Before stating the conjecture, the notion of the radical of an integer must be introduced: for a positive integer n {\displaystyle n} , the radical of n {\displaystyle n} , denoted rad ( n ) {\displaystyle {\text{rad}}(n)} , is the product of the distinct prime factors of n {\displaystyle n} . For example,
rad ( 16 ) = rad ( 2 4 ) = rad ( 2 ) = 2 {\displaystyle {\text{rad}}(16)={\text{rad}}(2^{4})={\text{rad}}(2)=2}
rad ( 17 ) = 17 {\displaystyle {\text{rad}}(17)=17}
rad ( 18 ) = rad ( 2 ⋅ 3 2 ) = 2 ⋅ 3 = 6 {\displaystyle {\text{rad}}(18)={\text{rad}}(2\cdot 3^{2})=2\cdot 3=6}
rad ( 1000000 ) = rad ( 2 6 ⋅ 5 6 ) = 2 ⋅ 5 = 10 {\displaystyle {\text{rad}}(1000000)={\text{rad}}(2^{6}\cdot 5^{6})=2\cdot 5=10}
If a, b, and c are coprime10 positive integers such that a + b = c, it turns out that "usually" c < rad ( a b c ) {\displaystyle c<{\text{rad}}(abc)} . The abc conjecture deals with the exceptions. Specifically, it states that:
An equivalent formulation is:
Equivalently (using the little o notation):
A fourth equivalent formulation of the conjecture involves the quality q(a, b, c) of the triple (a, b, c), which is defined as
For example:
A typical triple (a, b, c) of coprime positive integers with a + b = c will have c < rad(abc), i.e. q(a, b, c) < 1. Triples with q > 1 such as in the second example are rather special, they consist of numbers divisible by high powers of small prime numbers. The fourth formulation is:
Whereas it is known that there are infinitely many triples (a, b, c) of coprime positive integers with a + b = c such that q(a, b, c) > 1, the conjecture predicts that only finitely many of those have q > 1.01 or q > 1.001 or even q > 1.0001, etc. In particular, if the conjecture is true, then there must exist a triple (a, b, c) that achieves the maximal possible quality q(a, b, c).
The condition that ε > 0 is necessary as there exist infinitely many triples a, b, c with c > rad(abc). For example, let
The integer b is divisible by 9:
Using this fact, the following calculation is made:
By replacing the exponent 6n with other exponents forcing b to have larger square factors, the ratio between the radical and c can be made arbitrarily small. Specifically, let p > 2 be a prime and consider
Now it may be plausibly claimed that b is divisible by p2:
The last step uses the fact that p2 divides 2p(p−1) − 1. This follows from Fermat's little theorem, which shows that, for p > 2, 2p−1 = pk + 1 for some integer k. Raising both sides to the power of p then shows that 2p(p−1) = p2(...) + 1.
And now with a similar calculation as above, the following results:
A list of the highest-quality triples (triples with a particularly small radical relative to c) is given below; the highest quality, 1.6299, was found by Eric Reyssat (Lando & Zvonkin 2004, p. 137) for
The abc conjecture has a large number of consequences. These include both known results (some of which have been proven separately only since the conjecture has been stated) and conjectures for which it gives a conditional proof. The consequences include:
The abc conjecture implies that c can be bounded above by a near-linear function of the radical of abc. Bounds are known that are exponential. Specifically, the following bounds have been proven:
In these bounds, K1 and K3 are constants that do not depend on a, b, or c, and K2 is a constant that depends on ε (in an effectively computable way) but not on a, b, or c. The bounds apply to any triple for which c > 2.
There are also theoretical results that provide a lower bound on the best possible form of the abc conjecture. In particular, Stewart & Tijdeman (1986) showed that there are infinitely many triples (a, b, c) of coprime integers with a + b = c and
for all k < 4. The constant k was improved to k = 6.068 by van Frankenhuysen (2000).
In 2006, the Mathematics Department of Leiden University in the Netherlands, together with the Dutch Kennislink science institute, launched the ABC@Home project, a grid computing system, which aims to discover additional triples a, b, c with rad(abc) < c. Although no finite set of examples or counterexamples can resolve the abc conjecture, it is hoped that patterns in the triples discovered by this project will lead to insights about the conjecture and about number theory more generally.
As of May 2014, ABC@Home had found 23.8 million triples.30
Note: the quality q(a, b, c) of the triple (a, b, c) is defined above.
The abc conjecture is an integer analogue of the Mason–Stothers theorem for polynomials.
