Higher composition laws and applications
Higher composition laws and applications
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高等成分定律及应用
DOI:
10.4171/022-2/13
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发表时间:
2006
影响因子:
0.9
通讯作者:
M. Bhargava
中科院分区:
文献类型:
--
作者:
M. Bhargava
In 1801 Gauss laid down a remarkable lawof composition on integral binary quadratic
forms. This discovery, known as Gauss composition, not only had a profound influence on
elementary number theory but also laid the foundations for ideal theory and modern algebraic
number theory. Even today, Gauss composition remains one of the best ways of understanding
ideal class groups of quadratic fields.
The question arises as to whether there might exist similar laws of composition on other spaces
of forms that could shed light on the structure of other algebraic number rings and fields. In this
article we present several such higher analogues of Gauss composition, and we describe how
each of these composition laws can be interpreted in terms of ideal classes in appropriate rings of
algebraic integers. We also discuss several applications of these composition laws, including the
resolution of a critical case of the Cohen�Lenstra�Martinet heuristics, and a solution of the longstanding
problem of counting the number of quartic and quintic fields of bounded discriminant.
In addition, we describe the mysterious relationship between these various composition laws
and the exceptional Lie groups. Finally, we discuss prospects for future work and conclude with
several open questions.