General second-order scalar-tensor theory and self-tuningTools Charmousis, Christos, Copeland, Edmund J., Padilla, Antonio and Saffin, Paul M. (2012) General second-order scalar-tensor theory and self-tuning. Physical Review Letters, 108 (5). 051101/1-051101/. ISSN 1079-7114 Full text not available from this repository.AbstractStarting from the most general scalar-tensor theory with second order field equations in four dimensions, we establish the unique action that will allow for the existence of a consistent self-tuning mechanism on FLRW backgrounds, and show how it can be understood as a combination of just four base Lagrangians with an intriguing geometric structure dependent on the Ricci scalar, the Einstein tensor, the double dual of the Riemann tensor and the Gauss-Bonnet combination. Spacetime curvature can be screened from the net cosmological constant at any given moment because we allow the scalar field to break Poincar\'e invariance on the self-tuning vacua, thereby evading the Weinberg no-go theorem. We show how the four arbitrary functions of the scalar field combine in an elegant way opening up the possibility of obtaining non-trivial cosmological solutions.
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