Physicists simulate colliding wormholes, find 28% horizon shrinkage and unique gravitational‑wave bursts

What the simulations showed

Physicists Nikita M. Shirokov (Moscow Institute of Physics and Technology) and Ilya Nachevsky (Higher School of Economics) built a three‑dimensional numerical model of two Ellis‑Bronnikov wormholes – a traversable solution that relies on a so‑called phantom scalar field with negative‑energy properties. By varying the initial separation, trajectories and scalar‑field parameters they observed a range of outcomes.

• Attraction or repulsion – In many runs the wormholes either pulled toward each other or pushed apart, with their throats expanding dramatically during a close fly‑by.
• Common apparent horizon – When the throats moved directly toward one another, a shared apparent horizon formed around both, essentially a nascent black‑hole region encompassing the two wormholes.
• Horizon shrinkage – As the phantom field fell into the collapsing zone, the apparent horizon lost about 28 % of its area. This behaviour contradicts Stephen Hawking’s 1971 black‑hole area theorem, which assumes ordinary (positive) energy conditions. The theorem does not apply to apparent horizons or exotic negative‑energy fields, so the result is not a violation but a striking illustration of how such matter can alter horizon dynamics.

Gravitational‑wave signatures

Both black‑hole and wormhole mergers generate ripples in space‑time, but the simulated wormhole encounters produced a markedly different waveform. Instead of the familiar “chirp” – a steadily rising frequency and amplitude – the wormhole collisions emitted short, sharp bursts. The exact shape and strength depended on whether the wormholes collided head‑on or merely grazed each other. Even some fly‑by events, without a common horizon, generated strong bursts.

The authors note that a similar‑looking burst was observed in the LIGO detection GW190521 (2019). While the study does not claim a direct link, it underscores the need to consider exotic scenarios when interpreting atypical signals.

Detectability prospects

Wormholes that formed in the early universe would have their gravitational‑wave frequencies stretched by cosmic expansion, pushing them below the sensitivity bands of current detectors such as LIGO and the upcoming space‑based LISA mission. For the bursts described in the simulations to be observable, the wormholes would need to arise much later in cosmic history – a process that remains speculative.

Why the work matters

Even though wormholes are still hypothetical, the study provides a concrete set of predictions that can guide future data analysis. If a short‑duration burst is recorded that does not fit the black‑hole chirp template, researchers now have a theoretical model to test against. Moreover, the horizon‑shrinkage result offers a rare glimpse into how exotic matter could bend the rules of general relativity.

The paper is currently a preprint on arXiv (2026) and has not yet undergone peer review. The next step will be to compare the predicted waveforms with forthcoming observations from upgraded ground‑based interferometers and space‑based missions.

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Key take‑aways

• Ellis‑Bronnikov wormholes can interact in ways that produce a common apparent horizon.
• The apparent horizon can shrink by roughly 28 %, a behaviour enabled by the phantom scalar field.
• Gravitational‑wave bursts from these collisions are brief and lack the chirp pattern of black‑hole mergers.
• Detectability hinges on late‑time wormhole formation, a scenario that remains uncertain.

The findings expand the catalogue of potential gravitational‑wave sources and highlight the importance of modelling exotic space‑time objects alongside conventional astrophysical events.