for odd ; hence (authored, one line) a graph with edges and maximum degree at most has two strongly independent edges, in one component by the theorem or in two, and has none, so , the site's statement that with equality for even , and for odd . Acceptance evidence: Discrete Math. 81 (1990), refereed, cited from the author's copy of the journal pages; the accepted partial claim is its claim page. This is the "easier problem" of Problem 149.
The case . [[../library/extremal_graph_theory/cambie_2022_maximizing_line_subgraphs_diameter_at_most_t/theorem_2|Theorem 2 of Cambie, Cames van Batenburg, de Joannis de Verclos and Kang]] (p. 2): , "through a brief case analysis", the extremal graph being the Fano plane's incidence graph with one edge subdivided (p. 11). Their [[../library/extremal_graph_theory/cambie_2022_maximizing_line_subgraphs_diameter_at_most_t/conjecture_1|Conjecture 1]] (p. 2): ", with equality if is one more than a prime power", from the incidence graphs of projective planes ( edges, line diameter ) with one subdivided edge; the printed word is "if", not the site's "if and only if" (as arXiv v2 prints it; the thread of 17 August 2026 makes the same point). The preprint [KMP26] refutes it: Lemma 3.1 (p. 9) shows for the odd graph , which is -regular on vertices with edges, "By the above Lemma 3.1, it follows that . Thus, Conjecture 1.9 is false for "; the truncated Witt graph gives (p. 10); and Theorem 1.11 (p. 4), ". Equivalently, for every , and sufficiently large , we have ", refutes both Conjecture 1 for all large and the upper asymptotic conjecture at , with Problem 1.12 asking whether for all large . The preprint's "AI statement" (p. 13) reads "We acknowledge the use of AI tools during the ideation phase. We declare that the text is not AI-generated." It is unrefereed (arXiv v1, 2 July 2026; one citing record, [CvBK26]); the lemma for is a half-page argument on -subsets of a -set, and no review of it is recorded; the preprint's bounds are a pending partial claim on its claim page.
General . Theorem 6 (p. 3): for all , through (Theorem 8), improving the trivial ; Theorem 7 (p. 3): a -free graph of maximum degree with more than edges has line graph of diameter greater than (printed "at least" [sic], false at by the star and by ; for it follows from Theorem 10, ), asymptotically sharp for and, in Theorem 10's form, exact for , by the incidence graphs of generalized polygons; Proposition 5 (p. 2): for and infinitely many , from Canale and Gómez's degree--diameter graphs. Acceptance evidence: SIAM J. Discrete Math. 36 (2022), refereed (Crossref); the text cited is the accepted arXiv v2; the accepted partial claim is its claim page. The paper's two asymptotic conjectures, Conjecture 3 ( for infinitely many , the edge analog of Bollobás's degree--diameter conjecture, known for ) and Conjecture 4 ( for and large ), now stand as follows on the preprint record: Conjecture 4 fails at ([KMP26], Theorem 1.11, above; "Conjecture 1.10 remains undecided for "), and Conjecture 3 is claimed for every by [CvBK26], whose abstract states for the degree--diameter function (Bollobás's conjecture) and, "for every fixed , graphs of maximum degree at most and line-graph diameter at most with edges". Neither claim is refereed or, as far as the search found, independently reviewed. The 1983 survey's is a precursor of Conjecture 3 with a weaker constant.
Site-versus-source items (recorded, not resolved with the site). (a) The site's without the restriction , false at (the thread's correction, conceded; the 2022 paper's p. 1 is the source of the sentence and prints it the same way). (b) The site's version of the 2022 Conjecture 1 makes the paper's equality condition necessary and sufficient, where the paper prints only "if". (c) The two 2022 conjectures displayed as open, where a 2026 preprint refutes one and half of the other and another claims the remaining half; preprint status, so no correction of the site is implied. (d) Erdős's "" against the later , a slip in the origin recorded as printed.
Forum and proof-claim items (recorded with provenance, not status). The
thread: 24 March 2026 (the account Adenwalla) asks whether refutes
the site's ; 25 March 2026 (the site's author) agrees, saying the
sentence was taken from [CCJK22] and holds for but
fails at because of ; 25 March 2026 (the account StijnC) gives
the case () and the proof for ; 9 August 2026 (the
account Xiao Hu) announces the Korsky and Cames van Batenburg preprint,
arXiv:2608.03965; 17 August 2026, 13:33 (the account BitterLemma) posts the
three corrections above, citing [KMP26]'s Lemma 3.1 and Theorem 1.11 and a
third-party working report of 28 July 2026, with a signature describing the
poster as an AI-assisted project that checked the primary sources before
posting; 17 August 2026, 18:25 (BitterLemma) claims the exact value
with a machine-checked proof: the lower bound is [KMP26]'s, and
the matching upper bound is described as an elementary finite reduction
confining any extremal configuration to at most 80 vertices in four
breadth-first layers, a counting bound leaving at most 79 edges available,
and an exhaustive certified search over 123 surviving layer profiles, all
formalized in Lean 4 without sorry on the axioms propext,
Classical.choice and Quot.sound, the only outside input being the
unsatisfiability of 123 CNF formulas, each with an LRAT refutation, in a
repository bitterlemma/erdos-934, which holds the Lean development and
the manuscript, published the same day as a Zenodo deposit; the post's
provenance statement says that the mathematics, code, formalization and
text were produced with Claude (Anthropic) under human direction and
review, and that every externally checkable component was verified by a
pass independent of the one that produced it; the claim is recorded on
its claim page.
