***** KAIST Discete Math Semianr *****

DATE: March 6th, Thursday

TIME: 3PM-4PM

PLACE: E6-1, ROOM 1409

SPEAKER: Otfried Cheong, KAIST, Korea.

TITLE: Helly-Type Theorems for Line-Transversals to Spheres


We prove Helly-type theorems for line transversals to disjoint unit
spheres in R^d. In particular, we show that a family of n >= 2d disjoint
unit spheres in R^d has a line transversal if, for some ordering of the
balls, any subfamily of 2d balls admits a line transversal consistent
with this ordering.   We also discuss generalizations that drop the
ordering requirement and to spheres with arbitrary radius.


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