The continuum limit and integer-valued vacuum charge

We consider a topologically trivial field theory defined in a large box of size L and exploit the enumeration of states to point out that the vacuum charge is integral, contrary to what a commonly used formula seems to suggest. We show that the large L limit is subtle: Standard anticommutation relations require the presence of a somewhat unfamiliar normalization factor which in turn leads to observable effects for the vacuum charge density. (C) 1998 American Institute of Physics. [S0021-3640(98)00117-0].