## Theory of Combinatorial Algorithms

Prof. Emo Welzl and Prof. Bernd Gärtner

# Mittagsseminar (in cooperation with M. Ghaffari, A. Steger and B. Sudakov)

 Mittagsseminar Talk Information

Date and Time: Thursday, April 15, 2010, 12:15 pm

Duration: This information is not available in the database

Location: CAB G51

Speaker: Ido Ben-Eliezer (Tel Aviv University)

## On the size Ramsey number of directed path

We study the size Ramsey number of directed path of length n in oriented graphs, where no antiparallel edges are allowed. We give nearly tight bounds for every fixed number of colors, showing that for every q\geq 1 there are constant c,c_q such that \frac{c_q n^{2q}\log^{1/q} n}{\log^{(q+2)/q}\log n} \leq r_e(\overrightarrow{P_n},q+1) \leq c n^{2q}\log^{2}{n}. In particular this shows that the size Ramsey number in oriented graphs is asymptotically larger than the size Ramsey number in general directed graphs.

Joint work with Michael Krivelevich and Benny Sudakov.

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