We view the number of
particles operator N as the infinitesimal generator of the Ornstein-Uhlenbeck
semigroup in an abstract Wiener setting. It is shown that if two functions f,
g in the domain of N agree a.e. on an open set 𝒪, then Nf = Ng on 𝒪.
The restriction of N to a large core acts as an infinite dimensional partial
differential operator L, and it is shown that L may be defined locally in an Lloc2
setting.