# Which math paper maximizes the ratio (importance)/(length)?

My vote would be Milnor's 7-page paper "On manifolds homeomorphic to the 7-sphere", in Vol. 64 of Annals of Math. For those who have not read it, he explicitly constructs smooth 7-manifolds which are homeomorphic but not diffeomorphic to the standard 7-sphere.

What do you think?

Note: If you have a contribution, then (by definition) it will be a paper worth reading so please do give a journal reference or hyperlink!

Edit: To echo Richard's comment, the emphasis here is really on short papers. However I don't want to give an arbitrary numerical bound, so just use good judgement...

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You should probably bound the length, cuz otherwise you could just pick your favorite paper of Ratner, Grothendieck, Thurston, et cetera and the importance blows everything else away. – Richard Kent Dec 1 '09 at 1:41
Or Gromov, "from whose sentences people have written theses" (as I have seen someone write somewhere) – Mariano Suárez-Alvarez Dec 1 '09 at 2:31
The award for the corresponding question for paper titles would have to go to "H = W". Meyers and Serrin, Proc. Nat. Acad, Sci. USA 51 (1964), 1055-6. – John D. Cook Jan 6 '10 at 2:49
It also depends on what you define a "paper". A number of fundamental results have been announced, and their proof has been sketched, in the C.R. Acad. Sci. - and all of them are four pages long. – Delio Mugnolo Nov 9 '13 at 14:48

The 1949 paper by R.C. Bose "A Note on Fisher's Inequality for Balanced Incomplete Block Designs" arguably gave birth to the linear algebra method in combinatorics which has since been used by many to solve highly non-trivial problems as discussed here: Linear Algebra Proofs in Combinatorics?

Here's a description of Bose and his work from the manuscript Linear Algebra Methods in Combinatorics by Babai and Frankl:

The affiliation listed on Bose’s paper is the Institute of Statistics, University of North Carolina. Before taking up residence in the U.S. in 1948, Bose worked at the Indian Statistical Institute in Calcutta. One of the most influential combinatorialists of the decades to come, Bose was forced to become a statistician by the lack of employment chances in mathematics in his native country. A pure mathematician hardly in disguise, he reared generations of combinatorialists. His students at Chapel Hill included D. K. Ray-Chaudhuri, a name that together with his student R. M. Wilson (so, may be a grandson of Bose?) will appear several dozen times on these pages for their far reaching extension of Bose’s method.

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Not sure how important, but certainly short.

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It's a disproof of a conjecture by no less than Euler! – David Roberts Apr 15 '15 at 2:33

I suppose the word "importance" in the equation can allow for some subjective input (some papers might be important to certain people, while to others not so important for their work).

This paper, entitled Finiteness of the number of compatibly-split subvarieties by Kumar and Mehta, is only 3 pages long:

http://arxiv.org/abs/0901.2098

For those who work with Frobenius splittings, it is an important result, one which was actually believed to be true for decades but not proven until 2009!

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Maybe the paper of R. Brauer and Fowler, K. A. (1955): "On groups of even order", Annals of Mathematic, Second Series 62: 565–583, ISSN 0003-486X, JSTOR 1970080, MR 0074414 deserves a mention since this is generally accepted as the point when it was realised the Classification of the Finite Simple Groups might be a feasible project.

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Pretty late to the party here but Kantorovich's "On the translocation of masses" from 1942 is two pages. It gave a radically new look on the Monge problem of optimal transportation and can be seen as the starting point of an immense body of work on optimal transport and distances in probability spaces.

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An algorithm for the machine calculation of complex Fourier series by Cooley and Tukey, which introduces the fast fourier transform.

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How about Galois's letter written on the eve of his death and published by Liouville 17 years later?

