Particle Creation in Global de Sitter Space: Bulk Space Consideration
  Recently in \cite{Anderson:2013zia, Anderson:2013ila}, it was shown that global de Sitter space is unstable even to the massive particle creation with no self-interactions. In this paper we study the instability by making use of the coordinate-independent plane wave in de Sitter space, within this formalism, we show that the previous results of instability of de Sitter space due to the particle creation can be generalized to higher-spin fields in a straightforward way. The so-called plane wave are defined globally in de Sitter space and de Sitter invariance is manifest since such modes are deduced from the group theoretical point of view by the means of the Casimir operators. In fact, we employ the underling symmetry of embedding space namely the $4+1$ dimensional flat space to write the field equations and the solutions can be obtained in terms of the plane wave in embedding space. 
M. Reza Tanhayi
gr-qc