I'll first give intuition, and then give a precise statement.
For $|z|<1$, we have $\sum_{i \geq 0} z^i = 1/(1-z)$. For $|z|>1$, we have $\sum_{i<0} (-1) z^i=1/(1-z)$. Thus, the two functions
$\phi(i) = \begin{cases} 1 \quad i \geq 0 \\ 0 \quad i<0 \end{cases}$ and $\psi(i) = \begin{cases} 0 \quad i \geq 0 \\ -1 \quad i<0 \end{cases}$
have the "same" Fourier transform. This question is about generalizations of this phenomenon to higher dimensions.
Let $\phi : \mathbb{Z}^n \to \mathbb{R}$ be a function such that (1) $\phi$ can be written as a rational combination of the characteristic functions of finitely many rational cones and (2) there is a linear function $\lambda$ so that $\phi$ vanishes on $\{ e : \lambda(e) \leq 0 \} \setminus \{ 0 \}$. We define $$h(\phi) = \sum \phi(e) z^e.$$ This sum converges somewhere, and gives a rational function of $z$.
Given $\phi$ as above, and given a generic linear functional $\zeta$, one can show that there is a unique function $\phi^{\zeta}$ such that (1) $\phi$ can be written as a rational combination of the characteristic functions of finitely many cones (2) $\phi$ vanishes on $\{ e : \zeta(e) \leq 0 \} \setminus \{ 0 \}$ and (3) $h(\phi^{\zeta}) = h(\phi)$.
For example, the above computation shows that $\phi^{(-1)} = \psi$. If $\phi$ is the characteristic function of a simplicial cone, this operation is easy to describe. In principle, this means we can always calculate $\phi^{\zeta}$ by writing $\phi$ as a linear combination of simplicial cones.
If $\phi$ is the characteristic function of a cone, what is known about $\phi^{\zeta}$? For example, is it true that (a) all the values of $\phi^{\zeta}$ have the same sign (NO, counter-example below), or that (b) $\phi^{\zeta}$ only takes the values $-1$, $0$ and $1$?
