On Thompson's finiteness theorem. (Q1770452)
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scientific article; zbMATH DE number 2153320
| Language | Label | Description | Also known as |
|---|---|---|---|
| English | On Thompson's finiteness theorem. |
scientific article; zbMATH DE number 2153320 |
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On Thompson's finiteness theorem. (English)
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7 April 2005
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The author gives an alternative (constructive) proof of Thompson's finiteness theorem for a family of congruence subgroups of the modular group. If \(G\) is a subgroup of \(\text{PSL}(2,\mathbb{R})\) commensurable with the modular group, then Thompson's theorem says that its Euler characteristic is given in terms of the orders of non-conjugate classes of elliptic elements, its genus and the parabolic class number.
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modular group
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congruence subgroups
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Thompson theorem
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elliptic elements
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genera
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parabolic class numbers
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