Smale's problems is a list of eighteenunsolved problems in mathematics proposed bySteve Smale in 1998[1] and republished in 1999.[2] Smale composed this list in reply to a request fromVladimir Arnold, then vice-president of theInternational Mathematical Union, who asked several mathematicians to propose a list of problems for the 21st century. Arnold's inspiration came from the list ofHilbert's problems that had been published at the beginning of the 20th century.
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Problem | Brief explanation | Status | Year Solved |
---|---|---|---|
1st | Riemann hypothesis: Thereal part of every non-trivialzero of theRiemann zeta function is 1/2. (see alsoHilbert's eighth problem) | Unresolved. | – |
2nd | Poincaré conjecture: Everysimply connected, closed 3-manifold ishomeomorphic to the3-sphere. | Resolved. Result: Yes, Proved byGrigori Perelman usingRicci flow.[3][4][5] | 2003 |
3rd | P versus NP problem: For all problems for which analgorithm canverify a given solution quickly (that is, inpolynomial time), can an algorithm alsofind that solution quickly? | Unresolved. | – |
4th | Shub–Smale tau-conjecture on theinteger zeros of apolynomial of one variable[6][7] | Unresolved. | – |
5th | Can one decide if aDiophantine equationƒ(x, y) = 0 (inputƒ ∈ [u, v ]) has an integer solution, (x, y), in time (2s)c for some universal constant c? That is, can the problem be decided inexponential time? | Unresolved. | – |
6th | Is the number of relative equilibria (central configurations) finite in then-body problem ofcelestial mechanics, for any choice of positivereal numbersm1, ..., mn as the masses? | Partially resolved. Proved for almost all systems of five bodies by A. Albouy and V. Kaloshin in 2012.[8] | 2012 |
7th | Algorithm for finding set of such that thefunction: is minimized for a distribution ofN points on a2-sphere. This is related to theThomson problem. | Unresolved. | – |
8th | Extend themathematical model ofgeneral equilibrium theory to include price adjustments | Gjerstad (2013)[9] extends the deterministic model of price adjustment by Hahn and Negishi (1962)[10] to astochastic model and shows that when the stochastic model is linearized around the equilibrium the result is the autoregressive price adjustment model used in applied econometrics. He then tests the model with price adjustment data from a general equilibrium experiment. The model performs well in a general equilibrium experiment with two commodities. Lindgren (2022)[11] provides a dynamic programming model for general equilibrium with price adjustments, where price dynamics are given by a Hamilton-Jacobi-Bellman partial differerential equation. Good Lyapunov stability conditions are provided as well. | |
9th | Thelinear programming problem: Find astrongly-polynomial time algorithm which for givenmatrixA ∈ Rm×n andb ∈ Rm decides whether there existsx ∈ Rn withAx ≥ b. | Unresolved. | – |
10th | Pugh's closing lemma (higher order of smoothness) | Partially resolved. Proved for Hamiltoniandiffeomorphisms of closed surfaces by M. Asaoka and K. Irie in 2016.[12] | 2016 |
11th | Is one-dimensional dynamics generally hyperbolic? (a) Can acomplex polynomialT be approximated by one of the samedegree with the property that every critical point tends to a periodic sink under iteration? (b) Can a smooth mapT : [0,1] → [0,1] beC r approximated by one which is hyperbolic, for allr > 1? | (a) Unresolved, even in the simplest parameter space of polynomials, theMandelbrot set. (b) Resolved. Proved by Kozlovski, Shen and van Strien.[13] | 2007 |
12th | For aclosed manifold and any let be thetopological group ofdiffeomorphisms of onto itself. Given arbitrary, is it possible to approximate it arbitrary well by such that it commutes only with its iterates? In other words, is the subset of all diffeomorphisms whosecentralizers are trivial dense in? | Partially resolved. Solved in theC1topology by Christian Bonatti, Sylvain Crovisier andAmie Wilkinson[14] in 2009. Still open in theC r topology forr > 1. | 2009 |
13th | Hilbert's 16th problem: Describe relative positions of ovals originating from arealalgebraic curve and aslimit cycles of a polynomialvector field on the plane. | Unresolved, even for algebraic curves of degree 8. | – |
14th | Do the properties of theLorenz attractor exhibit that of a strange attractor? | Resolved. Result: Yes, solved byWarwick Tucker using acomputer-assisted proof combined with normal form techniques.[15] | 2002 |
15th | Do theNavier–Stokes equations inR3 always have aunique smooth solution that extends for all time? | Unresolved. | – |
16th | Jacobian conjecture: If theJacobian determinant ofF is a non-zero constant andk hascharacteristic 0, thenF has aninverse functionG : kN → kN, andG isregular (in the sense that its components are polynomials). | Unresolved. | – |
17th | Solvingpolynomial equations inpolynomial time in the average case | Resolved. C. Beltrán and L. M. Pardo found two uniform probabilistic algorithms (averageLas Vegas algorithm) for Smale's 17th problem[16][17][18] F. Cucker andP. Bürgisser made thesmoothed analysis of a probabilistic algorithmà la Beltrán-Pardo and then exhibited a deterministic algorithm running in time.[19] Finally,P. Lairez found an alternative method to de-randomize the algorithmà la Beltrán-Pardo and thus found a deterministic algorithm which runs in average polynomial time.[20] All these works follow Shub and Smale's foundational work (the "Bezout series") started in[21] | 2008-2016 |
18th | Limits ofintelligence (it talks about the fundamental problems of intelligence and learning, both from the human and machine side)[22] | Some recent authors have claimed results, including the unlimited nature of human intelligence[23] and limitations on neural-network-based artificial intelligence[24] | – |
In later versions, Smale also listed three additional problems, "that don't seem important enough to merit a place on our main list, but it would still be nice to solve them:"[25][26]