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Lindemann-Weierstrass theorem

In mathematics, the Lindemann-Weierstrass theorem states that if α1,...,αn are algebraic numbers which are linearly independent over the rational numbers, then e^{\alpha_1} \cdots e^{\alpha_n} are algebraically independent over the algebraic numbers; in other words the set {e^{\alpha_1} \cdots e^{\alpha_n}} has transcendence degree n over \Bbb{Q}. An equivalent formulation of the theorem is that if α1,...,αn are distinct algebraic numbers then e^{\alpha_1} \cdots e^{\alpha_n} are linearly independent over the algebraic numbers.

The theorem is named for Ferdinand von Lindemann, who proved the particular result that π is transcendental, and Karl Weierstraß.

Transcendence of e and π

The transcendence of e and π are direct corollaries of this theorem. Suppose α is a nonzero algebraic number; then {α} is a linearly independent set over the rationals, and therefore {eα} has transcendence degree one over the rationals; or in other words eα is transcendental. Using the other formulation we can argue that if {0, α} is a set of distinct algebraic numbers, then the set {e0, eα} = {1, eα} is linearly independent over the algebraic numbers, and so eα is immediately seen to be transcendental. In particular, e1 = e is transcendental. Also, if β = eiα is transcendental, so are the real and imaginary parts of β, Re(β) = (β + β−1)/2 and Im(β) = (β − β−1)/2i, and hence cos(α) = Re(β) and sin(α) = Im(β) are also. Therefore, if π were algebraic, cos(π) = −1 and sin(π) = 0 would be transcendental, which proves by contradiction π is not algebraic, and hence is transcendental.

p-adic conjecture

The p-adic Lindemann-Weierstrass conjecture is that this conjecture is also true for a p-adic analog: if α1,...,αn are a set of algebraic numbers linearly independent over the rationals such that | αi | p < 1 / p for some prime p, then the p-adic exponentials e^{\alpha_1} \cdots e^{\alpha_n} are algebraically independent transcendentals.

01-04-2007 01:30:44
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