The Potential of Long-Lived Primordial Black Holes as Dark Matter and Astrophysical Particle Accelerators

Concetti Chiave

Light primordial black holes (PBHs) may still exist as dark matter candidates due to the memory burden effect, and their mergers could produce detectable ultrahigh-energy cosmic rays.

Sintesi

• Bibliographic Information: Zantedeschi, M., & Visinelli, L. (2024). Memory-Burdened Primordial Black Holes as Astrophysical Particle Accelerators. arXiv preprint arXiv:2410.07037v1.

• Research Objective: This research paper investigates the observational consequences of the memory burden effect on primordial black holes (PBHs) and their potential as dark matter candidates.

• Methodology: The authors utilize theoretical models, including the holographic description of black holes and the black hole N-portrait, to analyze the impact of the memory burden effect on PBH evaporation. They calculate the merger rate of PBH binaries and estimate the resulting flux of particles, such as gamma rays and neutrinos, using numerical simulations and the BlackHawk code.

• Key Findings: The study reveals that the memory burden effect could allow PBHs with masses below the traditional evaporation limit to persist until the present day, potentially constituting a fraction of dark matter. Mergers of these PBHs would create "young" black holes that emit high-energy particles, leading to detectable signatures in cosmic ray, gamma-ray, and neutrino observations. The authors find that current neutrino flux measurements from IceCube are in tension with light PBHs as the sole component of dark matter within a specific mass range.

• Main Conclusions: The research suggests that the memory burden effect has significant implications for our understanding of PBH evolution and their potential role as dark matter. The authors propose that observations of ultrahigh-energy cosmic rays, gamma rays, and neutrinos could provide crucial evidence for the existence of these long-lived PBHs.

• Significance: This study contributes to the ongoing search for dark matter and offers a novel perspective on the behavior of black holes. The findings have the potential to advance our understanding of fundamental physics and the early universe.

• Limitations and Future Research: The authors acknowledge that the precise details of the memory burden effect and its impact on PBH evolution require further theoretical investigation. Additionally, more precise measurements of cosmic ray, gamma-ray, and neutrino fluxes from future observatories are crucial to confirm or refute the presence of these memory-burdened PBHs.

Statistiche

PBHs with a mass of approximately 10^8 grams could be viable dark matter candidates while satisfying known constraints.
For a specific parameter (k=1), memory-burdened BHs as light as 3 x 10^3 grams can be dark matter candidates.
Current measurements of the isotropic neutrino flux at Earth are in tension with light PBHs as DM candidates within the mass range 7 × 10^3 ≲mPBH/g ≲4 × 10^8, if neutrinos are of Majorana nature.

Citazioni

"The memory burden effect, stating that the amount of information stored within a system contributes to its stabilization, is particularly significant in systems with a high capacity for information storage such as black holes."
"In this scenario, we demonstrate that their mergers would continue to occur today, leading to the formation of “young” black holes that resume evaporating, producing ultrahigh-energy cosmic rays detectable by current experiments."
"The emission spectrum would be thermal in all Standard Model particle species, offering a clear and distinguishable signature."

Approfondimenti chiave tratti da

Memory-Burdened Primordial Black Holes as Astrophysical Particle Accelerators

by Michael Zant... alle arxiv.org 10-10-2024

https://arxiv.org/pdf/2410.07037.pdf

Domande più approfondite

How would the detection of Hawking radiation from these long-lived PBHs further support or challenge our current understanding of black hole thermodynamics?

Answer: Detecting Hawking radiation from these long-lived PBHs would be a groundbreaking discovery with profound implications for our understanding of black hole thermodynamics. Here's how:
Support for Black Hole Thermodynamics:

Confirmation of Hawking's Theory: The detection would serve as direct confirmation of Hawking's theory of black hole evaporation, a cornerstone of black hole thermodynamics. It would validate the idea that black holes are not entirely black but emit radiation due to quantum effects near their event horizon.
Evidence for Quantum Processes in Gravity: Hawking radiation arises from the interplay of quantum mechanics and general relativity. Observing it would provide compelling evidence for the quantization of gravity, a long-sought goal in theoretical physics.
Verification of Black Hole Temperature and Entropy: The spectrum of Hawking radiation is directly related to the black hole's temperature, which in turn is linked to its entropy through the laws of black hole thermodynamics. Measuring the spectrum would allow us to verify these fundamental relationships.
Challenges to Current Understanding:

