In the asymptotic-safety scenario for gravity, nonzero interactions are
present in the ultraviolet. This property should also percolate into the matter
sector. Symmetry- based arguments suggest that nonminimal derivative
interactions of scalars with curvature tensors should therefore be present in
the ultraviolet regime. We perform a nonminimal test of the viability of the
asymptotic-safety scenario by working in a truncation of the Renormalization
Group flow, where we discover the existence of an interacting fixed point for a
corresponding nonminimal coupling. The back-coupling of such nonminimal
interactions could in turn destroy the asymptotically safe fixed point in the
gravity sector. As a key finding, we observe nontrivial indications of
stability of the fixed-point properties under the impact of nonminimal
derivative interactions, further strengthening the case for asymptotic safety
in gravity-matter systems.Comment: 13 pages, 8 figures, 1 tabl
There are various ways of defining the Wick rotation in a gravitational context. There are good arguments to view it as an analytic continuation of the metric, instead of the coordinates. We focus on one very general definition and argue that it is incompatible with the requirement of preserving the field equations and the symmetries at global level: in some cases the Euclidean metric cannot be defined on the original Lorentzian manifold but only on a submanifold. This phenomenon is related to the existence of horizons, as illustrated in the cases of the de Sitter and Schwarzschild metrics. 1
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