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In mathematics, complex multiplication is the theory of elliptic curves ''E'' that have an endomorphism ring larger than the integers; and also the theory in higher dimensions of abelian varieties ''A'' having ''enough'' endomorphisms in a certain precise sense (it roughly means that the action on the tangent space at the identity element of ''A'' is a direct sum of one-dimensional modules). Put another way, it contains the theory of elliptic functions with extra symmetries, such as are visible when the period lattice is the Gaussian integer lattice or Eisenstein integer lattice. It has an aspect belonging to the theory of special functions, because such elliptic functions, or abelian functions of several complex variables, are then 'very special' functions satisfying extra identities and taking explicitly calculable special values at particular points. It has also turned out to be a central theme in algebraic number theory, allowing some features of the theory of cyclotomic fields to be carried over to wider areas of application. David Hilbert is said to have remarked that the theory of complex multiplication of elliptic curves was not only the most beautiful part of mathematics but of all science. ==Example of the imaginary quadratic field extension== Consider an imaginary quadratic extension field , which provides the typical example of complex multiplication. For the two periods of an elliptic function it is called to be of complex multiplication if there is an algebraic relation between and for all in . Conversely, Kronecker conjectured that every abelian extension of would be obtained by the (roots of the) equation of a suitable elliptic curve with complex multiplication, known as the ''Kronecker Jugendtraum'' and ''Hilbert's twelfth problem''. An example of an elliptic curve with complex multiplication is : where Z() is the Gaussian integer ring, and θ is any non-zero complex number. Any such complex torus has the Gaussian integers as endomorphism ring. It is known that the corresponding curves can all be written as : having an order 4 automorphism sending : in line with the action of ''i'' on the Weierstrass elliptic functions. More generally, consider the group of lattice L on the complex plane generated by . Then we define the Weierstrass function with a variable in as follows: : where : : Let be the derivative of . Then we obtain the isomorphism: : which means the 1 to 1 correspondence between the complex torus group and the elliptic curve : in the complex plane. This means that the ring of analytic automorphic group of i.e., the ring of automorphisms of , turn out to be isomorphic to the (subring of) integer rings of . In particular, assume and consider as an ideal of then is agreed with the integer rings . Rewrite and , then : This means that the J-invariants of belong to the algebraic numbers of if has complex multiplication. 抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「complex multiplication」の詳細全文を読む スポンサード リンク
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