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No realistic wormholes from ghost-free scalar-tensor phantom dark energy

Kirill A. Bronnikov·Alexei A. Starobinsky
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Abstract

It is proved that no wormholes can be formed in viable scalar-tensor models of dark energy admitting its phantom-like ($w < -1$) behaviour in cosmology, even in the presence of electric or magnetic fields, if the non-minimal coupling function $f(Φ)$ is everywhere positive and the scalar field $Φ$ itself is not a ghost. Some special static, spherically symmetric wormhole solutions may exist if $f(Φ)$ is allowed to reach zero or to become negative, so that the effective gravitational constant becomes negative in some region making the graviton a ghost. If $f$ remains non-negative, such solutions require severe fine tuning and a very peculiar kind of model. If $f < 0$ is allowed, it is argued (and confirmed by previous investigations) that such solutions are generically unstable under non-static perturbations, the instability appearing right near transition surfaces to negative $f$.

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Kirill A. Bronnikov, Alexei A. Starobinsky. 2006-12-05. No realistic wormholes from ghost-free scalar-tensor phantom dark energy. https://doi.org/10.1134/s0021364007010018

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