2009/05/11 by Patrick Das Gupta, Gupta, Patrick Das
Mathematics · Physics and Astronomy · #FOS: Physical sciences #General Relativity and Quantum Cosmology (gr-qc) #Mathematical Physics (math-ph) #gr-qc #math-ph #math.MP
paper · pdf · doi:10.48550/arxiv.0905.1621
Electromagnetic as well as gravitational Chern-Simons like terms associated with the four-form included, four references added
arxiv created 2011/12/02 · arxiv updated 2011/12/05
We consider the dynamics of a four-form field w , treating it as a distinct physical degree of freedom, independent of the metric. The equations of motion are derived from an action which, besides having the standard Hilbert-Einstein term and the matter part, consists of a new action for w . The evolution of w in a flat FRW universe is studied, and it is shown that the parameters of the theory admit solutions wherein it is possible to have an equation of state pϕ≈ -εϕ, so that it leads to an accelerating universe. We also put forward electromagnetic as well as gravitational `Chern-Simons' like terms that arise naturally in 4D, entailing a modified Einstein-Maxwell equation and an enlarged system of Einstein equation involving a Cotton tensor. We demonstrate that the scalar-density associated with w can be employed to construct a generalized exterior derivative that converts a p-form density to a (p+1)-form density of identical weight.