Impact of the Memory Burden Effect: The paper you provided discusses the "memory burden" effect, which could significantly alter the evaporation process, particularly for primordial black holes. Detecting Hawking radiation from these objects would allow us to study this effect directly and potentially refine our models of black hole evaporation.
New Physics Beyond the Standard Model: The properties of the observed Hawking radiation, such as its spectrum and intensity, could provide hints of new particles or interactions beyond the Standard Model of particle physics. Deviations from expected behavior could point towards new physics at play.
Rethinking the Information Paradox: The information paradox arises from the apparent conflict between the unitary evolution of quantum mechanics and the seemingly irreversible loss of information as objects fall into a black hole. Observing Hawking radiation and potentially decoding information encoded within it could shed light on this paradox and lead to a more complete understanding of black hole information storage and retrieval.

Could alternative dark matter models, such as weakly interacting massive particles (WIMPs), also explain the observed neutrino flux without invoking the memory burden effect?

Answer: While weakly interacting massive particles (WIMPs) have long been a favored candidate for dark matter, they face challenges in explaining the observed neutrino flux without additional modifications or assumptions. Here's why:

WIMP Annihilation: WIMPs are theorized to annihilate with each other, producing Standard Model particles, including neutrinos, as byproducts. However, the expected neutrino flux from WIMP annihilation in the galactic halo is generally too low to account for the observed flux by IceCube, especially at high energies.
Constraints from Other Searches: Direct and indirect detection experiments searching for WIMPs have placed stringent limits on their interaction cross-sections and masses. These constraints further limit the possible contribution of WIMP annihilation to the observed neutrino flux.
Alternative Production Mechanisms: Some models propose alternative production mechanisms for WIMPs, such as decay or interactions with other particles, which could potentially enhance the neutrino flux. However, these models often require fine-tuning or introduce additional theoretical complexities.
In contrast to WIMPs, the memory-burdened PBH scenario offers a more natural explanation for the observed neutrino flux:

Direct Hawking Radiation: The evaporation of newly formed black holes from memory-burdened PBH mergers directly produces a flux of neutrinos with a specific energy spectrum, potentially aligning with observations.
Testable Predictions: The PBH scenario makes specific predictions about the energy spectrum, flavor composition, and anisotropy of the neutrino flux, which can be tested with future neutrino observatories.

If the memory burden effect does influence the lifespan of black holes, what are the implications for the long-term fate of the universe and the information paradox?

Answer: If the memory burden effect significantly extends the lifespan of black holes, it has profound implications for the long-term fate of the universe and our understanding of the information paradox:
Long-Term Fate of the Universe:

Black Hole Domination: In a universe dominated by matter and radiation, black holes eventually evaporate due to Hawking radiation. However, if the memory burden effect slows down or halts evaporation, black holes could become a dominant component of the universe's energy density in the distant future.
Altered Expansion History: The presence of long-lived black holes would affect the universe's expansion rate and could alter the transition between different cosmological eras.
Implications for Cyclic Models: Some cosmological models propose cyclic universes that undergo repeated cycles of expansion and contraction. The existence of long-lived black holes could impact the dynamics of these cycles and the fate of information across different epochs.
Information Paradox:

Prolonged Information Storage: If black holes retain information due to the memory burden effect, it implies that information is not lost during black hole evaporation but rather stored for extended periods.
Potential for Information Retrieval: The eventual decay or interaction of these long-lived black holes could release the stored information, potentially resolving the information paradox.
New Insights into Quantum Gravity: Understanding how information is stored and potentially retrieved from memory-burdened black holes could provide valuable insights into the nature of quantum gravity and the relationship between quantum mechanics and spacetime.
Overall, the memory burden effect, if confirmed, would necessitate a reevaluation of our current understanding of the universe's long-term evolution and the fate of information within it. It highlights the interconnectedness of black hole physics, cosmology, and fundamental questions about the nature of information and quantum gravity.