In number theory an ideal number is an algebraic integer which represents an ideal in the ring of integers of a number field; the idea was developed by Ernst Kummer, and led to Richard Dedekind's definition of ideals for rings. An ideal in the ring of integers of an algebraic number field is principal if it consists of multiples of a single element of the ring, and nonprincipal otherwise. By the principal ideal theorem any nonprincipal ideal becomes principal when extended to an ideal of the Hilbert class field. This means that there is an element of the ring of integers of the Hilbert class field, which is an ideal number, such that the original nonprincipal ideal is equal to the collection of all multiples of this ideal number by elements of this ring of integers that lie in the original field's ring of integers.
Famous quotes containing the words ideal and/or number:
“It is well worth the efforts of a lifetime to have attained knowledge which justifies an attack on the root of all evil—viz. the deadly atheism which asserts that because forms of evil have always existed in society, therefore they must always exist; and that the attainment of a high ideal is a hopeless chimera.”
—Elizabeth Blackwell (1821–1910)
“My tendency to nervousness in my younger days, in view of the fact of a number of near relatives on both my father’s and mother’s side of the house having become insane, gave some serious uneasiness. I made up my mind to overcome it.... In the cross-examination of witnesses before a crowded court-house ... I soon found I could control myself even in the worst of testing cases. Finally, in battle.”
—Rutherford Birchard Hayes (1822–1893)