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Scientists Discover Way to Send Information into Black Holes Without Using Energy

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How Primordial Black Holes & Dark Matter Might Come From Eternal Inflation?

The mystery of dark matter (DM) may have an extraordinary origin. Franciolini, Peloso, and Riotto propose that DM could come from primordial black holes (PBHs) formed during the universe’s inflationary phase. During inflation, the universe expanded rapidly, and tiny quantum fluctuations created regions with slightly different densities. Most regions stopped inflating and reheated to form ordinary matter. However, rare patches could continue inflating forever. To an outside observer, these eternally inflating regions appear as black holes. If enough of these PBHs formed with asteroid-like masses, they could account for all of dark matter. Unlike traditional PBH formation, which happens after inflation, this mechanism arises naturally from the properties of inflation itself. A key prediction is a stochastic gravitational wave background detectable in the millihertz range by upcoming experiments like LISA, offering a testable signature. This scenario links quantum fluctuations, black holes, and dark matter, suggesting it might literally come from eternity.

One of the most profound mysteries in modern physics is the nature of dark matter (DM), the invisible substance that makes up roughly 27% of the universe. Despite decades of research, we still don’t know what dark matter really is. A new and exciting idea proposed by Franciolini, Peloso, and Riotto suggests that dark matter might originate from one of the fundamental properties of the early universe’s inflationary phase—the possibility that some regions of space might have been “eternally inflating.” These eternally inflating patches, the researchers argue, could appear in our universe as primordial black holes (PBHs), potentially accounting for all of the dark matter we observe today.

Primordial Black Holes: A Dark Matter Candidate

Primordial black holes are hypothetical black holes formed in the very early universe, long before stars or galaxies existed. Unlike regular black holes, which result from collapsing massive stars, PBHs could form from regions of extremely high density caused by fluctuations in the fabric of spacetime during cosmological inflation.

Inflation is a brief but incredibly rapid expansion of the universe that occurred a fraction of a second after the Big Bang. During this phase, tiny quantum fluctuations in the curvature of spacetime became stretched to cosmic scales, creating the seeds for galaxies, clusters, and, possibly, black holes. If some of these fluctuations were large enough, they could collapse under their own gravity to form PBHs.

What makes the proposal by Franciolini, Peloso, and Riotto remarkable is that it relies solely on the natural properties of inflation—without introducing any new exotic particles beyond the Standard Model of particle physics. In this scenario, PBHs could explain all of dark matter, offering a solution to one of physics’ greatest puzzles.

Eternal Inflation and Dark Matter

During inflation, not all regions of space evolve the same way. Most regions eventually stop inflating, reheating to form the matter and radiation we see in our universe. However, some rare patches could continue to inflate forever due to quantum fluctuations. These eternally inflating regions remain hidden behind what is perceived as a black hole horizon, essentially becoming PBHs from the perspective of an outside observer.

Even though these regions are extremely rare, their potential impact is enormous. If their mass falls within a specific range—roughly equivalent to that of an asteroid—PBHs formed this way could constitute the totality of dark matter. This mechanism, sometimes called “DM from eternity,” could produce a higher abundance of PBHs than standard formation processes, which rely on the collapse of overdense regions during the radiation-dominated era of the universe.

How Eternal Inflation Creates Black Holes

The key to this process lies in the fluctuations of the curvature of spacetime. During inflation, these fluctuations vary randomly from region to region. Most patches stop inflating and contribute to ordinary matter, but occasionally, a patch experiences a fluctuation large enough to keep inflating eternally.

Mathematically, this happens when the quantum fluctuations of the inflaton—the hypothetical “clock” driving inflation—become larger than its classical motion. When this occurs, the curvature perturbation, denoted by ζ, exceeds a critical value (ζ ≥ 1). Such regions never stop inflating, and from an external perspective, they appear as black holes.

The probability of these eternally inflating regions existing within our observable universe is small, but because the universe contains an enormous number of such regions, the cumulative effect can be significant. These rare patches could therefore generate a population of PBHs that matches the observed dark matter density.

Mass and Abundance of PBHs from Eternity

The mass of PBHs formed through eternal inflation is determined by the energy contained in a Hubble-sized patch of space at the end of inflation. For a typical scenario, the PBH mass is roughly:

[
M_\text{PBH} \sim 10^{-12} M_\odot
]

where (M_\odot) is the mass of the Sun. This mass falls within a narrow window where PBHs could make up all of dark matter without conflicting with current observational constraints.

The abundance of these PBHs is controlled by the size of the curvature fluctuations. A small variance in the curvature perturbation is enough to generate a population of PBHs that can explain the full dark matter density. This makes the “DM from eternity” scenario both plausible and potentially observable.

