Unimodular triangulation and Ehrhart polynomials Let $P$ be a convex lattice polytope. Then it has a polynomial Ehrhart function.
I am interested in what can  be said about the Ehrhart polynomial when 
$P$ has any of the properties


*

*is integrally closed

*has a unimodular triangulation

*has a unimodular pulling triangulation

*is compressed


Specifically, does any of these properties imply that the coefficients of the Ehrhart polynomial are non-negative?
 A: I don't think you can generally conclude the nonnegativity of Ehrhart polynomials when expressed in the standard monomial basis; however, the more natural basis for Ehrhart polynomials is given by the binomial coefficients $\binom{n+d} d$, $\binom{n+d-1} d$, ..., $\binom n d$ (here $n$ is the variable of the polynomial and $d$ is the dimension of $P$). Stanley proved in 1980 that the coefficients of the Ehrhart polynomial of $P$ written in terms of this basis are nonnegative. This coefficient vector is known as the $h^*$-vector, $\delta$-vector, or Ehrhart $h$-vector of $P$. Here are some things that are known and connected to your question:
If $P$ has a unimodular triangulation $T$ then the $h^*$-vector of $P$ equals the $h$-vector of $T$ (a result contained in the aforementioned 1980 paper by Stanley). (I don't think a pulling triangulation buys anything extra, short of nice properties of the $h$-vector.)
For the case that $P$ is compressed, I believe the state of the art is described in a 2007 paper by Bruns and Roemer in JCTA.
For the case that $P$ is integrally closed, you may consult a recent preprint by Braun and Davis.
A: To add a partial answer, something I should have thought of before:
Every lattice polytope $P$ can be made into an integral polytope, by maginfying it with a sufficiently large factor. It is known that the dimension of $P$ suffices, to $dP$ is integrally closed. However, if $f(x)$ is the Ehrhart polynomial for $P$, then naturally $f(dx)$ is the Ehrhart polynomial for $dP$.
Notice that the sign of the coefficients in $f(x)$ and $f(dx)$ are the same.
Hence, just signs of coefficients are not more special for Ehrhart polynomials of integrally closed polytopes.
