Supporting wormholes by spacetime parity and topology in Lovelock-Brans-Dicke gravity

Following the recent theory of Lovelock-Brans-Dicke gravity, we continue to investigate the conditions to support traversable wormholes by the gravitational effects of spacetime parity and topology, which arise from the nonminimal couplings of a background scalar field to the Chern-Pontryagin density and the Gauss-Bonnet invariant. The flaring-out condition indicates that a Morris-Thorne-type wormhole can be maintained by violating the generalized null energy condition, and thus also breaking down the generalized weak, strong, and dominant energy conditions; meanwhile, analyses of the zero-tidal-force solution show that the standard energy conditions in general relativity can still be respected by the physical matter threading the wormhole. In this situation, the two topological effects have to dominate over the ordinary-matter source of gravity, and the scalar field is preferred to be noncanonical. Also, we find that it is easier in Lovelock-Brans-Dicke than Brans-Dicke gravity to support wormholes while have the standard energy conditions protected.