scholarly journals Chromatic Classes of 2-Connected (n,n+4)-Graphs with Exactly Three Triangles and at Least Two Induced 4-Cycles

2011 ◽  
Vol 2011 ◽  
pp. 1-15
Author(s):  
G. C. Lau ◽  
Y. H. Peng

For a graph G, let P(G,λ) be its chromatic polynomial. Two graphs G and H are chromatically equivalent, denoted G∼H, if P(G,λ)=P(H,λ). A graph G is chromatically unique if P(H,λ)=P(G,λ) implies that H≅G. In this paper, we determine all chromatic equivalence classes of 2-connected (n,n+4)-graphs with exactly three triangles and at least two induced 4-cycles. As a byproduct of these, we obtain various new families of χ-equivalent graphs and χ-unique graphs.

1997 ◽  
Vol 172 (1-3) ◽  
pp. 103-114 ◽  
Author(s):  
Yee-Hock Peng ◽  
C.H.C. Little ◽  
K.L. Teo ◽  
H. Wang

2001 ◽  
Vol 232 (1-3) ◽  
pp. 175-183 ◽  
Author(s):  
Behnaz Omoomi ◽  
Yee-Hock Peng

Author(s):  
Valeriano Aiello ◽  
Arnaud Brothier ◽  
Roberto Conti

Abstract Following a procedure due to Jones, using suitably normalized elements in a Temperley–Lieb–Jones (planar) algebra, we introduce a 3-parametric family of unitary representations of the Thompson’s group $F$ equipped with canonical (vacuum) vectors and study some of their properties. In particular, we discuss the behavior at infinity of their matrix coefficients, thus showing that these representations do not contain any finite-type component. We then focus on a particular representation known to be quasi-regular and irreducible and show that it is inequivalent to itself once composed with a classical automorphism of $F$. This allows us to distinguish three equivalence classes in our family. Finally, we investigate a family of stabilizer subgroups of $F$ indexed by subfactor Jones indices that are described in terms of the chromatic polynomial. In contrast to the 1st non-trivial index value for which the corresponding subgroup is isomorphic to the Brown–Thompson’s group $F_3$, we show that when the index is large enough, this subgroup is always trivial.


2020 ◽  
Vol 12 (1) ◽  
Author(s):  
Jördis-Ann Schüler ◽  
Steffen Rechner ◽  
Matthias Müller-Hannemann

AbstractAn important task in cheminformatics is to test whether two molecules are equivalent with respect to their 2D structure. Mathematically, this amounts to solving the graph isomorphism problem for labelled graphs. In this paper, we present an approach which exploits chemical properties and the local neighbourhood of atoms to define highly distinctive node labels. These characteristic labels are the key for clever partitioning molecules into molecule equivalence classes and an effective equivalence test. Based on extensive computational experiments, we show that our algorithm is significantly faster than existing implementations within , and . We provide our Java implementation as an easy-to-use, open-source package (via GitHub) which is compatible with . It fully supports the distinction of different isotopes and molecules with radicals.


1989 ◽  
Vol 12 (3) ◽  
pp. 317-356
Author(s):  
David C. Rine

Partitioning and allocating of software components are two important parts of software design in distributed software engineering. This paper presents two general algorithms that can, to a limited extent, be used as tools to assist in partitioning software components represented as objects in a distributed software design environment. One algorithm produces a partition (equivalence classes) of the objects, and a second algorithm allows a minimum amount of redundancy. Only binary relationships of actions (use or non-use) are considered in this paper.


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