Hostname: page-component-78c5997874-mlc7c Total loading time: 0 Render date: 2024-11-16T19:10:14.298Z Has data issue: false hasContentIssue false

A necessary condition on minimal cube numberings

Published online by Cambridge University Press:  14 July 2016

L. H. Harper*
Affiliation:
The Rockefeller University, New York

Extract

Let G = (V, E) be a graph with N vertices and A a set of N real numbers. Then a one-to-one mapping ϕ: V → A is called a numbering of G. The elements of A will always be assumed ordered a1a2 ≦ … ≦ aN. In [3] and [7] it was shown how to construct numberings of the n-cube, in fact all numberings, which minimize Σe ∈ E Δe where ∆e = |ϕ(v) – ϕ(w)| and e is the edge between vertices v and w. A variant problem of considerable interest is to do the same for Σe ∈ Ee)2. It is conjectured that when A = {1,2, …,2n} the natural numbering is the unique minimizer of Σe ∈ Ee)2 for every n, but this has so far resisted all efforts. Theorem 1 in the following is the result of attempts to get weaker results, namely to thin out the ranks of those numberings which could possibly minimize Σe ∈ Ee)2. The second problem posed and solved in this paper is a generalization of the results in [3], where the n-cube becomes the n-torus.

Type
Short Communications
Copyright
Copyright © Sheffield: Applied Probability Trust 

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

[1] Bernstein, A. J., Steiglitz, K. and Hopcroft, J. E. Encoding of analog signals for a binary symmetric channel. To be published in IEEE Trans. Information Theory. Google Scholar
[2] Golomb, S. W. (1965) Data processing and its relation to the communication of deep-space experiments. Progress in Radio Science 1960–1963, Vol. VIII.Google Scholar
[3] Harper, L. H. (1964) Optimal assignments of numbers to vertices. J. Soc. Indust. Appl. Math. 12, 131135.Google Scholar
[4] Harper, L. H. (1967) Optimal numberings and isoperimetric problems on graphs. To be published in J. Combinatorial Theory. CrossRefGoogle Scholar
[5] Harper, L. H. (1967) Minimal numberings and isoperimetric problems on cubes. Actes des Journées d'Etudes sur la théorie des GraphesICC, Dunod.Google Scholar
[6] Lindsey, J. H. Ii, (1964) Assignments of numbers to vertices. Amer. Math. Monthly 71, 508516.CrossRefGoogle Scholar
[7] Steiglitz, K. and Bernstein, A. J. (1965) Optimal binary coding of ordered numbers. J. Soc. Indust. Appl. Math. 13, 441443.CrossRefGoogle Scholar