Sylvain Petitjean

activity

20042007

most citedHadwiger and Helly-type theorems for disjoint unit spheres

5 citations · 8 across the 3 of their papers we have counts for

collaborators

3 papers

cs.CG2007★ 5 cited

Hadwiger and Helly-type theorems for disjoint unit spheres

Otfried Cheong, Xavier Goaoc, Andreas Holmsen +1

We prove Helly-type theorems for line transversals to disjoint unit balls in $R^{d}$ . In particular, we show that a family of $n \geq 2 d$ disjoint unit balls in $R^{d}$ has a line…

math.MG2006

Line transversals to disjoint balls

Ciprian Borcea, Xavier Goaoc, Sylvain Petitjean

We prove that the set of directions of lines intersecting three disjoint balls in $R^{3}$ in a given order is a strictly convex subset of $S^{2}$ . We then generalize this result to $n$ …

math.AG2004★ 3 cited

On tangents to quadric surfaces

Ciprian Borcea, Xavier Goaoc, Sylvain Lazard +1

We study the variety of common tangents for up to four quadric surfaces in projective three-space, with particular regard to configurations of four quadrics admitting a continuum o…