properties of discriminant in algebraic number field
Theorem 1. Let and be elements of the algebraic number field of degree (http://planetmath.org/NumberField) . If they satisfy the equations
where all coefficients are rational numbers
, then the http://planetmath.org/node/12060discriminants
are via the equation
As a special case one obtains the
Theorem 2. If
(1) |
are the canonical forms of the elements in , then
where is a Vandermonde determinant thushaving the product form
(2) |
where are the algebraic conjugates of .
Since the (2) is also the polynomial discriminant of the irreducible minimal polynomial of , the numbers are inequal. It follows the
Theorem 3. When (1) are the canonical forms of the numbers , one has
The powers of the primitive element (http://planetmath.org/SimpleFieldExtension) form a basis (http://planetmath.org/Basis) of the field extension (see the canonical form of element of number field). By the theorem 3 we may write the
Theorem 4. The numbers of are linearly independent over if and only if .
Theorem 5. . Here, the the discriminant is the discriminant of the algebraic number (http://planetmath.org/DiscriminantOfAlgebraicNumber) .