Dark Matter’s Hidden Link to the Matter-Antimatter Puzzle

Author: Denis Avetisyan

A novel framework proposes that dark matter is composed of stable quark-antiquark nuggets, their abundance directly tied to the observed imbalance between matter and antimatter in the universe.

The emergence of axions, hypothetical particles proposed to resolve fundamental problems in quantum chromodynamics, is understood to be intrinsically linked to the earliest moments of the universe, originating in the aftermath of the Big Bang and continuing through the epoch of the QCD transition-a period marking a critical shift in the state of matter.

This review explores the QCD-AQN framework, detailing the formation of axion-stabilized quark nuggets and their potential as a unified explanation for dark matter and baryon asymmetry.

The enduring mysteries of dark matter and the matter-antimatter asymmetry demand novel theoretical approaches. This paper, ‘QCD-driven dark matter: AQNs formation and observational tests’, introduces the QCD-AQN framework, positing that dark matter comprises dense aggregates of quarks and antiquarks-specifically, ‘AQNs’-stabilized by axion domain walls. This framework uniquely links the abundance of dark matter to the observed baryon asymmetry, offering a unified explanation for both phenomena. Could this QCD-based scenario not only resolve the dark matter puzzle but also illuminate the nature of dark energy itself?

The Enigma Deepens: Beyond Conventional Dark Matter

While the Standard Cosmological Model remarkably explains the large-scale structure of the universe and the cosmic microwave background, its attempts to incorporate dark matter face persistent challenges. Observations of galactic rotation curves, gravitational lensing, and the distribution of matter in galaxy clusters reveal a substantial amount of missing mass – approximately 85% of the universe’s total matter content – that cannot be accounted for by visible matter or known particles. This discrepancy isn’t merely a matter of refining existing parameters; it suggests the Standard Model of particle physics, which underpins the cosmological model, is incomplete. Consequently, physicists are actively pursuing extensions to this model, exploring possibilities like weakly interacting massive particles (WIMPs), axions, sterile neutrinos, and even primordial black holes, each representing a potential dark matter candidate and a pathway to uncover the new physics required to resolve this enduring cosmic puzzle.

Despite decades of dedicated effort, experiments designed to directly detect dark matter interactions remain inconclusive. These searches, often utilizing ultra-sensitive detectors shielded deep underground to minimize background noise, have established increasingly stringent limits on the properties of potential dark matter particles. The continued absence of a definitive signal suggests that the simplest dark matter candidates – Weakly Interacting Massive Particles (WIMPs) – may not fully account for the observed dark matter abundance. Consequently, theoretical physicists are actively exploring a broader range of possibilities, including axions, sterile neutrinos, and primordial black holes, as well as more complex interaction models that go beyond the Standard Model of particle physics. This pursuit necessitates innovative experimental strategies and a re-evaluation of fundamental assumptions about the nature of dark matter itself, pushing the boundaries of both theoretical and experimental physics.

The universe appears to contain roughly five times more dark matter than ordinary matter, a discrepancy quantified by a measured density of 0.120 h². This precise value, derived from observations of the cosmic microwave background and large-scale structure, poses a considerable hurdle for established particle physics models, as the Standard Model fails to provide a suitable candidate with the necessary properties to account for such abundance. Consequently, theoretical physicists are actively investigating a diverse range of beyond-the-Standard-Model particles – including weakly interacting massive particles (WIMPs), axions, sterile neutrinos, and even primordial black holes – each possessing unique characteristics and interaction mechanisms that could potentially resolve the dark matter puzzle and align theoretical predictions with observational data. The ongoing search isn’t merely about finding a particle, but determining which, if any, of these novel candidates accurately reflects the composition of the unseen universe.

New high-resolution imaging of the Bullet Cluster, combining data from the James Webb Space Telescope and Chandra X-ray Observatory, confirms the presence of a dominant dark matter component by separating the distribution of mass (inferred from gravitational lensing, shown in blue) from the hot gas (shown in pink) resulting from the merging clusters.

A Novel Framework: Quark-Antiquark Networks and Axionic Stabilization

The QCD-AQN framework postulates that dark matter is comprised of dense, gravitationally bound aggregates of quarks and antiquarks. This offers a distinct alternative to Weakly Interacting Massive Particle (WIMP) candidates, which have faced increasing scrutiny from direct detection experiments. These quark-antiquark aggregates are predicted to have masses ranging from $10^{-{12}}$ to $10^{-9}$ solar masses, differing significantly from the typical WIMP mass range. The formation of these aggregates occurs in the early universe through mechanisms related to Quantum Chromodynamics (QCD), specifically involving the confinement of quarks and the resulting formation of stable, multi-quark states. Unlike WIMPs, which rely on weak interactions for detection, the QCD-AQN model predicts a population of macroscopic objects detectable through gravitational lensing or potential interactions with stellar systems.

