Prime knots and tangles
Prime knots and tangles
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主要结和缠结
DOI:
10.1090/s0002-9947-1981-0621991-2
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发表时间:
1981
影响因子:
1.3
通讯作者:
W. Lickorish
中科院分区:
文献类型:
--
作者:
W. Lickorish
A study is made of a method of proving that a classical knot or link is prime. The method consists of identifying together the boundaries of two prime tangles. Examples and ways of constructing prime tangles are explored. Introduction. This paper explores the idea of the prime tangle that was briefly introduced in [KL]. It is here shown that summing together two prime tangles always produces a prime knot or link. Here a tangle is just two arcs spanning a 3-ball, and such a tangle is prime if it contains no knotted ball pair and its arcs cannot be separated by a disc. A few prototype examples of prime tangles are given (Figure 2), together with ways of using them to create infinitely many more (Theorem 3). Then, usage of the prime tangle idea becomes a powerful machine, nicely complementing other methods, in the production of prime knots and links. Finally it is shown (Theorem 5) that the idea of the prime tangle has a very natural interpretation in terms of double branched covers. The paper should be interpreted as being in either the P.L. or smooth category. With the exception of the section on double branched covers, all the methods used are the straightforward (innermost disc) techniques of the elementary theory of 3-manifolds. None of the proofs is difficult; the paper aims for significance rather than sophistication. Indeed various possible generalizations of the prime tangle have not been developed (e.g. n arcs, for n > 2, or arcs in a ball-with-holes meeting each boundary component in four points) in order to avoid unnecessary complication. The author wishes to record his gratitude to the University of California at Santa Barbara for providing opportunity, facilities and inspiration for the writing of this