A strengthening, proposed by Baker (1998), states that in the abc conjecture one can replace rad(abc) by
where ω is the total number of distinct primes dividing a, b and c.32
Andrew Granville noticed that the minimum of the function ( ε − ω rad ( a b c ) ) 1 + ε {\displaystyle {\big (}\varepsilon ^{-\omega }\operatorname {rad} (abc){\big )}^{1+\varepsilon }} over ε > 0 {\displaystyle \varepsilon >0} occurs when ε = ω log ( rad ( a b c ) ) . {\displaystyle \varepsilon ={\frac {\omega }{\log {\big (}\operatorname {rad} (abc){\big )}}}.}
This inspired Baker (2004) to propose a sharper form of the abc conjecture, namely:
with κ an absolute constant. After some computational experiments he found that a value of 6 / 5 {\displaystyle 6/5} was admissible for κ. This version is called the "explicit abc conjecture".
Baker (1998) also describes related conjectures of Andrew Granville that would give upper bounds on c of the form
where Ω(n) is the total number of prime factors of n, and
where Θ(n) is the number of integers up to n divisible only by primes dividing n.
Robert, Stewart & Tenenbaum (2014) proposed a more precise inequality based on Robert & Tenenbaum (2013). Let k = rad(abc). They conjectured there is a constant C1 such that
holds whereas there is a constant C2 such that
holds infinitely often.
Browkin & Brzeziński (1994) formulated the n conjecture—a version of the abc conjecture involving n > 2 integers.
Lucien Szpiro proposed a solution in 2007, but it was found to be incorrect shortly afterwards.33
Since August 2012, Shinichi Mochizuki has claimed a proof of Szpiro's conjecture and therefore the abc conjecture.34 He released a series of four preprints developing a new theory he called inter-universal Teichmüller theory (IUTT), which is then applied to prove the abc conjecture.35 The papers have not been widely accepted by the mathematical community as providing a proof of abc.36 This is not only because of their length and the difficulty of understanding them,37 but also because at least one specific point in the argument has been identified as a gap by some other experts.38 Although a few mathematicians have vouched for the correctness of the proof39 and have attempted to communicate their understanding via workshops on IUTT, they have failed to convince the number theory community at large.4041
In March 2018, Peter Scholze and Jakob Stix visited Kyoto for discussions with Mochizuki.4243 While they did not resolve the differences, they brought them into clearer focus. Scholze and Stix wrote a report asserting and explaining an error in the logic of the proof and claiming that the resulting gap was "so severe that ... small modifications will not rescue the proof strategy";44 Mochizuki claimed that they misunderstood vital aspects of the theory and made invalid simplifications.454647
On April 3, 2020, two mathematicians from the Kyoto research institute where Mochizuki works announced that his claimed proof would be published in Publications of the Research Institute for Mathematical Sciences, the institute's journal. Mochizuki is chief editor of the journal but recused himself from the review of the paper.48 The announcement was received with skepticism by Kiran Kedlaya and Edward Frenkel, as well as being described by Nature as "unlikely to move many researchers over to Mochizuki's camp".49 In March 2021, Mochizuki's proof was published in RIMS.50
Oesterlé 1988. - Oesterlé, Joseph (1988), "Nouvelles approches du "théorème" de Fermat", Astérisque, Séminaire Bourbaki exp 694 (161): 165–186, ISSN 0303-1179, MR 0992208 http://www.numdam.org/item?id=SB_1987-1988__30__165_0 ↩
Masser 1985. - Masser, D. W. (1985). "Open problems". In Chen, W. W. L. (ed.). Proceedings of the Symposium on Analytic Number Theory. London: Imperial College. ↩
Goldfeld 1996. - Goldfeld, Dorian (1996). "Beyond the last theorem". Math Horizons. 4 (September): 26–34. doi:10.1080/10724117.1996.11974985. JSTOR 25678079. https://doi.org/10.1080%2F10724117.1996.11974985 ↩
