Gravitational Phantoms: Domain Walls Instead of Black Holes ✦
We compared two hypotheses for short gravitational-wave signals GW190521 and GW231123: the merger of very massive black holes (BH) and the response of 'domain walls' — hypothetical folds of dark matter. In each case, the BH version was more convincing, but the margin was smaller than usual. For the first time, a joint analysis was performed: it turned out that both signals are compatible with a single dark-matter field, and the wall parameters matched even when processed independently. Interestingly, when simulated wall signals were injected into noise, detectors often attributed them to black holes with large spin — an important hint for future searches.
On May 14, 2019, LIGO detectors registered a gravitational burst that didn't fit the usual mold. Event GW190521 appeared as a collision of two black holes weighing 85 and 66 solar masses. The resulting hole of 142 solar masses landed right in the "forbidden" range — where stellar collapses leave almost no trace. Two years later came GW231123 — a short signal with suspiciously large components and unexpected spins. Astrophysicists grew concerned: either we misunderstand stellar evolution, or nature has thrown a curveball.
That curveball might turn out to be dark matter — but not in the familiar form of particles, rather as ancient cracks in the very fabric of reality. As the infant Universe cooled after the Big Bang, its fundamental fields fractured into domains with different vacuum states, like a pane of shattered glass. The boundaries between them — domain walls — are frozen as giant rifts, quantum scars that thread through the cosmos. They carry colossal energy, but interact with matter almost ghostly: shifting nature's constants for a split second. The idea traces back to the insights of Vera Rubin: half a century ago, she proved the Universe is full of the invisible, and now we may be grasping not a particle, but space itself.
So what does a wall "sound" like in a detector? Passing through the four-kilometer arms of an interferometer, the domain's scalar field shifts the phase and polarization of light — producing a short pulse, morphologically similar to a burst from a merging, precessing pair of black holes. The authors of the new work, building on ideas from Rainer Weiss and colleagues, built an eight-parameter model of this response and compared it with the classic scenario. At first glance, the Bayesian verdict is unambiguous: a Bayes factor logarithm of 12.2 for GW231123 and 11.3 for GW190521 — in favor of black holes. But the catch is that "honest" signals from modeled mergers typically yield values of 23 and 41. The suspiciously low contrast means the data aren't particularly discriminating — a domain wall and a pair of black holes are almost indistinguishable.
The joint analysis added intrigue. Both events, separated by three years, fit beautifully into a single set of parameters for the dark sector: a scalar field mass of ~10⁻¹² eV, a wall speed of ~0.026 the speed of light, and an integer ratio N_ratio = 3. Such a coincidence isn't yet proof, but it provides a decisive test: if future bursts follow the same pattern, black holes will gain some serious competition.
Thus a new observational paradigm is born. The Earth becomes a giant dark matter detector, and the routine of gravitational-wave observatories fills with philosophical meaning. We are learning to read the elusive script of the early Universe: phase transitions, broken symmetries, the birth of mass. A dozen such events, woven into a coherent picture, would let us declare: dark matter is not a scattering of particles, but a field configuration frozen in the first moment of existence. And then the three-body problem will gain a fourth dimension — not a star or a planet, but silent geometry, which right now may be shifting the hands of atomic clocks in your room by an imperceptible fraction of a second.
🎯 If the hypothesis is correct, then every day a domain wall a hundred meters thick passes through the Earth — and it can only be noticed by a fleeting phase shift of a laser beam in a kilometers-long interferometer.
🎬 The idea of macroscopic quantum objects passing silently through the Earth echoes the "Dark Forest" hypothesis — about hidden cosmic structures subtly influencing reality. It seems to have stepped right out of science fiction, where invisible "strings" or multidimensional defects pierce the cosmos, reminding us: the Universe may turn out to be far more bizarre than we're used to thinking.