Low Energy Galactic Neutrinos Rule Out Dark Matter Within 292 Kpc

Scientists are investigating the elusive nature of low-energy galactic neutrinos, seeking to understand whether these particles could unlock secrets about dark matter and fundamental forces. Led by Eduardo Flores, Elise Cantu, and Ian Marano, all from Rowan University, alongside Osvan Vivar-Garcia, Shabhaz Khalandar et al, this research presents compelling evidence exploring two distinct theoretical frameworks for neutrino interaction, one involving a long-range force mediated by gravitons and the other stemming from spacetime curvature. Their calculations demonstrate that, while a long-range interaction doesn’t support neutrinos as a primary dark matter component, the detection of a predicted bound neutrino structure would confirm the existence of this novel force. Crucially, the study reveals that under conditions of spacetime curvature, neutrinos can behave as viable dark matter candidates, potentially even offering a solution to the long-standing matter-antimatter asymmetry puzzle , a truly significant step forward in astroparticle physics.

Neutrinos probe quantum gravity and dark matter

Scientists have unveiled a groundbreaking study of low-energy galactic Neutrinos, demonstrating their potential as a sensitive probe of the fundamental nature of gravity itself. The team achieved a detailed analysis of neutrino behaviour under these contrasting gravitational models, calculating mass distributions and interaction probabilities to assess their viability as dark matter candidates. The study initially considered the possibility of gravity being a quantum interaction, leading to the prediction of a bound neutrino structure akin to an atom, stabilised by the exchange of virtual gravitons.
Calculations revealed that within a radius of 292 kiloparsecs, the total mass of this structure accounts for only 10−29 of the galaxy’s dark matter, effectively ruling it out as a primary dark matter constituent. However, the researchers emphasise that experimental confirmation of this bound structure would provide direct evidence for gravity operating as a quantum force mediated by gravitons, a significant breakthrough in theoretical physics. This work establishes a clear pathway for testing fundamental aspects of gravity through neutrino detection. Alternatively, the research explored the scenario where gravity arises from spacetime curvature, as described by general relativity.

In this regime, neutrinos interact solely via the weak force, becoming effectively collisionless and behaving as free classical particles orbiting the galaxy without experiencing Fermi pressure. The team demonstrated, using the Vlasov equation, that such a population of neutrinos could be sufficiently compact to reproduce the observed Milky Way rotation curve, thereby presenting neutrinos as a viable, albeit unconventional, dark matter candidate. This finding challenges conventional dark matter models and opens new avenues for investigation. Furthermore, the extremely small cross-section for neutrino-antineutrino annihilation suggests a near-equilibrium state between these particles, potentially offering a solution to the long-standing mystery of the matter-antimatter asymmetry in the universe.

Experiments show that low-energy galactic neutrinos, with masses less than or equal to 0.4eV/c2, are nearly undetectable due to their low energies and the short range of the weak interaction, yet their sheer abundance could have profound cosmological implications. The team calculated a degeneracy term of 4 × 105, indicating a completely degenerate Fermi gas, and a mean free path of 1.6 × 1020 metres, highlighting the neutrinos’ tendency to travel vast distances without interaction. This detailed analysis provides a compelling case for revisiting light neutrinos as potential dark matter candidates, particularly in light of recent developments concerning virtual particles and their role in particle interactions.

Neutrino Structures and Quantum Gravity Tests offer promising

Scientists investigated low-energy galactic neutrinos under two distinct gravitational models to determine their potential role in dark matter and probe the fundamental nature of gravity. The research team computed the mass distribution of a hypothesised bound neutrino structure arising from a quantum gravitational interaction, finding a total mass within 292 kpc to be only 10−29 of the galaxy’s dark matter, effectively excluding it as a viable dark matter candidate. Nevertheless, the study asserts that confirming this structure would provide direct evidence for gravity being mediated by gravitons, serving as a potential ‘smoking-gun’ signature of quantum gravity. Should gravity instead emerge from spacetime curvature, the researchers posited neutrinos would behave as collisionless classical particles orbiting the galaxy.

Experiments employed a statistical orbital framework, combining statistical methods with orbital mechanics, to model neutrino behaviour and derive the mass distribution consistent with observed galactic rotation curves. The team meticulously calculated the average neutrino energy, revealing it to be negative over most radii, a physically consistent characteristic of bound particles in orbit, as depicted in Figure 7b. Furthermore, the study pioneered a detailed analysis of neutrino velocities, demonstrating a rapid change with radius in regions of regular mass, reaching speeds measured in km/s, as shown in Figure 7a. The work harnessed the extremely small neutrino-antineutrino annihilation cross section to suggest near-equilibrium between these particles, potentially resolving the matter-antimatter asymmetry observed in the universe.

This innovative approach enables the exploration of a non-quantum gravity framework where free classical neutrinos remain a viable dark matter candidate. Crucially, the research demonstrates that even rare interactions between neutrinos and baryonic matter can mediate sufficient energy exchange to reproduce the observed Milky Way rotation curve. The team’s calculations, detailed in the published work, suggest that a substantial fraction of these neutrinos could be antineutrinos, potentially explaining the scarcity of antimatter and hinting at physics beyond the Standard Model. This study, therefore, establishes low-energy neutrinos as a critical intersection of cosmology, particle physics, and gravitation, offering testable consequences linking galactic dynamics to fundamental physics.

Neutrino Bounds Constrain Long-Range Gravity Models effectively

Scientists have demonstrated that low-energy galactic neutrinos offer a sensitive probe into the fundamental nature of gravity. The research team investigated two distinct descriptions of gravitational interaction, revealing crucial insights into neutrino behaviour and potential dark matter candidates. Experiments revealed that if gravity operates as a long-range interaction, neutrinos can form an atom-like bound structure; however, calculations show that within a radius of 292 kpc, the total mass of this structure accounts for only 10−29 of the galaxy’s dark matter, effectively ruling it out as a primary dark matter constituent. Nevertheless, confirmation of this structure would provide direct evidence for gravity being a force mediated by gravitons.

Alternatively, if gravity arises from spacetime curvature, neutrinos interact solely via the weak force and behave as collisionless classical particles orbiting the galaxy, experiencing no Fermi pressure. Results demonstrate that this population can be sufficiently compact to accurately reproduce the observed Milky Way rotation curve, establishing neutrinos as viable dark matter candidates. The team measured an extremely small neutrino-antineutrino annihilation cross section, implying near-equilibrium between neutrinos and antineutrinos, potentially resolving the matter-antimatter asymmetry puzzle. To model the neutrino halo, researchers employed Euler’s equation and an equation of state relating density, pressure, and velocity dispersion.