Tohoku Mathematical Journal
2000

December
SECOND SERIES VOL. 52, NO. 4

Tohoku Math. J.
52 (2000), 555-577

Title CONFIGURATIONS OF CONICS WITH MANY TACNODES

Author Gábor Megyesi

(Received April 14, 1999)
Abstract. We investigate configurations of conics in the projective plane which have the property that the number of tacnodes is equal or close to the upper bound obtained from the Miyaoka-Yau inequality. We show that for 5 conics there are exactly 3 configurations, including 2 new ones, achieving the maximum 17 tacnodes, and for 6 conics the maximum number of tacnodes is 22, which together with previous results implies that the Miyaoka-Yau bound can never be achieved.

2000 Mathematics Subject Classification. Primary 14N05.

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