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Zenodo
2026
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| Acceso en línea: | https://doi.org/10.5281/zenodo.19590380 |
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- <p><strong>Title:</strong> Dark Matter Annihilation in Black Hole Adiabatic Spikes: A 2.12 MeV Line Prediction</p> <p><strong>Author:</strong> Alexander Novickis (alex.novickis@gmail.com)</p> <p>We compute the expected dark matter annihilation signal from adiabatic density spikes around supermassive black holes within the Hopf soliton framework, assuming the compact soliton picture of Paper VI [1]. The dark matter mass $m_{\text{DM}} = 2.12$ MeV predicts a monochromatic annihilation line at $E_\gamma = m_{\text{DM}} = 2.12$ MeV from the process DM + DM $\to 2\gamma$. In the smooth NFW halo, the predicted flux is approximately three orders of magnitude below INTEGRAL/SPI sensitivity. However, the adiabatic growth of the central black hole compresses the surrounding dark matter into a steep density spike $\rho \propto r^{-7/3}$ (Gondolo & Silk 1999 [2]), enhancing the annihilation rate $\Gamma \propto \rho^2$ by factors of $10^{12}$--$10^{20}$ within the inner parsec. We compute the spike-enhanced annihilation flux from Sgr A<i>, intermediate-mass black hole candidates, and the Andromeda SMBH M31</i>, and compare with INTEGRAL/SPI sensitivity and the upcoming COSI mission [7]. The annihilation timescale in the spike core sets a maximum density (the "annihilation plateau"), which we compute self-consistently. If the Sgr A* spike survives stellar dynamical heating --- an open astrophysical question --- the 2.12 MeV line may be within reach of COSI (launching ~2027). The line energy is derived from first principles with zero free parameters, and is spectrally isolated from all known nuclear gamma-ray lines. We note an important caveat: Paper LXVII [8] argues that compact $H = 0$ knotted solitons are quantum-mechanically unstable ($\tau \sim 10^{-22}$ s), which would preclude the annihilation channel assumed here. Detection of this line by COSI would simultaneously confirm the compact soliton picture and falsify the vacuum condensate interpretation.</p> <p>Key results include:</p> <ul> <li>Topological DM (m = 2.12 MeV) annihilates via DM + DM → 2γ at E_γ = 2.12 MeV (conditional on Paper VI compact soliton picture; see caveat below)</li> <li>In the smooth NFW halo, the signal is ~3 orders of magnitude below INTEGRAL sensitivity</li> <li>Adiabatic density spikes around supermassive black holes enhance ρ_DM by factors of 10⁶--10¹⁰, and the annihilation rate scales as ρ²</li> <li>The Sgr A* weakened spike may bring the 2.12 MeV line into range of COSI (~2027)</li> <li>The line energy is derived from first principles with zero free parameters</li> <li>Spectrally distinct from all known nuclear lines (nearest: 2.223 MeV neutron capture, 103 keV separation, resolvable at ~30$\times$ SPI spectral resolution)</li> </ul> <p><strong>Keywords:</strong> physics, dark matter, black hole, spectral line, annihilation, soliton, Hopf, INTEGRAL, COSI</p> <p><strong>Series:</strong> Paper LXXXIX in the Hopf Soliton Programme</p>