Fuzzball

Fuzzball is a concept in string theory and quantum gravity that proposes a reimagined description of black holes. The fuzzball hypothesis suggests that what is traditionally thought of as the black hole interior is instead a quantum bound state of strings and branes—an extended, highly quantum object called a fuzzball. In this view, there is no event horizon or singularity in the conventional sense; instead, each black hole microstate corresponds to a distinct, horizonless geometry with the same macroscopic quantities such as mass, charge, and angular momentum.

The core idea is that the exterior spacetime of a fuzzball agrees with general relativity at large distances, but the interior structure is replaced by a quantum configuration. Hawking radiation, rather than arising from quantum fields on a fixed background, is produced by interactions at the fuzzball surface. Because the fuzzball geometries encode microstate information, the framework aims to provide a mechanism for information to be carried away by radiation and to account for black hole entropy through microstate counting.

Status and reception: The fuzzball program has produced explicit microstate geometries in certain controlled settings, especially for supersymmetric or near-extremal black holes in higher-dimensional string theory. Critics argue that it remains unclear how to extend these constructions to generic astrophysical black holes and that a complete accounting of all microstates is lacking. Proponents contend that fuzzballs are compatible with holography and offer a path to resolving the information paradox, though the idea remains an area of active research rather than established consensus.

See also: black hole information paradox, microstate geometry, holography, black hole thermodynamics.