On the Lower Bounds of Ramsey Numbers of Knots
نویسندگان
چکیده
The Ramsey number is known for only a few specific knots and links, namely the Hopf link and the trefoil knot (although not published in periodicals). We establish the lower bound of all Ramsey numbers of any knot to be one greater than its stick number. 1 Background and Definitions The study of Ramsey numbers of knots can be found at the intersection of knot theory and graph theory. 1.1 Knot Theory Background A knot is a simple closed curve in <3, while a link is a set of disjoint knots. As shown in figure 1 the unknot(a), trefoil knot(b), figure-8 knot(c), unlink(d), and Hopf link(e) are examples of inequivalent links. Figure 1 Some simple knots Stick knots are knots composed of straight line segments intersecting only two at a time. The stick number, s(k), of a knot k, is the fewest number of sticks necessary to embed a knot in <3. Many stick numbers for knots are known (MM). For example, s(unknot) = 3, s(unlink) = 6, s(trefoil) = 6, and s(figure − 8) = 7. Illustrations of these are in Figure 2. Also, Calvo has classified all 8-stick knots(JC).
منابع مشابه
Zarankiewicz Numbers and Bipartite Ramsey Numbers
The Zarankiewicz number z(b; s) is the maximum size of a subgraph of Kb,b which does not contain Ks,s as a subgraph. The two-color bipartite Ramsey number b(s, t) is the smallest integer b such that any coloring of the edges of Kb,b with two colors contains a Ks,s in the rst color or a Kt,t in the second color.In this work, we design and exploit a computational method for bounding and computing...
متن کاملRamsey Numbers and Other Knot Invariants
We make use of a particular linear spatial embedding, the cyclic polytope, in an exploration of bounds on the Ramsey number of knots. Using arc presentations to simplify knotted cycles of this embedding, we examine the relationships between the Ramsey number, bridge number, crossing number, stick number and arc index of knots. In particular we show the Ramsey number is at least as large as the ...
متن کاملComputational lower limits on small Ramsey numbers
Computer-based attempts to construct lower bounds for small Ramsey numbers are discussed. A systematic review of cyclic Ramsey graphs is attempted. Many known lower bounds are reproduced. Several new bounds are reported. ar X iv :1 50 5. 07 18 6v 5 [ cs .D M ] 1 M ar 2 01 6
متن کاملConstructive lower bounds for Ramsey numbers from linear graphs
Giraud (1968) demonstrated a process for constructing cyclic Ramsey graph colourings, starting from a known cyclic ‘prototype’ colouring, adding edges of a single new colour, and producing a larger cyclic pattern. This paper describes an extension of that construction which allows any number of new colours to be introduced simultaneously, by using two multicolour prototypes, each of which is a ...
متن کاملNew lower bounds for two multicolor classical Ramsey numbers
We present an algorithm to find lower bounds for multicolor classical Ramsey numbers by using 2-normalized cyclic graphs of prime order, and use it to obtain new lower bounds for two multicolor classical Ramsey numbers: R(3, 3, 12) ≥ 182, R(3, 3, 13) ≥ 212.
متن کامل