Enclosing a Compact Set in an O-minimal Expansion of $(\mathbb{R},+,\cdot,0,1 <)$

Abstract

Fix an o-minimal expansion $\mathcal{R}=(\mathbb{R},+,\cdot,0,1 <,...)$ of the real ordered field. Given $C^1$ functions $f_1,...,f_k$, $g_1,...,g_k:M\to\mathbb{R}$ on a definable cell $M$, let $h_{i,0}$ denote $f_i$ and $h_{i,1}$ denote $g_i$. Suppose that for all $\tau\in 2^{[k]}$, $H_{\tau}=(h_{1,\tau(1)},..,h_{k,\tau(k)}) :M\to \mathbb{R}^k$ is regular and proper on $M$, and that for all $i\in[k]$, $\{f_i=0\}$ and $ \{g_i=0\}$ are connected, and $\{f_i=0\}\cap \{g_i=0\}=\emptyset$. We show that then there exists a sequence $(\square_{i,\epsilon}:i\in[k],\epsilon \in \{0,1\})\in\{\leq ,\geq \}^{[k]\times\{0,1\}}$ such that the enclosed region $\underset{i\in[k]}{\bigcap}\{ f_i\square_{i,0} 0\}\cap \{ g_i\square_{i,1} 0\} $ is compact.