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E. F. Combarro 《Algebra and Logic》2002,41(5):285-294
We study automorphism groups of two important predicates in computability theory: the predicate Wy and the graph of a universal partially computable function. It is shown that all automorphisms of the predicates in question are computable. The actions of the automorphism groups on some index sets are examined, and we establish a number of results on the structure of these. We also look into homomorphisms of the two predicates. In this case the situation changes: all homomorphisms of the universal function are computable, but in each Turing degree, homomorphisms of Wy exist. 相似文献
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We prove that each computable Boolean algebra has a computable presentation in which for every computable family of automorphisms the set of atoms moved by at least one of its members is finite. This implies that each computable atomic Boolean algebra has a computable presentation in which its every computable family of automorphisms is finite. The priority argument is not used in the proof. 相似文献
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E. W. Madison 《Acta Mathematica Hungarica》2003,98(1-2):31-37
The Baire category theorem for compact Hausdorff spaces is used to show that any recursive completion ℬϕof the countable atomless Boolean algebra ℬ is ℬrecursively closed." Also, a theorem of R.D. Anderson on the simplicity of
Aut(ℬ) is used to show that uncountably many automorphisms of ℬ extend to ℬϕ.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
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本文提出应用小参数法 ,探讨 Markov链中相邻两次更新时刻内稀疏事件的概率估计问题 .建立了三种最重要的具有更新时间的概率模型 .通过小参数的引入和对概率式的幂展开 ,进而推证出幂渐近展开系数的模型估算法 .论证了无偏估计的重要定理 ,给出了概率估计式和无偏估计精度 .亦将许多算法扩展到Markov链的任意状态空间 相似文献
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The paper is devoted to an application of a general local method of studying the Fredholmness of nonlocal bounded linear operators to Banach algebras of singular integral operators with piecewise continuous coefficients and discrete subexponential groups of piecewise smooth shifts acting topologically freely on composed contours. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献