Neutron stars are the compressed remnants of massive stars: their matter is squeezed so tightly that a thimble-sized amount would weigh a colossal amount. If dark matter, the mysterious invisible substance thought to hold galaxies together with its gravity, accumulates inside such an object, under certain conditions this accumulation becomes fatal. In ordinary three-dimensional space, triggering a catastrophic scenario would require an unimaginable mass, but the hypothesis of hidden, curled-up dimensions radically changes the game.

It helps to think of gravity as curved spacetime, like a taut trampoline sheet: massive bodies create dents in it, causing other objects to roll along these depressions. Particles of dark matter, like tiny pellets, individually only slightly press into the sheet. However, extra dimensions, if they exist, act like a magnifying glass for gravity: they "roll" these pellets into a single lead ball whose weight tears the sheet, giving rise to a black hole. Thus, the ideas of Fritz Zwicky, who in the 1930s predicted the existence of neutron stars, and Vera Rubin, who convincingly proved the reality of dark matter through galaxy rotation speeds in the 1970s, converge in this grim scenario.

The scenario takes an unexpected turn: the resulting miniature black hole does not evaporate instantly, as the famous Hawking radiation would require. Extra dimensions slow this process, allowing the hole to devour the neutron star entirely. This outcome imposes strict constraints on the properties of dark matter: if extra dimensions are real, then dark matter particles with masses heavier than a few tens of teraelectronvolts (TeV) are simply ruled out — otherwise we would observe too many destroyed neutron stars. For comparison, in flat three-dimensional space without hidden dimensions, the analogous mass threshold would be millions of orders of magnitude higher.