  Recent observational data have shown two important results about cosmic
inflation: First, the primordial power spectrum is approximately scale
invariant. Secondly, the space-time geometry during inflation is quasi-de
Sitter. In this paper, we study the background field method and the concept of
negative norm states in the framework of Krein space to use in early universe
cosmology. For the inflaton field equation, based on the observations and
taking into account our studies, we suggest an alternative proposal. We will
take the quasi-de Sitter solutions as the physical geometry with the positive
norm and the pure de Sitter solutions as the background geometry with the
negative norm. In the following, we review the consequences of applying the
proposal to calculate some cosmological quantities.