The proof-claim tab lists a partial proof claimed by
Samuel Korsky, naming the AI system GPT 5.6-Pro as a tool, submitted 2026-07-29
09:07:13, whose summary claims as for
by a construction from complete flags over for a prime
power , with an external link to a shared-drive file
(linked from its claim page) and three comments recorded on its
claim page; the
site's tab page carries its standing disclaimer that a listing is no
guarantee of correctness. The claim is the statement of Conjecture 3 later
posted as [CvBK26]. None of these items changes the status; the
value, if confirmed, would be one exact value at one .
Search scope. None of the routes below found an asymptotic determination of , a refereed change to the 2022 bounds, or a resolution of the site's request.
- The site: problem page, discussion thread and proof-claim tab; the formal-conjectures directory listing and tree (no file 934); the community database.
- arXiv: the API records of 2103.11898 (v1 22 March 2021, v2 10 December 2021, "v2 accepted to SIAM Journal on Discrete Mathematics"), 2607.02698 (v1, 2 July 2026), 2608.03965 (v1, 4 August 2026, "7+ε pages") and 2506.20976 (Abiad and Reijnders, "Eigenvalue bounds for distance-edge colorings", v2 23 March 2026, on the distance- chromatic index, abstract only; not this problem).
- Crossref bibliographic queries for [CGTT90] and [CCJK22] (volumes, pages, DOIs and dates as cited above).
- Semantic Scholar citation lists of [CCJK22] (four records: [CvBK26], [KMP26], arXiv:2506.20976 and a 2022 thesis on coloring squares of graphs) and [KMP26] (one record, [CvBK26]); the citation list of [CvBK26] was not obtained.
- W. T. Trotter's publication page for the [CGTT90] copy (HTTP 200).
- The primary sources: [Er88] p. 81; [CGTT90] pp. 129--131 and 135; [BBPP83] PDF pp. 9--16 of the HAL deposit; [CCJK22] pp. 1--4 and 11; [KMP26] pp. 1--4, 9, 10 and 13; [FGST89] p. 83.
Not searched: MathSciNet, zbMATH, Google Scholar, X. Not held: [CvBK26] (abstract only), the repository of the claim, the shared-drive file of the tab's claim, the journal text of [CCJK22], Canale--Gómez, Benson 1966 and Delorme 1983.
Remaining gaps. (1) Proof coverage: of [CCJK22] only Proposition 5's proof is followed, and of [KMP26] only Lemma 3.1's; nothing is independently reviewed. (2) [KMP26] and [CvBK26] are preprints; the refutation of the formula and of the upper asymptotic at , and the claimed lower asymptotic for every , await refereeing or an independent check. (3) The thread's exact value and the tab's claim rest on external manuscripts and code whose review is not recorded. (4) The journal text of [CCJK22] is not compared with the accepted arXiv v2. (5) Erdős's "" is recorded as printed and not explained.
Known results
- Erdős 1988, p. 81 and Bermond--Bond--Paoli--Peyrat 1983: the problem in the posers' words; the 1983 statement of the case with Kleitman's reported proof and the bound .
- Chung--Gyárfás--Tuza--Trotter, Theorem 4 (1990, refereed): for even , for odd ; for (elementary).
- Cambie--Cames van Batenburg--de Joannis de Verclos--Kang, Theorem 6 (2022, refereed): ; Theorem 7: for -free graphs; Proposition 5: for large and infinitely many ; Theorem 2: .
- Kumar--Mohar--Pragada, Lemma 3.1 and Theorem 1.11 (2026, preprint; a pending partial claim on its claim page): and , refuting Conjecture 1; , refuting Conjecture 4 at .
- [CvBK26] (2026, preprint, abstract): as for every , the claim of Conjecture 3.
Linked library material
These entries are derived from explicit links on library pages. They are navigation only and do not by themselves record mathematical progress.
- bermond_1983_graphs_interconnection_networks_diameter_vulnerability
- bermond_1983_graphs_interconnection_networks_diameter_vulnerability / conjecture_p13
- cambie_2022_maximizing_line_subgraphs_diameter_at_most_t
- cambie_2022_maximizing_line_subgraphs_diameter_at_most_t / conjecture_1
- cambie_2022_maximizing_line_subgraphs_diameter_at_most_t / conjecture_3
- cambie_2022_maximizing_line_subgraphs_diameter_at_most_t / conjecture_4
- cambie_2022_maximizing_line_subgraphs_diameter_at_most_t / proposition_5
- cambie_2022_maximizing_line_subgraphs_diameter_at_most_t / theorem_2
- cambie_2022_maximizing_line_subgraphs_diameter_at_most_t / theorem_6
- cambie_2022_maximizing_line_subgraphs_diameter_at_most_t / theorem_7
- chung_1990_maximum_number_edges_2k2_free_graphs_bounded_degree
- chung_1990_maximum_number_edges_2k2_free_graphs_bounded_degree / theorem_4
- erdos_1988_problems_results_combinatorial_analysis_graph_theory
- faudree_1989_induced_matchings_bipartite_graphs
- faudree_1989_induced_matchings_bipartite_graphs / problem_p83
- kumar_2026_improved_bound_strong_clique_index_graphs
- kumar_2026_improved_bound_strong_clique_index_graphs / lemma_3_1
- kumar_2026_improved_bound_strong_clique_index_graphs / theorem_1_11