An Improved Nordhaus–Gaddum-Type Theorem for 2-Rainbow Independent Domination Number

For a graph G, its k-rainbow independent domination number, written as γrik(G), is defined as the cardinality of a minimum set consisting of k vertex-disjoint independent sets V1,V2,…,Vk such that every vertex in V0=V(G)\(∪i=1kVi) has a neighbor in Vi for all i∈{1,2,…,k}. This domination invariant was proposed by Kraner Šumenjak, Rall and Tepeh (in Applied Mathematics and Computation 333(15), 2018: 353–361), which aims to compute the independent domination number of G□Kk (the generalized prism) via studying the problem of integer labeling on G. They proved a Nordhaus–Gaddum-type theorem: 5≤γri2(G)+γri2(G¯)≤n+3 for any n-order graph G with n≥3, in which G¯ denotes the complement of G. This work improves their result and shows that if G≇C5, then 5≤γri2(G)+γri2(G¯)≤n+2.

Polynomial invariants of virtual doodles and virtual knots

In this study, we describe a method of making an invariant of virtual knots defined in terms of an integer labeling of the flat virtual knot diagram. We give an invariant of flat virtual knots and virtual doodles modifying the previous invariant.

An invariant of virtual knots using flat virtual knot diagrams

In this paper, we describe a method of making an invariant of virtual knots that is defined in terms of an integer labeling of the flat virtual knot diagram. We give an invariant of flat virtual knots using the invariant above. Moreover, we derive a relation of two invariants.

Polynomial invariants of flat virtual links using invariants of virtual links

In this paper, we describe a method of making a polynomial invariant of flat virtual knots in terms of an integer labeling of the flat virtual knot diagram and an invariant of virtual links. We show that the polynomial is sometimes useful to detect non-invertibility and also to determine the virtual crossing number of a given flat virtual knot.

AN AFFINE INDEX POLYNOMIAL INVARIANT OF VIRTUAL KNOTS

This paper describes a polynomial invariant of virtual knots that is defined in terms of an integer labeling of the virtual knot diagram. This labeling is seen to derive from an essentially unique structure of affine flat biquandle for flat virtual diagrams. The invariant is discussed in detail with many examples, including its relation to previous invariants of this type and we show how to construct Vassiliev invariants from the same data.

Largest cliques in connected supermagic graphs

International audience A graph $G=(V,E)$ is said to be $\textit{magic}$ if there exists an integer labeling $f: V \cup E \to [1, |V \cup E|]$ such that $f(x)+f(y)+f(xy)$ is constant for all edges $xy \in E$. Enomoto, Masuda and Nakamigawa proved that there are magic graphs of order at most $3n^2+o(n^2)$ which contain a complete graph of order $n$. Bounds on Sidon sets show that the order of such a graph is at least $n^2+o(n^2)$. We close the gap between those two bounds by showing that, for any given graph $H$ of order $n$, there are connected magic graphs of order $n^2+o(n^2)$ containing $H$ as an induced subgraph. Moreover it can be required that the graph admits a supermagic labelling $f$, which satisfies the additional condition $f(V)=[1,|V|]$.