Dunce hat

Description

The Dunce hat. Made of 8 vertices and 17 facets. The vertices with the same lable should be identified.

This is a famous example of non-collapsible but contractible example.

Properties.

Not constructible but Cohen-Macaulay.

Datum

dunce_hat.dat

Some table

vertex decomposable?	no
extendably shellable?	no
shellable?	no
constructible?	no
Cohen-Macaulay?	yes
partitionable?	yes
topology	Dunce hat
f-vector	(1,8,24,17)
h-vector	(1,5,11,0)
made by	Whitehead(?)

References

E.C.Zeeman, On the dunce hat, Topology 2 (1964), 341-358.