Gravity

However, what we have not investigated is what really happens at the instant t = 0? this time is usually referred to as the point of time of the Big Bang. Some of the models of the universe's evolution have clearly no singularity, like the k = 1 de Sitter model. Other models have a singularity. In this paper, we will be dedicated to cosmological singularities. We will start out with Einstein's field equations, in order to determine what we need to introduce some technical concepts that lead to the investigation of the existence of the singularities.