The (lower) domination number of a graph is the minimum size of a dominating set of vertices in , i.e., the size of a minimum dominating set. This is equivalent to the smallest size of a minimal dominating set since every minimum dominating set is also minimal. The domination number is also equal to smallest exponent in a domination polynomial. For example, in the Petersen graph illustrated above, the set is a minimum dominating set, so .
The upper domination number may be similarly defined as the maximum size of a minimal dominating set of vertices in (Burger et al. 1997, Mynhardt and Roux 2020).
The (lower) irredundance number , lower domination number , lower independence number , upper independence number , upper domination number , and upper irredundance number satsify the chain of inequalities
(1)
|
(Burger et al. 1997).
The domination number should not be confused with the domatic number, which is the maximum size of a domatic partition in a graph.
There are several variations of the domination number originating from variations of the underlying dominating set, the most prevalent being the total domination number (which is the minimum size of a total dominating set).
The complete graphs (each vertex is adjacent to every other), star graphs (the central vertex is adjacent to all leaves), and the wheel graph (the central vertex is adjacent to all rim vertices) all have domination number 1 by construction.
The domination number satisfies
(2)
|
where is the vertex count of a graph and is its maximum vertex degree.
For a graph with vertex count and no isolated vertices (i.e., minimum vertex degree ),
(3)
|
(Ore 1962, Bujtás and Klavar 2014). Stricter results are known when , 3, etc. (cf. Bujtás and Klavar 2014).
MacGillivray and Seyffarth (1996) showed that planar graphs with graph diameter 2 have domination number at most three and planar graphs with graph diameter 3 have domination number at most ten. Goddard and Henning (2002) showed in fact there is a unique diameter-2 planar graph with domination three (here called the Goddard-Henning graph), with all other such graphs having domination number at most 2. According to Goddard and Henning (2002), it is not known if the bound for planar diameter-3 graphs is sharp, but MacGillivray and Seyffarth (1996) gave an example of such of graph with domination number 6.
The total domination number and ordinary domination number satisfy
(4)
|
(Henning and Yeo 2013, p. 17).
Östergård et al. (2015) give bounds on the domination numbers of Kneser graphs, together with a number of exact values for smaller cases.
Precomputed dominating sets for many named graphs can be obtained in the Wolfram Language using GraphData[graph, "DominationNumber"].
The following table summarizes values of the domination number for various special classes of graphs.
graph | OEIS | , , ... |
Andrásfai graph | A158799 | 1, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, ... |
Apollonian network | A000000 | 1, 1, 3, 4, 7, 16, ... |
antiprism graph | A057354 | 2, 2, 2, 3, 3, 4, 4, 4, 5, 5, 6, 6, 6, 7, ... |
barbell graph | A007395 | 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, ... |
book graph | A007395 | 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, ... |
centipede graph | A000027 | 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, ... |
cocktail party graph | A007395 | 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, ... |
complete bipartite graph | A007395 | 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, ... |
complete graph | A000012 | 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, ... |
complete tripartite graph | A000000 | 1 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, ... |
-crossed prism graph | A052928 | X, 2, 4, 4, 6, 6, 8, 8, 10, 10, 12, 12, ... |
crown graph | A007395 | 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, ... |
cube-connected cycle graph | A000000 | 6, 16, 46, 96, 224, 512, ... |
cycle graph | A002264 | X, X, 1, 2, 2, 2, 3, 3, 3, 4, 4, 4, 5, 5, 5, ... |
empty graph | A000027 | 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, ... |
folded cube graph | A271520 | 1, 1, 2, 4, 6, 8, 16, 32, ... |
grid graph | A104519 | 2, 3, 4, 7, 10, 12, 16, 20, 24, ... |
grid graph | A269706 | 1, 2, 6, 15, 25, 42, ... |
gear graph | A000000 | X, X, 2, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8, 9, 9, 10, 10, ... |
halved cube graph | A000000 | 1, 1, 1, 2, 2, 2, 4, 7, 12, ... |
helm graph | A000027 | X, X, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, ... |
hypercube graph | A000983 | 1, 2, 2, 4, 7, 12, 16, 32, ... |
Keller graph | A000000 | 4, 4, 4, 4, ... |
-king graph | A075561 | 1, 1, 1, 4, 4, 4, 9, 9, 9, 16, 16, 16, 25, 25, 25, 36, ... |
-knight graph | A006075 | 1, 4, 4, 4, 5, 8, 10, 12, 14, 16, 21, 24, 28, 32, 36, ... |
ladder graph | A004526 | 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8, 9, 9, ... |
ladder rung graph | A000027 | 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, ... |
Möbius ladder | A004525 | X, X, 2, 3, 3, 3, 4, 5, 5, 5, 6, 7, 7, 7, 8, 9, 9, 9, ... |
Mycielski graph | A000000 | 1, 1, 2, 3, 4, 5, 6, 7, 8, ... |
odd graph | A000000 | 1, 1, 3, 7, 26, 66, ... |
pan graph | A002264 | X, X, 1, 2, 2, 2, 3, 3, 3, 4, 4, 4, 5, 5, 5, 6, 6, 6, 7, ... |
path graph | A002264 | X, 1, 1, 2, 2, 2, 3, 3, 3, 4, 4, 4, 5, 5, 5, 6, 6, 6, 7, ... |
prism graph | A004524 | X, X, 2, 2, 3, 4, 4, 4, 5, 6, 6, 6, 7, 8, 8, 8, 9, 10, ... |
-queen graph | A075458 | 1, 1, 1, 2, 3, 3, 4, 5, 5, 5, 5, 6, 7, 8, 9, 9, 9, 9, 10, ... |
Sierpiński carpet graph | A000000 | 3, 18, 130, ... |
Sierpiński gasket graph | A000000 | 1, 2, 3, 9, 27, ... |
star graph | A000012 | 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, ... |
sun graph | A004526 | X, X, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8, 9, 9, 10, ... |
sunlet graph | A000000 | |
tetrahedral Johnson graph | A000000 | X, X, X, X, X, 2, 4, 5, 7, 8, ... |
torus grid graph | A000000 | |
transposition graph | A000000 | 1, 1, 2, 4, 15, ... |
triangular graph | A004526 | 2, 3, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8, 9, 9, ... |
triangular honeycomb acute knight graph | A000000 | 1, 3, 3, 3, 3, 6, 9, 9, 9, 10, 15, 18, 18, 18, ... |
triangular honeycomb obtuse knight graph | A251534 | X, X, X, 4, 5, 5, 6, 6, 9, 11, 12, 14, 15, 16, 18, 19, ... |
triangular honeycomb queen graph | A000000 | 1, 1, 2, 2, 3, 3, 3, 4, 4, 5, ... |
triangular honeycomb rook graph | A000027 | 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, ... |
web graph | A000027 | X, X, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, ... |
wheel graph | A000012 | 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, ... |
Closed forms are summarized in the following table.