In mathematics, the Hilbert–Smith conjecture is concerned with the transformation groups of manifolds; and in particular with the limitations on topological groups G that can act effectively (faithfully) on a (topological) manifold M. Restricting to G which are locally compact and have a continuous, faithful group action on M, it states that G must be a Lie group.
Because of known structural results on G, it is enough to deal with the case where G is the additive group Zp of p-adic integers, for some prime number p. An equivalent form of the conjecture is that Zp has no faithful group action on a topological manifold.
The naming of the conjecture is for David Hilbert, and the American topologist Paul A. Smith. It is considered by some to be a better formulation of Hilbert's fifth problem, than the characterisation in the category of topological groups of the Lie groups often cited as a solution.
- Smith, Paul A. (1941), "Periodic and nearly periodic transformations", in Wilder, R.; Ayres, W, Lectures in Topology, Ann Arbor, MI: University of Michigan Press, pp. 159–190
- Chu, Hsin (1973), "On the embedding problem and the Hilbert-Smith conjecture", in Beck, Anatole, Recent Advances in Topological Dynamics, Lecture Notes in Mathematics 318, Springer-Verlag, pp. 78–85
- Repovš, Dušan; Ščepin, Evgenij V. (June 1997), "A proof of the Hilbert-Smith conjecture for actions by Lipschitz maps", Mathematische Annalen 308 (2): 361–364