  The quantum field theory prediction of the cosmological constant is 120
orders of magnitude higher than the observed value. This is known as the
cosmological constant problem. Here, we deal with the cosmological constant as
a scalar field generated by the reduced extra dimensions, following
Kaluza-Klein reduction, in the superstring theory frame, where the vacuum
energy is the minimum of this field. We find methods for calculating the
cosmological constant, whose value is much lower than those obtained with the
current methods of quantum field theory. We conclude that the small
cosmological constant value could be explained by the behavior of the mentioned
scalar field, and finally we discuss a possible explanation for the observed
accelerated expansion of the Universe.
