  We propose an effective harmonic oscillator model in order to treat the
fluctuations of the gravitational, strong and weak nuclear fields. With respect
to the gravitational field, first we use the model to estimate its fluctuating
strength, necessary to decohere the wavefunction of a cubic centimeter of air
at the standard temperature and pressure conditions. Second, the fluctuation of
a point mass through a distance equal to the Planck length leads to the
self-gravitational interaction of a particle, which can be related to its de
Broglie frequency. Third, by making the equality of the fluctuating field
strength with the gravitational field of a mass M at half of its Schwarzschild
radius, we obtain an estimate of the mass of the Universe. We also consider the
fluctuations of the strong nuclear field, as a means to estimate the separation
in energy between the ground state and the centroid of the excitated states of
the nucleon. Finally, taking into account the neutron-proton mass difference,
we use the fluctuations of the weak nuclear field in order to evaluate the weak
coupling constant.
