We propose a characterization of provability in BI’s Pointer Logic (PL) that is based on semantic structures called resource graphs. This logic has been defined for reasoning about mutable data structures and results about models and verification have been already provided. Here, we define resource graphs that capture PL models by considering heaps as resources and by using a labelling process....

The 1–2–3 Conjecture, raised by Karoński, Łuczak and Thomason, states that almost every graph G admits a proper 3-labelling, i.e., labelling of the edges with 1, 2, 3 such no two adjacent vertices are incident to same sum labels. Another interpretation this conjecture, may be attributed Chartrand et al., is can turned into locally irregular multigraph M, having degree, replacing each its at mos...

A mapping from the vertex set of a graph G = (V,E) into an interval of integers {0, . . . , k} is an L(2, 1)-labelling of G of span k if any two adjacent vertices are mapped onto integers that are at least 2 apart, and every two vertices with a common neighbour are mapped onto distinct integers. It is known that for any fixed k ≥ 4, deciding the existence of such a labelling is an NP-complete p...

We present a deterministic, log-space algorithm that solves st-connectivity in undirected graphs. The previous bound on the space complexity of undirected st-connectivity was log(·) obtained by Armoni, Ta-Shma, Wigderson and Zhou [ATSWZ00]. As undirected st-connectivity is complete for the class of problems solvable by symmetric, non-deterministic, log-space computations (the class SL), this al...

Let G =( V, E) be a graph. A bijectionf: V+{ 1,2,. ., 1 VI} IS called a prime labelling if for each e = {u, u} in E, we have GCD(f(u),f(u))= 1. A graph admits a prime labelling is called a prime graph. Around ten years ago, Roger Entringer conjectured that every tree is prime. So far, this conjecture is still unsolved. In this paper, we show that the conjecture is true for trees of order up to ...

we study the set of all determinants of adjacency matrices of graphs with a given number of vertices. using brendan mckay's data base of small graphs, determinants of graphs with at most $9$ vertices are computed so that the number of non-isomorphic graphs with given vertices whose determinants are all equal to a number is exhibited in a table. using an idea of m. newman, it is proved that if $...

In structural pattern recognition, given a set of graphs, the computation of a Generalized Median Graph is a well known problem. Some methods approach the problem by assuming a relation between the Generalized Median Graph and the Common Labelling problem. However, this relation has still not been formally proved. In this paper, we analyse such relation between both problems. The main result pr...

A subgraph $H$ of a graph $G$ is isometric if the distances between vertices in coincide with corresponding $G$. We show that for any integer $n\ge 1$, there on $3^{n+O(\log^2 n)}$ contains copies all $n$-vertex graphs. Our main tool new type distance labelling scheme, whose study might be independent interest.

In this paper some new type of odd graceful graphs are investigated. We prove that the graph obtained by joining a cycle C8 with some star graphs S1,r keeping one vertex and three vertices gap between pair of vertices of the cycle admits odd graceful labelling. We also prove that the graph obtained by joining a cycle C12 with some star graphs S1,r keeping two, three and five vertices gap betwee...