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arXiv · hep-th/0303116

Strong Interactions and Stability in the DGP Model

Markus A. Luty·Massimo Porrati·Riccardo Rattazzi
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Abstract

The model of Dvali, Gabadadze, and Porrati (DGP) gives a simple geometrical setup in which gravity becomes 5-dimensional at distances larger than a length scale λ_{DGP}. We show that this theory has strong interactions at a length scale λ_3 ~ (λ_{DGP}^2 / M_P)^{1/3}. If λ_{DGP} is of order the Hubble length, then the theory loses predictivity at distances shorter than λ_3 ~ 1000 km. The strong interaction can be viewed as arising from a longitudinal `eaten Goldstone' mode that gets a small kinetic term only from mixing with transverse graviton polarizations, analogous to the case of massive gravity. We also present a negative-energy classical solution, which can be avoided by cutting off the theory at the same scale scale λ_3. Finally, we examine the dynamics of the longitudinal Goldstone mode when the background geometry is curved.

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Markus A. Luty, Massimo Porrati, Riccardo Rattazzi. 2003-03-12. Strong Interactions and Stability in the DGP Model. https://doi.org/10.1088/1126-6708%2F2003%2F09%2F029

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