Fesenko, Ivan (September 2015). "Arithmetic deformation theory via arithmetic fundamental groups and nonarchimedean theta-functions, notes on the work of Shinichi Mochizuki". European Journal of Mathematics. 1 (3): 405–440. doi:10.1007/s40879-015-0066-0. https://doi.org/10.1007%2Fs40879-015-0066-0 ↩
Ball, Peter (10 September 2012). "Proof claimed for deep connection between primes". Nature. doi:10.1038/nature.2012.11378. Retrieved 19 March 2018. https://www.nature.com/news/proof-claimed-for-deep-connection-between-primes-1.11378 ↩
Castelvecchi, Davide (9 April 2020). "Mathematical proof that rocked number theory will be published". Nature. 580 (7802): 177. Bibcode:2020Natur.580..177C. doi:10.1038/d41586-020-00998-2. PMID 32246118. S2CID 214786566. /wiki/Bibcode_(identifier) ↩
Further comment by P. Scholze at Not Even Wrong math.columbia.edu[self-published source?] https://www.math.columbia.edu/~woit/wordpress/?p=11709&cpage=1#comment-235940 ↩
Scholze, Peter. "Review of inter-universal Teichmüller Theory I". zbmath open. Retrieved 2025-02-25. https://zbmath.org/1465.14002 ↩
When a + b = c, any common factor of two of the values is necessarily shared by the third. Thus, coprimality of a, b, c implies pairwise coprimality of a, b, c. So in this case, it does not matter which concept we use. /wiki/Pairwise_coprime ↩
Waldschmidt 2015. - Waldschmidt, Michel (2015). "Lecture on the abc Conjecture and Some of Its Consequences" (PDF). Mathematics in the 21st Century. Springer Proceedings in Mathematics & Statistics. Vol. 98. pp. 211–230. doi:10.1007/978-3-0348-0859-0_13. ISBN 978-3-0348-0858-3. https://webusers.imj-prg.fr/~michel.waldschmidt/articles/pdf/abcLahoreProceedings.pdf ↩
Elkies (1991). - Elkies, N. D. (1991). "ABC implies Mordell". International Mathematics Research Notices. 1991 (7): 99–109. doi:10.1155/S1073792891000144. https://doi.org/10.1155%2FS1073792891000144 ↩
Van Frankenhuijsen (2002). - Van Frankenhuijsen, Machiel (2002). "The ABC conjecture implies Vojta's height inequality for curves". J. Number Theory. 95 (2): 289–302. doi:10.1006/jnth.2001.2769. MR 1924103. https://doi.org/10.1006%2Fjnth.2001.2769 ↩
Langevin (1993). - Langevin, M. (1993). "Cas d'égalité pour le théorème de Mason et applications de la conjecture abc". Comptes rendus de l'Académie des sciences (in French). 317 (5): 441–444. ↩
Silverman (1988). - Silverman, Joseph H. (1988). "Wieferich's criterion and the abc-conjecture". Journal of Number Theory. 30 (2): 226–237. doi:10.1016/0022-314X(88)90019-4. Zbl 0654.10019. https://doi.org/10.1016%2F0022-314X%2888%2990019-4 ↩
Nitaj (1996). - Nitaj, Abderrahmane (1996). "La conjecture abc". Enseign. Math. (in French). 42 (1–2): 3–24. ↩
Granville, Andrew; Tucker, Thomas (2002). "It's As Easy As abc" (PDF). Notices of the AMS. 49 (10): 1224–1231. https://www.ams.org/notices/200210/fea-granville.pdf ↩
Pomerance (2008). - Pomerance, Carl (2008). "Computational Number Theory". The Princeton Companion to Mathematics. Princeton University Press. pp. 361–362. ↩
Granville & Stark (2000). - Granville, Andrew; Stark, H. (2000). "ABC implies no "Siegel zeros" for L-functions of characters with negative exponent" (PDF). Inventiones Mathematicae. 139 (3): 509–523. Bibcode:2000InMat.139..509G. doi:10.1007/s002229900036. S2CID 6901166. http://www.dms.umontreal.ca/~andrew/PDF/NoSiegelfinal.pdf ↩
The ABC-conjecture, Frits Beukers, ABC-DAY, Leiden, Utrecht University, 9 September 2005. http://www.math.uu.nl/people/beukers/ABCpresentation.pdf ↩
Mollin (2009); Mollin (2010, p. 297) - Mollin, R.A. (2009). "A note on the ABC-conjecture" (PDF). Far East Journal of Mathematical Sciences. 33 (3): 267–275. ISSN 0972-0871. Zbl 1241.11034. Archived from the original (PDF) on 2016-03-04. Retrieved 2013-06-14. https://web.archive.org/web/20160304053930/http://people.ucalgary.ca/~ramollin/abcconj.pdf ↩
Browkin (2000, p. 10) - Browkin, Jerzy (2000). "The abc-conjecture". In Bambah, R. P.; Dumir, V. C.; Hans-Gill, R. J. (eds.). Number Theory. Trends in Mathematics. Basel: Birkhäuser. pp. 75–106. ISBN 3-7643-6259-6. https://archive.org/details/numbertheory00bamb_636 ↩
Granville (1998). - Granville, A. (1998). "ABC Allows Us to Count Squarefrees" (PDF). International Mathematics Research Notices. 1998 (19): 991–1009. doi:10.1155/S1073792898000592. http://www.dms.umontreal.ca/~andrew/PDF/polysq3.pdf ↩
