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class number problem

In mathematics, the Gauss class number problem (for imaginary quadratic fields), as usually understood, is to provide for each n\geq 1 a complete list of imaginary quadratic fields \mathbb{Q}(\sqrt{d}) (for negative integers d ) having class number n . It is named after Carl Friedrich Gauss. It can also be stated in terms of discriminants. There are related questions for real quadratic fields and for the behavior as d \to -\infty . The difficulty is in effective computation of bounds: for a given discriminant, it is easy to compute the class number, and there are several ineffective lower bounds on class number (meaning that they involve a constant that is not computed), but effective bounds (and explicit proofs of completeness of lists) are harder.

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Article summary

In mathematics, the Gauss class number problem (for imaginary quadratic fields), as usually understood, is to provide for each n\geq 1 a complete list of imaginary quadratic fields \mathbb{Q}(\sqrt{d}) (for negative integers d ) having class number n . It is named after Carl Friedrich Gauss. It can also be stated in terms of discriminants. There are related questions for real quadratic fields and for the behavior as d \to -\infty . The difficulty is in effective computation of bounds: for a given discriminant, it is easy to compute the class number, and there are several ineffective lower bounds on class number (meaning that they involve a constant that is not computed), but effective bounds (and explicit proofs of completeness of lists) are harder.

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