Hilbert's twelfth problem

Es handelt sich um meinen liebsten Jugendtraum, nämlich um den Nachweis, dass die Abel ’schen Gleichungen mit Quadratwurzeln rationaler Zahlen durch die Transformations- Gleichungen elliptischer Functionen mit singularen Moduln grade so erschöpft werden, wie die ganzzahligen Abel’schen Gleichungen durch die Kreisteilungsgleichungen.

Kronecker's Jugendtraum or Hilbert's twelfth problem, of the 23 mathematical Hilbert problems, is the extension of the Kronecker–Weber theorem on abelian extensions of the rational numbers, to any base number field. That is, it asks for analogues of the roots of unity, as complex numbers that are particular values of the exponential function; the requirement is that such numbers should generate a whole family of further number fields that are analogues of the cyclotomic fields and their subfields.

The classical theory of complex multiplication, now often known as the Kronecker Jugendtraum, does this for the case of any imaginary quadratic field, by using modular functions and elliptic functions chosen with a particular period lattice related to the field in question. Goro Shimura extended this to CM fields. The general case is still open as of 2014^[update]. Leopold Kronecker described the complex multiplication issue as his liebster Jugendtraum or “dearest dream of his youth”.

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