A Bonus: Gravitational Waves

An exciting aspect of this mechanism is that it predicts a broad spectrum of stochastic gravitational waves (GWs). These waves are ripples in spacetime produced by the same large fluctuations that create PBHs. If PBHs are indeed formed from eternally inflating regions, we should detect a relatively flat gravitational wave background at frequencies around the millihertz (mHz) range.

Upcoming space-based experiments, such as LISA, could potentially observe this gravitational wave signal, providing a direct test of this bold theory. Detection of such a signal would be a strong hint that some or all of dark matter originates from PBHs formed during eternal inflation.

Comparison to Standard PBH Formation

The traditional mechanism for PBH formation involves the collapse of overdense regions during the radiation-dominated era after inflation. In contrast, PBHs from eternal inflation form directly during the inflationary phase itself, as certain patches fail to reheat. Both processes can contribute to the total PBH population, but the eternal inflation mechanism can dominate if the curvature fluctuations are large enough.

This difference is crucial because it offers a unique pathway to generate the right abundance of PBHs for dark matter, especially in the asteroid-mass range.

Challenges and Future Directions

While the “DM from eternity” idea is compelling, there are several challenges and open questions:

  1. Non-Gaussian Fluctuations: The theory often assumes that curvature perturbations follow a Gaussian distribution. However, at very large fluctuations, this assumption may break down. Exploring non-Gaussian statistics could refine predictions.

  2. PBH Mass Variety: Different inflationary scenarios could produce PBHs with different masses. While asteroid-mass PBHs are ideal for dark matter, heavier PBHs could contribute to black hole mergers observed by gravitational wave detectors like LIGO and Virgo.

  3. Reheating Details: The assumption of instantaneous reheating at the end of inflation simplifies calculations but may not reflect reality. Future models could include more realistic reheating processes.

  4. Observational Tests: Gravitational waves are a key observational signature. Future detectors may confirm or rule out the presence of a stochastic GW background predicted by this scenario.

Conclusion

Franciolini, Peloso, and Riotto’s proposal offers a bold and elegant solution to the dark matter mystery: our universe’s dark matter could be the result of black holes formed from eternally inflating regions of spacetime. If true, this would connect the largest cosmological scales with the smallest, quantum-driven fluctuations in a remarkable way.

This scenario not only provides a potential explanation for the abundance of dark matter but also makes clear predictions for gravitational wave experiments, offering a path for empirical verification. While challenges remain, the idea that dark matter could literally come from eternity is a fascinating glimpse into the deep connections between inflation, black holes, and the unseen mass of our cosmos.

The coming decades of observational astronomy and gravitational wave detection may finally reveal whether these primordial black holes are indeed the universe’s hidden matter—a profound discovery that could reshape our understanding of the cosmos.

Reference: G. Franciolini, M. Peloso, A. Riotto, "Dark Matter from Eternity", Arxiv, 2026. https://arxiv.org/abs/2602.08338


Technical Terms 

  1. Dark Matter (DM) – Invisible matter that makes up most of the universe’s mass but does not emit light or energy, so we detect it only through gravity.

  2. Primordial Black Holes (PBHs) – Hypothetical black holes formed in the very early universe, not from stars, but from dense regions created shortly after the Big Bang.

  3. Cosmological Inflation – A very short period right after the Big Bang when the universe expanded extremely rapidly.

  4. Eternal Inflation – A scenario where some regions of the universe keep inflating forever due to quantum fluctuations.

  5. Curvature Perturbation (ζ) – Tiny variations in the shape or curvature of spacetime during inflation, which can grow into structures like galaxies or black holes.

  6. Reheating – The process after inflation ends when the universe heats up and forms particles like matter and radiation.

  7. Hubble Radius (H⁻¹) – A distance scale in the universe beyond which objects are moving away faster than light due to cosmic expansion.

  8. Schwarzschild Horizon – The boundary of a black hole beyond which nothing, not even light, can escape.

  9. Gravitational Waves (GWs) – Ripples in spacetime caused by massive objects moving or by fluctuations in the early universe.

  10. Radiation-Dominated Era – The period in the early universe when radiation (light and particles) was the main contributor to the universe’s energy density.

  11. Quantum Fluctuations – Tiny random changes in energy or fields at very small scales, caused by quantum mechanics.

  12. Asteroid-like Mass – Very small mass for a black hole, comparable to that of a large asteroid, rather than a star.

  13. Stochastic Background – A random, continuous signal made up of many overlapping sources, such as gravitational waves from the early universe.

  14. Gaussian Distribution – A common way to describe random variations, shaped like a bell curve.

  15. Overdensity – A region in space where matter is denser than average, which can collapse to form a black hole.

  16. Comoving Size – A distance measure in the universe that stays constant with the expansion of space.

  17. Inflaton – A hypothetical field responsible for driving cosmic inflation.

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