We prove that a connected graph of diameter at least 4 and of girth 7 or more (in particular, a tree) can be exactly reconstructed from metric balls of radius 2 of all its vertices. On the other hand, there exist graphs of diameter 3 and of girth 6 which are not reconstructible. This new graph theory problem is motivated by reconstruction of chemical compounds. © 2007 Published by Elsevier B.V.

A proper vertex coloring of a graph G is equitable if the sizes of color classes differ by at most one. The equitable chromatic threshold χeq(G) of G is the smallest integer m such that G is equitably n-colorable for all n ≥ m. We show that for planar graphs G with minimum degree at least two, χeq(G) ≤ 4 if the girth of G is at least 10, and χeq(G) ≤ 3 if the girth of G is at least 14.

Tian and Meng in [Y. Tian and J. Meng, c  -Optimally half vertex transitive graphs with regularity , Information Processing Letters 109 (2009) 683-686] shown that a connected half vertex transitive graph with regularity and girth is cyclically optimal. In this paper, we show that a connected half vertex transitive graph G is super cyclically edge-connected if minimum degree k k   6 g G   ...

This article studies the girth and cogirth problems for connected matroids. The problem of finding the cogirth of a graphic matroid has been intensively studied, but studies on the equivalent problem for a linear matroid or a general matroid have been rarely reported. Based on the duality and connectivity of a matroid, we prove properties associated with the girth and cogirth of a matroid whose...

We have been investigating the cryptographical properties of infinite families of simple graphs of large girth with the special colouring of vertices during the last 10 years. Such families can be used for the development of cryptographical algorithms (on symmetric or public key modes) and turbocodes in error correction theory. Only few families of simple graphs of large unbounded girth and arb...

In this paper, the concept of the broken diagonal pair in the chess-like square board is used to define some well-structured block designs whose incidence matrices can be considered as the parity-check matrices of some high rate cycle codes with girth 12. Interestingly, the constructed regular cycle codes with row-weights t, 3 ≤ t ≤ 20, t 6= 7, 15, 16, have the best lengths among the known regu...

If a nonsymmetric P-polynomial association scheme, or equivalently. a distanceregular digraph, has diameter d and girth g. then d = g or d = g 1, by Damerell’s theorem. The dual of this theorem was proved by Leonard. In this paper, we prove that the diameter of a nonsymmetric Pand Q-polynomial association scheme is one less than its girth and its cogirth. We also give a structure theorem for a ...

A quasi-cyclic (QC) low-density parity-check (LDPC) code can be viewed as the protograph code with circulant permutation matrices. In this paper, we find all the subgraph patterns of protographs of QC LDPC codes having inevitable cycles of length 2i, i = 6, 7, 8, 9, 10, i.e., the cycles existing regardless of the shift values of circulants. It is also derived that if the girth of the protograph...

Tal Amasay1,∗ and Andrew Karduna2 1Department of Sport and Exercise Sciences, School of Human Performance and Leisure Sciences Barry University, 11300 NE 2nd Ave., Miami Shores, FL 33161, USA 2Department of Human Physiology, University of Oregon, Eugene, OR 97405, USA OCCUPATIONAL APPLICATIONS This study found that dental hygienists are exposed to higher shoulder elevation angles when treating ...

The oriented chromatic number o(H) of an oriented graph H is defined to be the minimum order of an oriented graph H ' such that H has a homomorphism to H' . If each graph in a class ~ has a homomorphism to the same H' , then H ' is ~-universal. Let ~k denote the class of orientations of planar graphs with girth at least k. Clearly, ~3 ~ ~4 ~ ~5... We discuss the existence of ~k-universal graphs...