122,108 research outputs found
On efficient total domination
An efficiently total dominating set of a graph G is a subset of its vertices such that each vertex of G is adjacent to exactly one vertex of the subset. If there is such a subset, then G is an efficiently total dominatable graph (G is etd). We show that the corresponding etd decision problem is NP-complete on (1,2)-colorable chordal graphs and on planar bipartite graphs of maximum degree 3 and obtain polynomial solvability on T_3-free chordal graphs, implying polynomial solvability on interval graphs and circular arc graphs
Efficient total domination in digraphs
We generalize the concept of efficient total domination from graphs to digraphs. An efficiently total dominating set X of a digraph D is a vertex subset such that every vertex of D has exactly one predecessor in X . Not every digraph has an efficiently total dominating set. We study graphs that permit an orientation having such a set and give complexity results and characterizations concerning this question. Furthermore, we study the computational complexity of the (weighted) efficient total domination problem for several digraph classes. In particular we deal with most of the common generalizations of tournaments, like locally semicomplete and arc-locally semicomplete digraphs
Efficient domination in knights graphs
The influence of a vertex set S ⊆V(G) is I(S) = Σv∈S(1 + deg(v)) = Σv∈S |N[v]|, which is the total amount of domination done by the vertices in S. The efficient domination number F(G) of a graph G is equal to the maximum influence of a packing, that is, F(G) is the maximum number of vertices one can dominate under the restriction that no vertex gets dominated more than once.
In this paper, we consider the efficient domination number of some finite and infinite knights chessboard graphs
A Linear Kernel for Planar Total Dominating Set
A total dominating set of a graph is a subset such
that every vertex in is adjacent to some vertex in . Finding a total
dominating set of minimum size is NP-hard on planar graphs and W[2]-complete on
general graphs when parameterized by the solution size. By the meta-theorem of
Bodlaender et al. [J. ACM, 2016], there exists a linear kernel for Total
Dominating Set on graphs of bounded genus. Nevertheless, it is not clear how
such a kernel can be effectively constructed, and how to obtain explicit
reduction rules with reasonably small constants. Following the approach of
Alber et al. [J. ACM, 2004], we provide an explicit kernel for Total Dominating
Set on planar graphs with at most vertices, where is the size of the
solution. This result complements several known constructive linear kernels on
planar graphs for other domination problems such as Dominating Set, Edge
Dominating Set, Efficient Dominating Set, Connected Dominating Set, or Red-Blue
Dominating Set.Comment: 33 pages, 13 figure
Generating cosmological perturbations with mass variations
We study the possibility that large scale cosmological perturbations have
been generated during the domination and decay of a massive particle species
whose mass depends on the expectation value of a light scalar field. We discuss
the constraints that must be imposed on the field in order to remain light and
on the annihilation cross section and decay rate of the massive particles in
order for the mechanism to be efficient. We compute the resulting curvature
perturbations after the mass domination, recovering the results of Dvali,
Gruzinov, and Zaldarriaga in the limit of total domination. By comparing the
amplitude of perturbations generated by the mass domination to those originally
present from inflation, we conclude that this mechanism can be the primary
source of perturbations only if inflation does not rely on slow-roll
conditions.Comment: 8 pages. Proceeding of the workshop: `The Density Perturbation in the
Universe', Demokritos Center, Athens, Grece, June 200
Partitioning the vertex set of to make an efficient open domination graph
A graph is an efficient open domination graph if there exists a subset of
vertices whose open neighborhoods partition its vertex set. We characterize
those graphs for which the Cartesian product is an efficient
open domination graph when is a complete graph of order at least 3 or a
complete bipartite graph. The characterization is based on the existence of a
certain type of weak partition of . For the class of trees when is
complete of order at least 3, the characterization is constructive. In
addition, a special type of efficient open domination graph is characterized
among Cartesian products when is a 5-cycle or a 4-cycle.Comment: 16 pages, 2 figure
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