Pasten, Hector (2017), "Definability of Frobenius orbits and a result on rational distance sets", Monatshefte für Mathematik, 182 (1): 99–126, doi:10.1007/s00605-016-0973-2, MR 3592123, S2CID 7805117 /wiki/Monatshefte_f%C3%BCr_Mathematik ↩
arXiv:math/0408168 Andrea Surroca, Siegel’s theorem and the abc conjecture, Riv. Mat. Univ. Parma (7) 3, 2004, S. 323–332 /wiki/ArXiv_(identifier) ↩
"Synthese resultaten", RekenMeeMetABC.nl (in Dutch), archived from the original on December 22, 2008, retrieved October 3, 2012. https://web.archive.org/web/20081222221716/http://rekenmeemetabc.nl/?item=h_stats ↩
"Data collected sofar", ABC@Home, archived from the original on May 15, 2014, retrieved April 30, 2014 https://web.archive.org/web/20140515021303/http://abcathome.com/data/ ↩
"100 unbeaten triples". Reken mee met ABC. 2010-11-07. http://www.math.leidenuniv.nl/~desmit/abc/index.php?set=2 ↩
Bombieri & Gubler (2006), p. 404. - Bombieri, Enrico; Gubler, Walter (2006). Heights in Diophantine Geometry. New Mathematical Monographs. Vol. 4. Cambridge University Press. ISBN 978-0-521-71229-3. Zbl 1130.11034. https://zbmath.org/?format=complete&q=an:1130.11034 ↩
"Finiteness Theorems for Dynamical Systems", Lucien Szpiro, talk at Conference on L-functions and Automorphic Forms (on the occasion of Dorian Goldfeld's 60th Birthday), Columbia University, May 2007. See Woit, Peter (May 26, 2007), "Proof of the abc Conjecture?", Not Even Wrong. /wiki/Peter_Woit ↩
Mochizuki, Shinichi (4 March 2021). "Inter-universal Teichmüller Theory IV: Log-Volume Computations and Set-Theoretic Foundations". Publications of the Research Institute for Mathematical Sciences. 57 (1): 627–723. doi:10.4171/PRIMS/57-1-4. S2CID 3135393. /wiki/Doi_(identifier) ↩
Calegari, Frank (December 17, 2017). "The ABC conjecture has (still) not been proved". Retrieved March 17, 2018. /wiki/Frank_Calegari ↩
Revell, Timothy (September 7, 2017). "Baffling ABC maths proof now has impenetrable 300-page 'summary'". New Scientist. https://www.newscientist.com/article/2146647-baffling-abc-maths-proof-now-has-impenetrable-300-page-summary/ ↩
Scholze, Peter; Stix, Jakob. "Why abc is still a conjecture" (PDF). Archived from the original (PDF) on February 8, 2020. Retrieved September 23, 2018. (updated version of their May report Archived 2020-02-08 at the Wayback Machine) /wiki/Peter_Scholze ↩
Fesenko, Ivan (28 September 2016). "Fukugen". Inference. 2 (3). Retrieved 30 October 2021. /wiki/Ivan_Fesenko ↩
Conrad, Brian (December 15, 2015). "Notes on the Oxford IUT workshop by Brian Conrad". Retrieved March 18, 2018. /wiki/Brian_Conrad ↩
Castelvecchi, Davide (8 October 2015). "The biggest mystery in mathematics: Shinichi Mochizuki and the impenetrable proof". Nature. 526 (7572): 178–181. Bibcode:2015Natur.526..178C. doi:10.1038/526178a. PMID 26450038. https://doi.org/10.1038%2F526178a ↩
Klarreich, Erica (September 20, 2018). "Titans of Mathematics Clash Over Epic Proof of ABC Conjecture". Quanta Magazine. /wiki/Erica_Klarreich ↩
"March 2018 Discussions on IUTeich". Retrieved October 2, 2018. Web-page by Mochizuki describing discussions and linking consequent publications and supplementary material http://www.kurims.kyoto-u.ac.jp/~motizuki/IUTch-discussions-2018-03.html ↩
Mochizuki, Shinichi. "Report on Discussions, Held during the Period March 15 – 20, 2018, Concerning Inter-Universal Teichmüller Theory" (PDF). Retrieved February 1, 2019. the ... discussions ... constitute the first detailed, ... substantive discussions concerning negative positions ... IUTch. /wiki/Shinichi_Mochizuki ↩
Mochizuki, Shinichi (July 2018). "Comments on the manuscript by Scholze-Stix concerning Inter-Universal Teichmüller Theory" (PDF). S2CID 174791744. Retrieved October 2, 2018. /wiki/Shinichi_Mochizuki ↩
Mochizuki, Shinichi. "Comments on the manuscript (2018-08 version) by Scholze-Stix concerning Inter-Universal Teichmüller Theory" (PDF). Retrieved October 2, 2018. /wiki/Shinichi_Mochizuki ↩
Mochizuki, Shinichi. "Mochizuki's proof of ABC conjecture". Retrieved July 13, 2021. /wiki/Shinichi_Mochizuki ↩