University of Cambridge > > DAMTP Friday GR Seminar > Graviton time-delay in Lovelock gravity

Graviton time-delay in Lovelock gravity

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Lovelock theories provide a natural generalisation to GR in higher dimensions. Interestingly, in these theories gravitons can propagate faster or slower than light. It was recently observed (Camanho et al. 2014) that, in a Lovelock theory, gravitons can experience a negative Shapiro time delay when crossing a gravitational ‘shock-wave’. Using this effect it was then argued that closed causal curves may form, making the theory unviable. Instead of the singular shock-wave geometries, we will consider gravitons propagating on smooth black hole spacetimes and show that a negative time delay is possible in this setting. We will then discuss issues related to the construction of closed causal curves and why the existence of causally pathological solutions wouldn’t be sufficient to discard the theory.

This talk is part of the DAMTP Friday GR Seminar series.

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