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Conjecture For every
, there exists an integer
such that if
is a digraph whose arcs are colored with
colors, then
has a
set which is the union of
stables sets so that every vertex has a monochromatic path to some vertex in
.
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In the particular case of tournaments (and more generally when the stabilty number of is bounded), it has been proved by Bousquet, Lochet, and Thomassé [BLT].
Bibliography
[BLT] Nicolas Bousquet, William Lochet, Stéphan Thomassé: A proof of the Erdős-Sands-Sauer-Woodrow conjecture,
[SSW] B. Sands, N. Sauer and R. Woodrow, On monochromatic paths in edge-coloured digraphs. Journal of Combinatorial Theory, Series B, 33, (1982), 271--275.
* indicates original appearance(s) of problem.