We construct infinitely many hyperbolic links with x-distance far from the set of (possibly, splittable) alternating links in the concordance class of every link. A sensitive result is given for the concordance class of every (possibly, split) alternating link. Our proof uses an estimate of the τ -distance by an Alexander invariant and the topological imitation theory, both established earlier by the author.
Alternation number and τ -alternation numberIn this paper, links are always oriented links in the oriented 3-sphere S 3 and a knot is regarded as a link of one component. An alternating link is a link with an alternating diagram, a link diagram such that an over-crossing and an under-crossing appear alternatively along every knot diagram component. Let A be the set of (possibly, splittable) alternating links. After the solution of the Tait flype conjecture on alternating links by W.W. Menasco and M.B. Thistlethwaite in [16], it became an important question to ask how a non-alternating link is "close to" or "far from" the set A under a suitable metric. The x-distance (or Gordian distance) d x (L, L ) between links L and L with the same number of components is the minimal number of cross-changes transforming a diagram of L into a diagram of L . A zero-linking twist of an oriented link L is an operation on links to obtain a link L from L by a twist along a trivial knot O such that L ∩ O = ∅ and the linking number Link(L, O ) = 0, and the τ -distance d τ (L, L ) between links L and L with the same number of components is the minimal number of zero-linking twists transforming L into L (cf. [12]). For links L, L with different numbers of components, we define d τ (L, L ) = d(L, L ) = +∞. Since the crossing change is a zero-linking twist and every link diagram is transformed into a diagram of a trivial link by crossing changes, we have 0 d τ (L, L ) d x (L, L ) < +∞ for all links L, L with the same number of components. The x-distance and the τ -distance are metric functions on the set of links with r components for every r 1. An estimate of d τ (L, L ) was done in [12] in terms of local link signatures and