# .

Hilbert's seventh problem is one of David Hilbert's list of open mathematical problems posed in 1900. It concerns the irrationality and transcendence of certain numbers (Irrationalität und Transzendenz bestimmter Zahlen).

Statement of the problem

In an isosceles triangle, if the ratio of the base angle to the angle at the vertex is algebraic but not rational, is then the ratio between base and side always transcendental?
Is a^b always transcendental, for algebraic $$a \not\in \{0,1\}$$ and irrational algebraic b?

Solution

The second question was answered in the affirmative by Aleksandr Gelfond in 1934, and refined by Theodor Schneider in 1935. This result is known as Gelfond's theorem or the Gelfond–Schneider theorem. (The restriction to irrational b is important, since it is easy to see that a^b is algebraic for algebraic a and rational b.)

From the point of view of generalisations, this is the case

$$b \ln{\alpha} + \ln{\beta} = 0$$

of the general linear form in logarithms which was attacked by Gelfond and then solved by Alan Baker. It is called the Gelfond conjecture or Baker's theorem. Baker was rewarded as a Fields Medal winner in 1970 because of this.

The first question is a consequence of the second question.

Hilbert number or Gelfond–Schneider constant

Hilbert's problems : 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

References

Tijdeman, Robert (1976). "On the Gel'fond–Baker method and its applications". In Felix E. Browder. Mathematical Developments Arising from Hilbert Problems. Proceedings of Symposia in Pure Mathematics. XXVIII.1. American Mathematical Society. pp. 241–268. ISBN 0-8218-1428-1. Zbl 0341.10026.
Manin, Yu. I.; Panchishkin, A. A. (2007). Introduction to Modern Number Theory. Encyclopaedia of Mathematical Sciences 49 (Second ed.). p. 61. ISBN 978-3-540-20364-3. ISSN 0938-0396. Zbl 1079.11002.

English translation of Hilbert's original address