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I think we should draw the line somewhere when it comes to what constitutes a paper. Otherwise we will have Archimedes's sketch on a bit of slate while he was down the taverna with the lads... – Yemon Choi Oct 2 '14 at 17:04
+1 Maybe we should draw a line, but how can we not to mention the Galois's letter??? – TT_ Oct 7 '14 at 20:05

Erdős' 1947 paper Some remarks on the theory of graphs'', which is just 3 pages long, gives the lower bound $R(k,k)>2^{k/2}$ for the diagonal Ramsey numbers. It could have been a much shorter paper; he completes the proof of the lower bound before the end of the first page!

The paper is important not just for the bound, which (essentially) hasn't been improved in 65 years, but also for the method used; although this paper wasn't the first to use the probabilistic method, it is certainly the most influential early paper to have done so.

P. Erdős, Some remarks on the theory of graphs, Bull. Amer. Math. Soc. 53 (1947) 292-294

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It's not a paper, and it's not groundbreaking, but it's short!

A One-Sentence Proof That Every Prime $p\equiv 1\pmod 4$ Is a Sum of Two Squares D. Zagier The American Mathematical Monthly, Vol. 97, No. 2 (Feb., 1990), p. 144 http://www.jstor.org/pss/2323918

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That's a beautiful one indeed. And it also has lot of potential for the (obscurity of the idea)/(line count) competition :P – Mariano Suárez-Alvarez Jan 6 '10 at 3:39
And you can see that sentence for only $12 at JSTOR! – I. J. Kennedy May 17 '10 at 0:37 Save 12 bucks: The involution on a finite set$S = \{(x,y,z) \in \mathbb{N}^3 : x^2 +4yz = p \} $defined by: $(x,y,z) \mapsto \left\{ \begin{array}{cc} (x+2z,z,y-x-z) & \text{if } x < y-z \\ ( 2y-x, y, y-x+z ) & \text{if } y-z < x <2y \\ ( x-2y, x-y+z, y ) & \text{if } x > 2y \end{array} \right.$ has exactly one fixed point, so$|S|$is odd and the involution defined by$(x,y,z) \mapsto (x,z,y)$also has a fixed point. – Zavosh May 21 '10 at 11:46 One thing I've always wondered - is there any intuition behind the involution? – dvitek Sep 30 '10 at 4:16 +1 to Mariano and drvitek. It is hardly a memorable proof. That is, unless you have some special insight or photographic memory, you're not going to remember how that involution goes. I once wrote a crabby blog post about this proof, here: topologicalmusings.wordpress.com/2008/05/04/… – Todd Trimble Nov 7 '11 at 22:09 Here is my list (in no specific order): (*) A proof of Ehrenfeucht's conjecture about infinite systems of equations in free groups and semigroups by Victor Guba: V.S.Guba "Equivalence of infinite systems of equations in free groups and semigroups to finite subsystems", Mathematical notes of the Academy of Sciences of the USSR, September 1986, Volume 40, 3, pp 688-690. (*) A.A.Razborov, “Lower bounds on monotone complexity of the logical permanent”, Math. Notes USSR, 37:6 (1985), 485–493. As Laszlo Lovasz put it in his talk "The Work of A.A.Razborov" (can be easily found on the Internet): In an area where any step forward seemed almost hopeless (but which was at the same time a central area of theoretical computer science) his results meant that deep methods could be developed and to obtain strong lower bounds for algorithms was not impossible. (*) Isaac Newton "The mathematical principles of natural philosophy" - in this case the (finite) length of the work does not matter, since the importance is infinite :) - I think S.T. Yau's paper that proves the Calabi conjecture is a good example. It's 2 pages long(!) and it got him a Fields medal(along with other works, certainly). It also contains a lot of other new results (!!) - Golay's single page paper describing what is today known as Golay code, a perfect code of length 23. This is even used in NASA deep space missions, and is one of the only perfect codes which are not Hamming codes. - Already mentioned back in 2010: mathoverflow.net/a/18697/763 – Yemon Choi Sep 15 '14 at 15:13 Funny that Witt is not mentioned here. Indeed, his papers Theorie der quadratischen Formen in beliebigen Körpern (introducing Witt cancellation, Witt decomposition, the Hasse-Witt