A non-zero polynomial with coefficients in a field is irreducible if when written as the product of two polynomials, one of or is a constant (and necessarily non-zero) polynomial. Equivalently, a polynomial is irreducible if the ideal it generates is a maximal ideal of the polynomial ring .
In other words, a polynomial is irreducible if it is an irreducible element of as an integral domain.
Notice that under this definition, the zero polynomial is not considered to be irreducible. An alternative definition, which applies to the case of coefficients in a commutative ring , is that a polynomial is irreducible if, whenever divides , either divides or divides . Under this definition, a polynomial is irreducible if it generates a prime ideal in , and the zero polynomial is irreducible if is an integral domain.
If is a field extension of and is algebraic over (i.e., the smallest subextension containing , , is finite-dimensional over ), then the -algebra map has a non-trivial kernel which is a maximal ideal, which being principal is generated by an irreducible polynomial . The unique monic polynomial generator is called the irreducible polynomial of .
Over a unique factorization domain eisenstein's criterion? determines irreducibility
Last revised on June 20, 2019 at 10:34:54. See the history of this page for a list of all contributions to it.