Dear All,

Today at 15:00, there will be a Geometry seminar, for technical reasons postponed to exam period. Anybody can attend.

The announcement is below.

Best regards, Pavel

----------------------------------- Geometry Seminar today (Tue Jan 17) at 15:00 in S9

Speaker: Jan Soukup

Improving the lower bound on opaque sets for equilateral triangle by Taisuke Izumi

An opaque set (or a barrier) for U in the plane is a set B of finite-length curves such that any line intersecting U also intersects B. We consider the lower bound on the shortest barrier when U is the unit-size equilateral triangle. In the paper they improved a general lower bound of 3/2 to 3/2+5*10^(-13). We will also look at the case of a square instead of triangle from a different paper where they also improved the best known lower bound. https://www.sciencedirect.com/science/article/pii/S0166218X16302232 ----------------------------------