Inverse Galois problem over Q
Problem. Prove or disprove: for every finite group there is a finite Galois extension with
Equivalently, for every finite group there is a monic irreducible polynomial whose splitting field over has Galois group isomorphic to . The two forms agree because every finite Galois extension of is the splitting field of the minimal polynomial of a primitive element.
A stronger variant is the regular inverse Galois problem: for every finite group , find a Galois extension with and . By Hilbert's irreducibility theorem, a regular realization specializes at infinitely many to Galois extensions of with group . So a positive answer to the regular problem implies a positive answer here. The problem here is the one over as stated above.
Background
The question goes back to Hilbert's 1892 irreducibility theorem, which he used to realize the symmetric and alternating groups over . Emmy Noether proposed a geometric approach in 1918. If the fixed field of a permutation action is purely transcendental, then has a regular realization. Swan showed that this fails for the cyclic group of order , so Noether's approach cannot work for all groups [2].
The most productive general method is rigidity. It uses rational rigid tuples of conjugacy classes to produce -covers of defined over , branched over three or more points, hence regular realizations [2, 3]. Thompson used it to realize the Monster group [4]. Other approaches use embedding problems, which proceed by lifting a realization of a quotient of , and arithmetic geometry, including rational points on moduli spaces of covers and Galois representations attached to modular forms [1, 2].
References
- O. Wittenberg, "Around the inverse Galois problem", in Number Theory Informed by Computation, IAS/Park City Math. Ser. 29, AMS (2025), 291–322. doi:10.1090/pcms/029/08
- G. Malle and B. H. Matzat, Inverse Galois Theory, 2nd ed., Springer Monographs in Math., Springer (2018). doi:10.1007/978-3-662-55420-3
- H. Völklein, Groups as Galois Groups: An Introduction, Cambridge Stud. Adv. Math. 53, Cambridge Univ. Press (1996). doi:10.1017/CBO9780511471117
- J. G. Thompson, "Some finite groups which appear as , where ", J. Algebra 89 (1984), 437–499. doi:10.1016/0021-8693(84)90228-X
- I. R. Šafarevič, "Construction of fields of algebraic numbers with given solvable Galois group", Amer. Math. Soc. Transl. (2) 4 (1956), 185–237. doi:10.1090/trans2/004/08
- J. Neukirch, A. Schmidt and K. Wingberg, Cohomology of Number Fields, 2nd ed., Grundlehren Math. Wiss. 323, Springer (2008), Chapter IX. doi:10.1007/978-3-540-37889-1
- X. Huang, B. Jackson, K.-H. Lee, B. Poonen, R. Pries and S. Zhang, "The Mathieu group is a Galois group over ", preprint (2026). arXiv:2608.08538
- Wikipedia, Inverse Galois problem.
Source: Wikipedia
Progress summary
The general question remains open, while August claims cover one long-standing exceptional case and all groups in degree 24, without independent verification.
The inverse Galois problem asks whether every finite group occurs as the Galois group of an extension of . Posed in the early nineteenth century, it remains unresolved in general.
Known results
- Hilbert realized and over .
- Scholz and Reichardt (1937) realized every odd -group.
- Shafarevich (1954; proof corrected in 1989) realized every finite solvable group.
- By 1989, of the sporadic simple groups were realized over .
August 2026 claimed advances
On August 11, 2026, Huang, Jackson, Lee, Poonen, Pries, and Zhang were reported to have constructed a degree- polynomial with Galois group , completing the sporadic cases; the claim is unverified. On August 8, 2026, the IGP24 competition announced realizations for all approximately degree- groups, also without independent verification. Neither claim resolves arbitrary finite groups.
Current status (as of September 2026): Realizability over is settled for all finite solvable groups and many nonsolvable families; recent claims cover and degree- groups, but the general problem remains open and those claims are unverified.
Solutions 0
No solutions have been posted yet.