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Chromatic Invariant
المؤلف: Biggs, N. L
المصدر: Algebraic Graph Theory, 2nd ed. Cambridge, England: Cambridge University Press
الجزء والصفحة: ...
24-3-2022
1413
The chromatic invariant of a connected graph is the number of spanning trees of that have internal activity 1 and external activity 0.
For graphs other than the singleton graph (for which ), it is also given by
where is the vertex count and is the chromatic polynomial of .
A connected graph is separable iff and is a series-parallel graph iff (Biggs 1993, p. 109).
Unless otherwise stated, hydrogen atoms are usually ignored in the computation of such indices as organic chemists usually do when they write a benzene ring as a hexagon (Devillers and Balaban 1999, p. 25).
Special cases are summarized in the following table (Biggs 1993, p. 110).
graph | OEIS | , , ... |
Andrásfai graph | A280333 | 1, 1, 12, 815, 157762, ... |
antiprism graph | A294152 | X, X, 11, 38, 112, 309, 828, 2190, 5759, ... |
Apollonian network | A000000 | 2, 16, 8192, ... |
black bishop graph | A295170 | 1, 1, 0, 8, 3528, 18475776, ... |
cocktail party graph | A295166 | 2, 1, 11, 362, 21234, 1965624, 264398280, ... |
complete bipartite graph | A048144 | 1, 1, 5, 73, 2069, 95401, 6487445, 610093513, ... |
complete tripartite graph | A182553 | 1, 11, 1243, 490043, 463370491, ... |
complete graph | A000142 | 1, 1, 1, 2, 6, 24, 120, 720, 5040, 40320, ... |
-crossed prism graph | A295168 | X, 11, 85, 521, 2869, 15017, 76717, 387425, ... |
crown graph | A295171 | 1, 11, 328, 16369, 1181276, ... |
cube-connected cycle graph | A000000 | X, X, 2816, ... |
empty graph | A000000 | 1, 2, , 4, , 6, , 8, , 10, ... |
Fibonacci cube graph | A295927 | 1, 0, 0, 1, 36, 58432, ... |
folded cube graph | A295172 | X, 1, 2, 73, 1872172, ... |
gear graph | A000027 | X, X, 2, 3, 4, 5, 6, 7, 8, 9 ... |
grid graph | A182517 | 1, 1, 3, 72, ... |
grid graph | A295173 | 1, 11, 156284551, ... |
halved cube graph | A295174 | X, 1, 1, 2, 362, 1784062800, ... |
Hanoi graph | A295175 | 1, 64, 1073741824, ... |
hypercube graph | A295176 | 1, 1, 11, 48253, ... |
Keller graph | A000000 | 4, 1872172, ... |
king graph | A295177 | 1, 2, 48, 31328, 473555616, ... |
knight graph | A295178 | 1, 4, -1, 78, 1306725, ... |
Möbius ladder | A000325 | X, X, 5, 12, 27, 58, 121, 248, 503, 1014, ... |
Mycielski graph | A000000 | 1, 1, 1, 238, ... |
odd graph | A000000 | 1, 1, 36, ... |
permutation star graph | A000000 | 1, 1, 1, 87837, ... |
prism graph | A000295 | X, X, 4, 11, 26, 57, 120, 247, 502, 1013, ... |
queen graph | A295187 | 1, 2, 1308, 1238775828, ... |
rook complement graph | A295186 | 1, 0, 98, 787211620, ... |
rook graph | A295184 | X, 1, 98, ... |
Sierpiński sieve graph | A295189 | 1, 1, 27, 20346417, ... |
Sierpiński tetrahedron graph | A000000 | 2, 176, ... |
sun graph | A000142 | X, X, 1, 2, 6, 24, 120, 720, 5040, 40320, 362880, ... |
torus grid graph | A295191 | X, X, 98, 48253, 121790284, ... |
transposition graph | A000000 | 1, 1, 5, ... |
triangular graph | A295192 | X, 1, 1, 11, 3444, 32396796, ... |
triangular grid graph | A295190 | 1, 1, 1, 5, 97, 6739, 1611097, 1295101469, ... |
triangular honeycomb obtuse knight graph | A295194 | 1, , 6, 0, 0, 11687, 100231463, ... |
triangular honeycomb queen graph | A295195 | 1, 1, 11, 3714, 39103200, ... |
wheel graph | A000027 | X, X, X, 2, 3, 4, 5, 6, 7, 8, 9, 10, ... |
white bishop graph | A295217 | 1, 1, 8, 2044, 18475776, ... |
Closed forms are summarized in the following table, where is a Lucas number, is a Stirling number of the second kind, and is a gamma function.
graph | chromatic invariant formula |
antiprism graph | |
complete bipartite graph | |
complete graph | {1 for n=1; (n-2)! otherwise" src="https://mathworld.wolfram.com/images/equations/ChromaticInvariant/Inline48.svg" style="height:68px; width:208px" /> |
complete tripartite graph | |
-crossed prism graph | |
cycle graph , | 1 |
empty graph | {1 for n=1; (-1)^nn otherwise" src="https://mathworld.wolfram.com/images/equations/ChromaticInvariant/Inline55.svg" style="height:68px; width:199px" /> |
gear graph | |
helm graph | 0 |
ladder graph | 1 |
ladder rung graph | {1 for n=1; 0 otherwise" src="https://mathworld.wolfram.com/images/equations/ChromaticInvariant/Inline59.svg" style="height:68px; width:130px" /> |
Möbius ladder | |
pan graph | 0 |
path graph | {0 for n=1, 2; 1 otherwise" src="https://mathworld.wolfram.com/images/equations/ChromaticInvariant/Inline63.svg" style="height:68px; width:149px" /> |
prism graph | |
star graph | {1 for n=1, 2; 0 otherwise" src="https://mathworld.wolfram.com/images/equations/ChromaticInvariant/Inline67.svg" style="height:68px; width:149px" /> |
sun graph | |
sunlet graph | 0 |
web graph | 0 |
wheel graph |
Biggs, N. L. Algebraic Graph Theory, 2nd ed. Cambridge, England: Cambridge University Press, pp. 107-109, 1993.
Devillers, J. and Balaban, A. T. (Eds.). Topological Indices and Related Descriptors in QSAR and QSPR. Amsterdam, Netherlands: Gordon and Breach, 1999.
Sloane, N. J. A. Sequences A000027/M0472, A000142/M1675, A000295/M3416, A000325, and A048144 in "The On-Line Encyclopedia of Integer Sequences."