*Wissenschaftliches Programm* *Liste der Vortragenden*

**Sektion 12**

Freitag, 22.09.2000,
14.00–14.20 Uhr, WIL A 124

#### Günter M. Ziegler, TU Berlin

We introduce two parameters, the “fatness” and the “complexity” of a 4-dimensional polytope, both to be
computed in terms of the flag vector. It is not clear whether these parameters are at all bounded, but we
provide constructions and examples of polytopes that are “fatter” and “more complex” than the examples
known up to now.

Our examples disprove conjectured flag-vector inequalies by Bayer and by Billera and Ehrenborg, and
they include the first infinite family of 4-polytopes that are both 2-simple and 2-simplicial.