Blanusa's Snark

Written by prof.dr Ivan Ivansic
University of Zagreb
© On this web with kind permission of the author

The Croatian Mathematical Society has proposed to The Croatian Post to notify The World Mathematical Year 2000 (WMY 2000) by a special stamp issue. The Croatian Post has accepted this proposal and issued the stamp on the figure. The stamp was presented on June 15, 2000; the first day of 2nd Croatian Matehamatical Congress.

The stamp depicts the Blanusa snark (D. Blanusa, Problem cetiriju boja, Glasnik Mat. Fiz. Astr. Ser. II. 1(1946), 31-42) discovered by late Professor Danilo Blanusa (13-1987) of The University of Zagreb, and published in the quoted paper. In that paper D. Blanusa treats the Four Colour Problem and proposes to investigate all connected and without bridges uncolorable trivalent graphs and try to characterize them and see if there exists any planar one or not. Beside this idea he has offered and depicted graph showning that the Petersen graph is not the only one of this type.

Soon, W.T. Tutte discovered the next one (Blanche Descartes, Network-colourings, The Mathematical Gazette (London) 32(1948), 67-69). In the private correspondence Professor Tutte wrote: "I saw Blanusa's paper soon after it appeared. Alas, I did not understand the language, but the diagram made all clear!". Step by step further discoveries led to the branch of Graph Theory called Theory of Snarks. Then name "snark" was proposed by Martin Gardner (Scientific American 234 No 4(1976), 126-130). The term "snark" owes its origins to the Snark of Lewis Carroll fame ("The hunting of the Snark"). The Croatian Mathematical Society has Blanusa's snark in its logo.

Croatian Science