A textbook black hole resembles a perfectly smooth sphere: everything outside it calmly flies off to infinity. However, quantum gravity paints a different picture. Recently, within loop quantum gravity, a solution was found — a 'Kruskal' black hole where spacetime beyond the horizon behaves differently. Far from it, there is no familiar emptiness: an invisible energy seems to be spread out, preventing massive particles from escaping far. This is like a whirlpool in the ocean, where the water around it does not calm down but remains agitated at any distance.
Physicists applied to this hole a method for calculating quantum vacuum polarization — a way to measure how much the vacuum 'boils' under the influence of curvature. They numerically computed a quantity showing the activity of a scalar field outside. It turned out that the key parameter of quantum-like models (epsilon, which tracks the strength of corrections) enhances field fluctuations right at the horizon. A bit farther away, a weak negative tail appears — the field's response to the curved background, which is absent for an ordinary Schwarzschild hole.
The calculation served as a consistency check: quantum fluctuations faithfully follow local curvature without producing wild anomalies outside. This is a small but important step toward understanding how spacetime curvature and the quantum world coexist.
The epsilon parameter in this model is so tiny for real black holes that even the most precise instruments would not notice a difference from an ordinary black hole — the effect drowns in the natural noise of the cosmos.
In Stanislaw Lem's novel 'Solaris', the planet's ocean seems to sense the presence of humans — similarly, the quantum field 'feels' the curvature of a black hole, responding even to minuscule corrections.