**Transcendence theory** is a branch of

number theory that investigates

transcendental numbers, in both qualitative and quantitative ways.

## Transcendence

The

fundamental theorem of algebra tells us that if we have a non-zero

polynomial with integer coefficients then that polynomial will have a root in the

complex numbers. That is, for any polynomial

*P* with integer coefficients there will be a complex number α such that

*P*(α) = 0. Transcendence theory is concerned with the converse question, given a complex number α, is there a polynomial

*P* with integer coefficients such that

*P*(α) = 0? If no such polynomial exists then the number is called transcendental.

More generally the theory deals with

algebraic independence of numbers. A set of numbers is called algebraically independent over a field

*k* if there is no non-zero polynomial

*P* in

*n* variables with coefficients in

*k* such that

*P*(α<sub>1</sub>,α<sub>2</sub>,…,α<sub>n</sub>) = 0. So working out if a given number is transcendental is really a special case of algebraic independence where our set consists of just one number.

A related but broader notion than "algebraic" is whether there is a

closed-form expression for a number, including exponentials and logarithms as well as algebraic operations. There are various definitions of "closed-form", and questions about closed-form can often be reduced to questions about transcendence.

## History

### Approximation by rational......

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