  The problem of an enormously large energy density of the quantum vacuum is
discussed in connection with the concept of renormalization of physical
parameters in quantum field theory. Using the method of dimensional
regularization, it is recalled that the normal ordering procedure of creation
and annihilation operators is equivalent to a renormalization of the
cosmological constant leading to its zero and nonzero values in Minkowski
space-time and in the standard cosmological model, respectively. It is argued
that a frequently discussed gravitational effect, resulting from an enormously
large energy density described by the nonrenormalized (bare) cosmological
constant, might be nonobservable much like some other bare quantities
introduced in the formalism of quantum field theory.
