ARS MATHEMATICA CONTEMPORANEA
Wilfried Imrich's 75th Birthday Colloquium
Wilfried Imrich was born on May 25th, 1941 in Vienna. On June 17th, 2016, a colloquium was organized at the Graz University of Technology to celebrate his 75th birthday. The colloquium started with a laudatio by Peter Kirschenhofer (Leoben). In the central part of the event the following talks were presented:
(i)	Ultrametric spaces, trees, and random walks (Wolfgang Woess, Graz),
(ii)	Automorphism groups of one-ended graphs (Florian Lehner, Hamburg),
(iii)	Extending Wiener index to arbitrary partitions (Sandi Klavar, Ljubljana), and
(iv)	From chaos on trees to symmetry breaking (Rafa Kalinowski, Krakw).
We do not intend to summarize Wilfried's outstanding career here (see [1]), but will just mention that he is the world's leading expert on graph products and that, because of his co-authorships with Lszl Babai, Lszl Lovsz, and Jaroslav Neetil, Wilfried has Erds number 2 in at least three ways. We do wish, however, to emphasize his deep connections with the Slovene graph theory school and his lasting impact on it. Wilfried was an important figure in the development of graph theory in Slovenia from its very beginning. Together with Tomo Pisanski he was a co-founder of the Ljubljana-Leoben graph theory seminar and had 3 Ph.D. students from Slovenia. He has also published several dozen joint papers with more than a dozen Slovenian co-authors, as well as three books on graph products that have become classic references for the field.
It is a pleasure to conclude this short report on Wilfried Imrich's 75th Birthday Colloquium by pointing to Wilfried's impressive mathematical achievements obtained in the last years. Hence, we are looking forward to future beautiful theorems from him!
Sandi Klavar Associate Editor
References
[1] P. Kirschenhofer, Laudatio for Professor Dr. Wilfried Imrich on the occasion of his 75th birthday,
http://amc-journal.eu/index.php/amc/article/view/1253/1023.
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