Algebraic elements and algebraic extensions

An element of an R-algebra is algebraic over R if it is the root of a nonzero polynomial. An R-algebra is algebraic over R if and only if all its elements are algebraic over R. The main result in this file proves transitivity of algebraicity: a tower of algebraic field extensions is algebraic.


is_algebraic

An element of an R-algebra is algebraic over R if it is the root of a nonzero polynomial.

subalgebra.is_algebraic

A subalgebra is algebraic if all its elements are algebraic.

algebra.is_algebraic

An algebra is algebraic if all its elements are algebraic.

subalgebra.is_algebraic_iff

A subalgebra is algebraic if and only if it is algebraic an algebra.

algebra.is_algebraic_iff

An algebra is algebraic if and only if it is algebraic as a subalgebra.

is_integral.is_algebraic

An integral element of an algebra is algebraic.

is_algebraic_iff_is_integral

An element of an algebra over a field is algebraic if and only if it is integral.

algebra.is_algebraic_trans

If L is an algebraic field extension of K and A is an algebraic algebra over L, then A is algebraic over K.