  We present an extension of quantum field theory to the case when the
spacetime topology fluctuates (spacetime foam). In this extension the number of
bosonic fields becomes a variable and the ground state is characterized by a
finite particle number density. It is shown that when the number of fields
remains a constant, the standard field theory is restored. However, in the
complete theory the ground state has a nontrivial properties. In particular, it
produces an increase in the level of quantum fluctuations in the field
potentials and an additional renormalization of masses of particles. We examine
fluctuations of massless fields and show that in the presence of a temperature
(thermal state) these fluctuations has 1/f spectrum. Thus, the main prediction
of the theory is that our universe should be filled with a random
electromagnetic field which should produce an additional 1/f - noise in
electric circuits.
