%0 Journal Article
%T A characterization of simplicial polytopes with g_2=1
%A Eran Nevo
%A Eyal Novinsky
%J Mathematics
%D 2008
%I arXiv
%X Kalai proved that the simplicial polytopes with g_2=0 are the stacked polytopes. We characterize the g_2=1 case. Specifically, we prove that every simplicial d-polytope (d>=4) which is prime and with g_2=1 is combinatorially equivalent either to a free sum of two simplices whose dimensions add up to d (each of dimension at least 2), or to a free sum of a polygon with a (d-2)-simplex. Thus, every simplicial d-polytope (d>=4) with g_2=1 is combinatorially equivalent to a polytope obtained by stacking over a polytope as above. Moreover, the above characterization holds for any homology (d-1)-sphere (d>=4) with g_2=1, and our proof takes advantage of working with this larger class of complexes.
%U http://arxiv.org/abs/0804.1813v2