Given an o-minimal expansion ℳ of a real closed field R which is not polynomially bounded. Let ${}^{\infty }$ denote the definable indefinitely Peano differentiable functions. If we further assume that ℳ admits ${}^{\infty }$ cell decomposition, each definable closed subset A of Rⁿ is the zero-set of a ${}^{\infty }$ function f:Rⁿ → R. This implies ${}^{\infty }$ approximation of definable continuous functions and gluing of ${}^{\infty }$ functions defined on closed definable sets.

We propose a refinement of the notion of blow-Nash equivalence between Nash function germs, which has been introduced in [2] as an analog in the Nash setting of the blow-analytic equivalence defined by T.-C. Kuo [13]. The new definition is more natural and geometric. Moreover, this equivalence relation still does not admit moduli for a Nash family of isolated singularities. But though the zeta functions constructed in [2] are no longer invariants for this new relation, thanks to a Denef & Loeser...