invariant, the Witt ring and in a little sidestep proving that every quadratic form in$\ge 5$variables over a$\mathfrak{p}$-adic field is isotropic) and Zyklische Körper und Algebren der Chrakteristik$p$vom Grad$p^n$(introducing Witt vectors, Artin-Schreier-Witt theory and determining the structure of complete discrete valuation rings) at 13 resp. 14 pages are among the longest he has ever published. But they both appeared in the remarkable volume 176 of Crelle's Journal, and giving their importance, I think they still make up a reasonable answer. - MR0011027 Chern, Shiing-shen A simple intrinsic proof of the Gauss-Bonnet formula for closed Riemannian manifolds. Ann. of Math. (2) 45, (1944). 747–752 Quoting from Andre Weil's review: In order to understand the true nature of the Euler-Poincaré characteristic of a (differentiable) manifold, one has to consider it as a topological invariant of a fibre-space invariantly attached to the manifold, namely, of the space of tangent unit-vectors (or "tangent sphere bundle'') to the manifold. It is therefore only natural that an intrinsic proof of the Gauss-Bonnet formula (which expresses the Euler-Poincaré characteristic as the integral of a differential form invariantly attached to the Riemannian structure) should involve the consideration of that fibre-space. This is how the author proceeds here; and his proof, as he states, is merely the simplest example of a general method in the differential-geometric study of fibre-spaces, which is developed in the paper reviewed below." The proof is truly intrinsic, as Chern did not use an isometric imbedding of a Riemannian manifold into an Euclidean space. And it is simple to follow. - I will vote for C.Fefferman's paper "The multiplier problem for the ball" http://mate.dm.uba.ar/~hafg/inter-u-2010/fefferman.pdf, which is only about 5 pages and he solved an open problem about multipliers, and he wrote this when he was only a teenager! - My vote is: • K.A. Perko, Jr., On the classification of knots, Proc. Amer. Math. Soc. 45 (1974), 262-266. This historical paper triumphantly concludes a century-old quest to tabulate prime knots with ten of fewer crossings. There are two pages of text explaining the methodology (covering linkage numbers), and three pages of tables. A widely accepted 19th century result of Little, that writhe of reduced diagrams of the same knot is the same, is falsified by the discovery of the Perko pair at the bottom of page 263. In my opinion this may be the most interesting mathematics mistake of all time. For more on this paper and on the fascinating story behind it, see Richard Elwes's lovely blog post, and what I wrote here. - I read all 30 previous answers, and then did "search" on this page with my browser, and to my surprise I did not find Picard's name. Picard's proof of the Picard Little Theorem certainly qualifies for this list. See, for example Littlewood's Miscellany, where he discusses the question, "Can a PhD thesis consist of one line?" Picard's one-line proof started an enormous body of literature in XX century, beginning with Nevanlinna theory and including Hyperbolic groups. To be sure, Picard's original paper (CR 88(1879)1024-7) is slightly longer than one line, but the proof itself (assuming the background that was well-known in 1879) is really one line, as reproduced in Littlewood:-) A slight generalization of this is called Picard's Great Theorem, the only theorem that I know, which has the word "Great" in its standard name:-) - About your last sentence: Theorema Egregium comes very close... – user5117 Jul 15 '13 at 17:31 Littlewood/Picard has not been mentioned in this thread, but it has appeared elsewhere on this site: tea.mathoverflow.net/discussion/946/shortest-phd-thesis and mathoverflow.net/questions/54775/… – Gerry Myerson Jul 15 '13 at 23:16 A. Karatsuba and Yu. Ofman (1962). "Multiplication of Many-Digital Numbers by Automatic Computers". Proceedings of the USSR Academy of Sciences 145: 293–294. Proved that multiplication of$n$-digit numbers could be done in less than quadratic time (thus disproving a conjecture by Kolmogorov) and provided the first divide-and-conquer algorithm for arithmetic. - J.