Abstract:

We consider a diffeomorphism invariant theory of a gauge field valued in a Lie algebra that breaks spontaneously to the direct sum of the spacetime Lorentz algebra, a Yang-Mills algebra, and their complement. Beginning with a fully gauge invariant action – an extension of the Plebanski action for general relativity – we recover the action for gravity, Yang-Mills, and Higgs fields. The low-energy coupling constants, obtained after symmetry breaking, are all functions of the single parameter present in the initial action and the vacuum expectation value of the Higgs.

Here's the last paragraph of the conclusion:

Much remains to be done to investigate this theory. The gravitational sector needs to be better understood [16, 17]. Since the action and equations of motion are low-order polynomials, we believe that progress can be made on the quantization of the unified theory, but this remains to be investigated. In addition, one can consider more general versions of an extended Plebanski action in which Φ³, in (1), is replaced by a scalar function, U(Φ), as in [11]. While much remains to be done, it is now clear that the line of thought that began with the work of Plebanski and Ashtekar yields a natural and simple proposal for the unification of all known interactions.

What does everybody else think?