Scalar multi-wormholes

In 1921 Bach and Weyl derived the method of superposition to construct new axially symmetric vacuum solutions of General Relativity. In this paper we extend the Bach-Weyl approach to non-vacuum configurations with massless scalar fields. Considering a phantom scalar field with the negative kinetic energy, we construct a multi-wormhole solution describing an axially symmetric superposition of $N$ wormholes. The solution found is static, everywhere regular and has no event horizons. These features drastically tell the multi-wormhole configuration from other axially symmetric vacuum solutions which inevitably contain gravitationally inert singular structures, such as `struts' and `membranes', that keep the two bodies apart making a stable configuration. However, the multi-wormholes are static without any singular struts. Instead, the stationarity of the multi-wormhole configuration is provided by the phantom scalar field with the negative kinetic energy. Anther unusual property is that the multi-wormhole spacetime has a complicated topological structure. Namely, in the spacetime there exist $2^N$ asymptotically flat regions connected by throats.Comment: 11 pages, 13 figure

Strong light-matter coupling: parametric interactions in a cavity and free-space

We consider parametric interactions of laser pulses in a coherent macroscopic ensemble of resonant atoms, which are possible in the strong coupling regime of light-matter interaction. The spectrum condensation (lasing at collective vacuum Rabi sidebands) was studied in an active cavity configuration. Parametric interactions under the strong light-matter coupling were proved even in free space. In contrast to bichromatic beats in a cavity, they were shown to appear due to interference between polaritonic wave packets of different group velocities.Comment: 4 pages, 2 figure