-C. Yoccoz called Carl L. Siegel, Iteration of analytic functions, Ann. of Math. 43(2) (1942), 607–612. a "brief but historic article". In only 6 pages (including all necessary background) Siegel gave the ﬁrst positive solution to a small denominator problem. This had been a major unsolved issue for over 60 years, and was a big thorn in the side for Poincaré. Siegel's paper is also credited with inspiring Kolmogorov to start the circle of ideas that led to KAM Theory. Buff, Henriksen, and Hubbard did not hesitate in calling it “one of the landmark papers of the twentieth century.” Details - Robert Aumann's "Agreeing to Disagree" paper, at 3 pages of length, is one of the most important papers in its field. - -- -- I disagree. -- – Włodzimierz Holsztyński Sep 28 '14 at 18:36 What about Ribet's great Inventiones paper from the 70's$\textit{A modular construction of unramified }p\textit{-extensions of }\mathbf{Q}(\mu_p)$? I think it should be mentioned! - A favourite of mine is Kobayashi and Wu's 4 page Annals paper "On holomorphic sections of certain Hermitian vector bundles" where they introduce the Bochner-method, which is nowadays used everywhere in differential geometry as an easy and effective method of proving vanishing results. - Bochner method was introduced by Bochner in 1946-48 and used by numerous authors to prove vanishing theorems for cohomology groups of vector bundles ever since. This remark, of course, is not meant to diminish Kobayashi-Wu's 1970 paper. – Misha May 25 '13 at 18:37 Évariste Galois, "Mémoire sur les conditions de résolubilité des équations par radicaux". I believe it's about 18 pages, but the foundations of Galois theory are contained within the first few pages. - I'm surprised this hasn't been mentioned yet, but Rostislav Grigorchuk's 1980 paper in which he constructs the Grigorchuk group is just under two pages: On the Burnside problem on periodic groups, Funkts. Anal. Prilozen. 14, No 1 (1980) 53-54. At the time, no one realized the full significance of this group, but some of the more remarkable properties are proven in the paper. - Cooley and Tukey (re)invented the Fast Fourier Transform with a 5-page paper in Mathematics of Computation (1965). - Perelman's Proof of the soul conjecture of Cheeger and Gromoll.'' J. Differential Geom. 40 (1994), no. 1, 209–212, http://projecteuclid.org/DPubS?service=UI&version=1.0&verb=Display&handle=euclid.jdg/1214455292 is, at 3 pages (plus a paragraph of remarks), a favourite of mine, although it has some pretty tough competition here. - L. Euler Solutio problematis ad geometriam situs pertinentis, Commentarii academiae scientiarum Petropolitanae 8, 1741, pp. 128-140. was the famous Bridges of Königsberg paper. It was the beginning of both topology and graph theory. It is translated into English in Newman's "World of Mathematics" and in Biggs, Lloyd & Wilson's "Graph Theory 1736-1936". In Opera Omnia it is 10 pages long. - What about Atiyah's K-theory and Reality? I know it's not that short with its 20 pages, but if you see the paper, you notice that he didn't use his space very economically. He did provide the foundation of topological K-theory though. - Adams' review of this paper ends with The reviewer is conscious that the paper contains points of interest not mentioned above; he pleads that this is a paper of 19 pages which cannot be summarised adequately in less than 20, and urges topologists to read it.'' – Peter May Apr 11 '13 at 13:32 I think this is the shortest paper (1 page) with the most large title in combinatorics (24 words!): "Alexander Burstein's Lovely Combinatorial Proof of John Noonan's Beautiful Formula that the number of$n$-permutations that contain the Pattern$321$Exactly Once Equals$(3/n)(2n)!/((n-3)!(n+3)!)\$"

by Doron Zeilberger, http://arxiv.org/pdf/1110.4379 .

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Paul Cohen's paper "The independence of the continuum hypothesis" in which he introduced forcing. Six pages long (and another six in the second paper, a year later) that completely changed logic and set theory.

JSTOR access (may require a paywall)

While I'm at it, two more in set theory:

Kurt Goedel's proof of the consistency of the continuum hypothesis and the axiom of choice, a two pages long paper.