Null energy condition and causality in Lifshitz holography
- Department of Physics, University of Washington Seattle, Seattle, Washington 98195-1560 (United States)
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455 (United States)
We use a WKB approximation to establish a relation between the wave front velocity in a strongly coupled theory and the local speed of light in a holographic dual, with our main focus put on systems with Lifshitz scaling with dynamical exponent z. We then use Einstein equations to relate the behavior of the local speed of light in the bulk with the null energy condition (NEC) for bulk matter, and we show that it is violated for Lifshitz backgrounds with z<1. We study signal propagation in the gravity dual and show that violations of the NEC are incompatible with causality in the strongly coupled theory, ruling out as holographic models Lifshitz backgrounds with z<1. We argue that causality violations in z<1 theories will show up in correlators as superluminal modes and confirm this for a particular example with z=1/2. Finally, as an application, we use z<1 solutions to uncover regions of the parameter space of curvature squared corrections to gravity where the NEC can be violated.
- OSTI ID:
- 21432373
- Journal Information:
- Physical Review. D, Particles Fields, Vol. 82, Issue 8; Other Information: DOI: 10.1103/PhysRevD.82.084002; (c) 2010 American Institute of Physics; ISSN 0556-2821
- Country of Publication:
- United States
- Language:
- English
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