A black hole usually hides its singularity behind an event horizon — an invisible boundary from which not even light can escape. But sometimes this 'cloak' is absent, and the singularity, a point where familiar physics breaks down, is exposed to an outside observer. Such objects are called naked singularities, and they cause theorists no end of trouble.
The authors of the new work took one of the most famous naked singularities — the Janis–Newman–Winicour (JNW) solution, generated by an ordinary scalar field (the simplest kind of matter, describable by a single number at each point). They applied a clever trick to its parameters: they rotated them into the complex plane using a so-called Wick rotation. The result was surprising: the singularity disappeared, and in its place emerged a traversable wormhole — a tunnel connecting two regions of flat spacetime. This is the famous Ellis class III wormhole, which was previously thought to be a completely different entity requiring exotic matter.
The discovery is far from accidental. The authors showed that the JNW solution belongs to a whole hierarchy of actions describing different theories of gravity. This means that 'fixing' one singularity automatically yields regular versions for an entire family of theories. So a single mathematical step untangles a knot of problems across different models.
as written by the authors arXiv:2607.10603
We propose a novel way to achieve the regularization of the JNW globally naked singularity sourced by the canonical Einstein minimally coupled scalar field (EMS). The key idea is to complexify (Wick rotate) the JNW parameters, which yields a regular metric that surprisingly represents a twice asymptotically flat regular traversable wormhole, famously known as the Ellis class III wormhole sourced by the ghost EMS. We begin by arguing that the JNW solution belongs to a hierarchy of actions describing different gravity theories, which indicates that a regularized version of JNW automatically adds corresponding regular versions to the hierarchy of gravity theories.
The Ellis class III wormhole is one of the few examples of traversable wormholes without singularities that does not require exotic matter with negative energy. Instead, it uses a so-called 'ghost' scalar field.
The idea of wormholes as portals between distant points in space is the basis of the plot of the movie 'Interstellar', where heroes travel through such a tunnel to find a new home for humanity.