科研之友
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摘要
The basic building block for Lorentz-invariant and ghost-free massive gravity is the square root of the combination g(-1)eta, where g(-1) is the inverse of the physical metric and eta is a reference metric. Since the square root of a matrix is not uniquely defined, it is possible to have physically inequivalent potentials corresponding to different branches. We show that around the Minkowski background, the only perturbatively well-defined branch is the potential proposed by de Rham, Gabadadze and Tolley. On the other hand, if Lorentz symmetry is broken spontaneously, other potentials exist with a standard perturbative expansion. We show this explicitly building new Lorentz-invariant, ghost-free massive gravity potentials for theories that in the background preserve rotational invariance but break Lorentz boosts.
- 出版日期2015-6-29
