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The Black Hole's Doppelgängers: Dark Matter or Hidden Worlds? ✛ ✦

Original: "DARK-HIDE: Dark matter versus hidden dimensions in black hole images"
· Mohsen Fathi
arXiv:2607.13992 · 2026-07-15 · CC BY 4.0 · 1 min
General Relativity High Energy
From a shadow's snapshot alone, one can't tell what distorts it — invisible matter or curled-up dimensions.

Shadow images of a black hole, captured by interferometry (combining waves from many antennas), reveal a distorted silhouette. It's like looking through uneven glass: spacetime curvature from dark matter and gravity due to curled-up dimensions bends light rays almost identically. Numerical simulations and brightness measurements confirm it: twin shadows.

There is five times more dark matter than ordinary matter, but it can only be detected through its gravitational pull.

Only at the very edge of the hole, where space is scrunched to the limit, is there a difference: curled-up dimensions squeeze light just a bit tighter. This microscopic distinction in light bending is what future telescopes sensitive to polarization hope to capture. Then we'll know what lurks behind the shadow — invisible mass or hidden worlds. The idea traces back to the calculations of Schwarzschild and Chandrasekhar, and the name was coined by Wheeler.

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In theories with extra dimensions, a black hole acquires a distinctive 'tidal charge' — it can be negative, as if gravity pushes instead of pulls. This is impossible in ordinary physics.

Science fiction writers see black holes as gateways to parallel worlds. In Stanisław Lem's novel 'The Astronauts', characters pass through a black hole into another universe.

\Delta_{\text{DM}}(r)=r^2 - 2M\left[1+\frac{\varepsilon}{M}\mu_{\text{DM}}(r)\right]r + a^2
The extra term with ε and the function μ_DM(r) describes how the dark matter distribution around the hole curves spacetime more strongly than the hole’s mass alone.
\Delta_{\text{ED}}(r)=r^2 - 2Mr + a^2 + q
The constant q, the tidal charge, reflects the influence of higher dimensions; unlike ordinary electric charge, it can be negative and alter the gravitational field in the most unexpected ways.
Scientists
Stephen HawkingJacob BekensteinJohn Archibald WheelerEdward WittenJuan MaldacenaFritz Zwicky
Concepts
black hole tidal deformability kerr black hole kerr metric horizon area no-hair theorem inner horizon Hawking area theorem barrow entropy iron k alpha reverberation EHT tidal charge schwarzschild metric spin parameter logarithmic correction holographic principle Bekenstein-Hawking entropy hawking area law black hole dark matter interaction intermediate mass black hole innermost stable circular orbit