Flip-connectivity of triangulations of the product of a tetrahedron and   simplex
  A flip is a minimal move between two triangulations of a polytope. An open question is whether any two triangulations of the product of two simplices can be connected through a series of flips. This was proven in the case where one of the simplices is a triangle by Santos in 2005. In this paper we extend this to when one of the simplices is a tetrahedron. 
Gaku Liu
math.CO