A Chern-simons E8 Gauge Theory of Gravity in D = 15, Grand Unification and Generalized Gravity in Clifford Spaces

A novel Chern-Simons E8 gauge theory of Gravity in D = 15 based on an octic E8 invariant expression in D = 16 (recently constructed by Cederwall and Palmkvist) is developed. A grand unification model of gravity with the other forces is very plausible within the framework of a supersymmetric extension (to incorporate spacetime fermions) of this Chern-Simons E8 gauge theory. We review the construction showing why the ordinary 11D Chern-Simons Gravity theory (based on the Anti de Sitter group) can be embedded into a Clifford-algebra valued gauge theory and that an E8 Yang-Mills field theory is a small sector of a Clifford (16) algebra gauge theory. An E8 gauge bundle formulation was instrumental in the understanding the topological part of the 11-dim M -theory partition function. The nature of this 11-dim E8 gauge theory remains unknown. We hope that the Chern-Simons E8 gauge theory of Gravity in D = 15 advanced in this work may shed some light into solving this problem after a dimensional reduction.