The Extended Relativity Theory in Born-Clifford Phase spaces with a lower and upper length scales and Clifford group geometric unification

We construct the Extended Relativity Theory in Born-Clifford-Phase spaces with an upper R and lower length lambda scales (infrared/ultraviolet cutoff). The invariance symmetry leads naturally to the real Clifford algebra Cl( 2, 6, R) and complexified Clifford Cl-C(4) algebra related to Twistors. A unified theory of all Noncommutative branes in Clifford-spaces is developed based on the Moyal-Yang star product deformation quantization whose deformation parameter involves the lower/ upper scale ((h) over bar lambda/R). Previous work led us to show from first principles why the observed value of the vacuum energy density (cosmological constant) is given by a geometric mean relationship rho similar to L-Planck(-2) R-2 = L-P(-4) (L-Planck/R)(2) similar to 10(-122)M(Planck)(4), and can be obtained when the infrared scale R is set to be of the order of the present value of the Hubble radius. We proceed with an extensive review of Smith's 8D model based on the Clifford algebra Cl( 1, 7) that reproduces at low energies the physics of the Standard Model and Gravity, including the derivation of all the coupling constants, particle masses, mixing angles,.... with high precision. Geometric actions are presented like the Clifford-Space extension of Maxwell's Electrodynamics, and Brandt's action related to the 8D spacetime tangent-bundle involving coordinates and velocities (Finsler geometries). Finally we outline the reasons why a Clifford-Space Geometric Unification of all forces is a very reasonable avenue to consider and propose an Einstein-Hilbert type action in Clifford-Phase spaces ( associated with the 8D Phase space) as a Unified Field theory action candidate that should reproduce the physics of the Standard Model plus Gravity in the low energy limit.