Green index in semigroups: generators, presentations, and automatic structures
Green index in semigroups: generators, presentations, and automatic structures
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半群中的绿色索引:生成器、演示和自动结构
DOI:
10.1007/s00233-012-9406-2
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发表时间:
2012
期刊:
影响因子:
0.7
通讯作者:
Cain A
中科院分区:
文献类型:
--
作者:
Cain A
The Green index of a subsemigroup T of a semigroup S is given by counting strong orbits in the complement S∖ T under the natural actions of T on S via right and left multiplication. This partitions the complement S∖ T into T-relative-classes, in the sense of Wallace, and with each such class there is a naturally associated group called the relative Schützenberger group. If the Rees index| S∖ T| is finite, T also has finite Green index in S. If S is a group and T a subgroup then T has finite Green index in S if and only if it has finite group index in S. Thus Green index provides a common generalisation of Rees index and group index. We prove a rewriting theorem which shows how generating sets for S may be used to obtain generating sets for T and the Schützenberger groups, and vice versa. We also give a method for constructing a presentation for S from presentations of T and the Schützenberger groups. These results are then used to show that several important properties are preserved when passing to finite Green index subsemigroups or extensions, including: finite generation, solubility of the word problem, growth type, automaticity (for subsemigroups), finite presentability (for extensions) and finite Malcev presentability (in the case of group-embeddable semigroups).
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DOI:
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发表时间:
1996
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影响因子:
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作者:
C. Campbell;E. Robertson;N. Ruškuc;R. Thomas
通讯作者:
R. Thomas
DOI:
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发表时间:
2006
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作者:
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DOI:
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发表时间:
1998
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作者:
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通讯作者:
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1978
期刊:
Canadian mathematical bulletin
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作者:
A. Jura
通讯作者:
A. Jura
DOI:
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发表时间:
1963
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影响因子:
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作者:
A. D. Wallace
通讯作者:
A. D. Wallace