Hypertranscendental function

A hypertranscendental function or transcendentally transcendental function is an analytic function which is not the solution of an algebraic differential equation with coefficients in Z (the integers) and with algebraic initial conditions. All hypertranscendental functions are transcendental functions.

History

The term 'transcendentally transcendental' was introduced by Eliakim H. Moore in 1896; the term 'hypertranscendental' was introduced by D. D. Morduhai-Boltovskoi in 1914.

Definition

One standard definition (there are slight variants) defines solutions of differential equations of the form

$F\left(x,y,y',\cdots ,y^{(n)}\right)=0$,

where $F$ is a polynomial with constant coefficients, as algebraically transcendental or differentially algebraic. Transcendental functions which are not algebraically transcendental are transcendentally transcendental. Hölder's theorem shows that the gamma function is in this category.

Hypertranscendental functions usually arise as the solutions to functional equations, for example the gamma function.

Examples

Known hypertranscendental functions

• The zeta functions of algebraic number fields, in particular, the Riemann zeta function
• The gamma function (cf. Hölder's theorem)

Functions which are not hypertranscendental

• All algebraic functions, in particular polynomials.
• The exponential function, logarithm, and the trigonometric and hyperbolic functions.
• All generalized hypergeometric functions, including special cases such as Bessel functions.

See also

• Hypertranscendental number

References

• Loxton,J.H., Poorten,A.J. van der, "A class of hypertranscendental functions", Aequationes Mathematicae, Periodical volume 16
• Mahler,K., "Arithmetische Eigenschaften einer Klasse transzendental-transzendenter Funktionen", Math. Z. 32 (1930) 545-585.
• Morduhaĭ-Boltovskoĭ, D. (1949), "On hypertranscendental functions and hypertranscendental numbers", Doklady Akad. Nauk SSSR (N.S.) (in Russian), 64: 21–24, MR 0028347