C. J. L. Doran, A. N. Lasenby and S. F. Gull.
Gravity as a Gauge Theory in the Spacetime Algebra
In F. Brackx and R. Delanghe, editors, Clifford Algebras and their Applications in Mathematical Physics. Deinze 1993 (Kluwer Academic, Dordrecht, 1993), p. 375-385.

Abstract: We outline a theory of gravitational interactions utilising the spacetime algebra - the geometric algebra of spacetime. The theory arises by demanding invariance under active Poincaré transformations. Making this symmetry local results in a first-order theory with 40 degrees of freedom. The matter-free field equations are presented, and are solved for radially-symmetric static fields. We discuss the behaviour of point particles under the fields described by these solutions, and compare and contrast the results with those of general relativity.

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