Causal Structures in Gauss-Bonnet gravity

Abstract

We analyze causal structures in Gauss-Bonnet gravity. It is known that Gauss-Bonnet gravity potentially has superluminal propagation of gravitons due to its noncanonical kinetic terms. In a theory with superluminal modes, an analysis of causality based on null curves makes no sense, and thus, we need to analyze them in a different way. In this paper, using the method of the characteristics, we analyze the causal structure in Gauss-Bonnet gravity. We have the result that, on a Killing horizon, gravitons can propagate in the null direction tangent to the Killing horizon. Therefore, a Killing horizon can be a causal edge as in the case of general relativity, i.e. a Killing horizon is the "event horizon" in the sense of causality. We also analyze causal structures on nonstationary solutions with $(D-2)$-dimensional maximal symmetry, including spherically symmetric and flat spaces. If the geometrical null energy condition, $R_{AB}{N}^A{N}^B\ge 0$ for any null vector $N^A$, is satisfied, the radial velocity of gravitons must be less than or equal to that of light. However, if the geometrical null energy condition is violated, gravitons can propagate faster than light. Hence, on an evaporating black hole where the geometrical null energy condition is expected not to hold, classical gravitons can escape from the "black hole" defined with null curves. That is, the causal structures become nontrivial. It may be one of the possible solutions for the information loss paradox of evaporating black holes.

Version accepted by PRD (v2): 11pages, 1 figure

References in corpus (14)

• Causality, Analyticity and an IR Obstruction to UV Completion
• Viscosity Bound and Causality Violation
• Beyond eta/s = 1/4pi
• On Holographic Entanglement Entropy and Higher Curvature Gravity
• Generalized Misner-Sharp quasi-local mass in Einstein-Gauss-Bonnet gravity
• Static and symmetric wormholes respecting energy conditions in Einstein-Gauss-Bonnet gravity
• Exact solutions for the Einstein-Gauss-Bonnet theory in five dimensions: Black holes, wormholes and spacetime horns
• Mimicking Lambda with a spin-two ghost condensate
• Lovelock black holes with maximally symmetric horizons
• Dynamical black holes with symmetry in Einstein-Gauss-Bonnet gravity
• Simple compactifications and Black p-branes in Gauss-Bonnet and Lovelock Theories
• From configuration to dynamics -- Emergence of Lorentz signature in classical field theory
• Spherically symmetric analysis on open FLRW solution in non-linear massive gravity
• Brane Universes with Gauss-Bonnet-Induced-Gravity

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• Holographic phase transition and Quasinormal modes in Lovelock gravity
• Quasilinear reformulation of Lovelock gravity