Siegel G-function

{{Short description|Class of functions in transcendental number theory}}

{{about|Siegel G-functions|the general functions introduced by Cornelius Meijer|Meijer G-function}}

In mathematics, the Siegel G-functions are a class of functions in transcendental number theory introduced by C. L. Siegel. They satisfy a linear differential equation with polynomial coefficients, and the coefficients of their power series expansion lie in a fixed algebraic number field and have heights of at most exponential growth.

Definition

A Siegel G-function is a function given by an infinite power series

: $f(z)=\sum_{n=0}^\infty a_n z^n$

where the coefficients a_n all belong to the same algebraic number field, K, and with the following two properties.

f is the solution to a linear differential equation with coefficients that are polynomials in z. More precisely, there is a differential operator $L\in K[z,d_z], L\neq 0$ , such that $L.f=0$ ;
the projective height of the first n coefficients is O(cⁿ) for some fixed constant c > 0. That is, the denominators of $a_0,\dots,a_n$ (the denominator of an algebraic number $x$ is the smallest positive integer $m$ such $mx$ is an algebraic integer) are $\leq c^n$ and the algebraic conjugates of $a_n$ have their absolute value bounded by $c^n$ .

The second condition means the coefficients of f grow no faster than a geometric series. Indeed, the functions can be considered as generalisations of geometric series, whence the name G-function, just as E-functions are generalisations of the exponential function.

References

{{eom|id=g/g110010|title=G-function|first=F. |last=Beukers}}
C. L. Siegel, "Über einige Anwendungen diophantischer Approximationen", Ges. Abhandlungen, I, Springer (1966)

Category:Analytic number theory

Category:Algebraic number theory

Category:Ordinary differential equations

Category:Transcendental numbers

Category:Analytic functions