| Project/Area Number |
13640053
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Algebra
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| Research Institution | TOBA NATIONAL COLLEGE OF MARITIME TECHNOLOGY |
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Principal Investigator |
OKUYAMA Takashi TOBA NATIONAL COLLEGE OF MARITIME TECHNOLOGY ASSOCIATE PROFESSOR, 助教授 (20177190)
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| Co-Investigator(Kenkyū-buntansha) |
SANAMI Manabu TOBA NATIONAL COLLEGE OF MARITIME TECHNOLOGY LECTURER, 講師 (10226029)
NASHIRO Hiroaki TOBA NATIONAL COLLEGE OF MARITIME TECHNOLOGY PROFESSOR, 教授 (40043252)
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| Project Period (FY) |
2001 – 2002
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| Project Status |
Completed (Fiscal Year 2002)
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| Budget Amount *help |
¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 2002: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2001: ¥800,000 (Direct Cost: ¥800,000)
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| Keywords | Purifiable Subgroups / Quasi-Purifiable Subgroups / p-overhang set / The maximal torsion subgroup / Torsion-Free subgroup / T-High Subgroup / Height-Matrices / Torsion-Free Rank / 準純粋包をもつ部分群 / 純粋包 / p-overhang set / 準純粋包 / empty-p-overhang set部分群 / 最大ねじれ部分群 |
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| Research Abstract |
In an arbitrary abelian group G, a subgroup A of G is said to be purifiable in G if there exists a pure subgroup H of G containing A which is minimal among the pure subgroups of G that contain A. Such a subgroup H is called a pure hull of A. In general, not all subgroups are purifiable. Now we can pose the following problem: Which subgroup is purifiable in a given group?
We started this project with the problem. In this project, we considered only torsion-free subgroups. Finally, we obtained the following results.
(1) We characterized torsion-free finite rank purifiable subgroups in give groups.
(2) We proved that all pure hulls of purifiable torsion-free subgroups are isomorphic.
We used the result (1) to study the splitting problem. The splitting problem is to characterize mixed groups which are a direct sum of the maximal torsion and torsion-free subgroup. We obtained a necessary and sufficient condition for abelian groups of finite torsion-free rank to be splitting.
A subgroup A of an a
… More
belian group G is said to be quasi-purifiable in G if there exists a pure subgroup K of G containing A such that A is almost-dense in H and H/A is torsion. Such a subgroup K is called a quasi-pure hull of A in G. We can also pose the following problem.
Which subgroup is quasi-purifiable in a given group?
In this project, for the above problem, we characterized torsion-free rank-one quasi-purifiable subgroups in given groups. We used this result to show how to calculate the height-matrices of straight elements. Height-matrices are important. For example, it is well-known that countable mixed groups H and K of torsion-free rank 1 are isomorphic if and only if T(H) is isomorphic to T(K) and the height-matrices of H and K are equivalent.
If a subgroup A of a group G is quasi-purifiable in G, then there exists a maximal quasi-pure hull of A in G. So we might use the concept of maximal quasi-pure hulls to study the groups whose maximal torsion-subgroups are torsion-complete. These groups whose maximal torsion subgroups are torsion-complete include direct products of cyclic p-groups. This study could be next. Less
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