Axion Domain Walls are topological defects formed due to the non-trivial topology of the Axion field, a hypothetical particle proposed to solve the strong CP problem in quantum chromodynamics. These walls represent boundaries between regions with different Axion field orientations and possess a surface tension that provides a stabilizing force against the dispersal of Quark-Antiquark Aggregates. Specifically, the energy density associated with the Domain Walls creates a potential well that confines the aggregates, preventing their decay over cosmological timescales. The stability is directly related to the Axion decay constant; a smaller decay constant results in a higher surface tension and thus, more robust confinement of the aggregates. This mechanism ensures the longevity of the dark matter candidates, addressing a key challenge for alternative models beyond Weakly Interacting Massive Particles (WIMPs).

The QCD-AQN framework proposes a direct correlation between dark matter density and the observed Matter-Antimatter Asymmetry. Baryogenesis, the process creating the asymmetry, is theorized to have generated a comparable density of stable, non-baryonic dark matter in the form of Quark-Antiquark Aggregates stabilized by Axion Domain Walls. Specifically, the model posits that the same physics responsible for producing the excess of matter over antimatter in the early universe also generated the observed dark matter relic abundance, thereby offering a unified explanation for both cosmological puzzles without requiring separate, arbitrary parameters for each. This linkage avoids the need for fine-tuning often encountered in models treating dark matter and the asymmetry as unrelated phenomena.

The architecture of the <span class="katex-eq" data-katex-display="false">\overline{AQN}</span> network consists of a structured arrangement of emission sources, as detailed in [2013arXiv1305.6318L]. — The architecture of the $\overline{AQN}$ network consists of a structured arrangement of emission sources, as detailed in [2013arXiv1305.6318L].

The Foundations: Quantum Chromodynamics and the Axion’s Role

Quantum Chromodynamics (QCD) describes the strong force, one of the four fundamental forces in nature, governing the interactions between quarks and gluons. Quarks, possessing fractional electric charges, are never observed in isolation due to a phenomenon known as color confinement. Instead, they combine to form hadrons, which are composite particles including baryons (three quarks) and mesons (quark-antiquark pairs). The strong force, mediated by gluons, ensures that these quark-antiquark aggregates are stable despite the repulsive electromagnetic force between similarly charged quarks. The mathematical framework of QCD, based on $SU(3)$ gauge symmetry, predicts the properties of hadrons and their interactions, and is essential for understanding the structure of matter at the subatomic level.

The axion, postulated as a solution to the strong CP problem within Quantum Chromodynamics (QCD), is theorized to stabilize quark-antiquark aggregates via domain wall formation. These domain walls arise from a non-zero vacuum expectation value of the axion field and represent topological defects in the field configuration. The energy density concentrated within these walls provides a stabilizing force, preventing the decay of the aggregates into lower-energy states. The existence and properties of axions, and consequently the stabilization mechanism, are dependent on the specific parameters of the QCD axion model, including the axion mass and decay constant. Current research focuses on detecting these axions through various experimental methods, which would confirm their role in both dark matter composition and aggregate stability.

The proposed framework, linking Quantum Chromodynamics (QCD) and axion physics, addresses the strong CP problem by introducing the axion as a pseudo-Nambu-Goldstone boson arising from the spontaneous breaking of an approximate U(1) symmetry. This symmetry is proposed to solve the strong CP problem, which concerns the observed absence of an electric dipole moment in the neutron, despite theoretical predictions of its existence due to CP-violating terms in the QCD Lagrangian. The axion’s interactions dynamically cancel these terms, effectively setting them to zero. Furthermore, the same theoretical properties that make the axion a solution to the strong CP problem also establish it as a viable candidate for dark matter, possessing the appropriate abundance and interaction strength to explain observed cosmological phenomena.

Cosmological Harmony: Baryonic and Dark Matter Densities

The prevailing cosmological model, built upon the QCD-AQN framework, posits a fundamental connection between the abundance of ordinary, or baryonic, matter and the enigmatic dark matter that dominates the universe. This isn’t merely a coincidental correlation; rather, the framework naturally predicts a specific relationship between these densities, stemming from the underlying physics governing the early universe and the transition phases of quantum chromodynamics. Crucially, this predicted relationship aligns remarkably well with observational data-measurements of baryon density, currently estimated around 0.0224 $h^2$ , are consistent with the density of dark matter inferred from sources like the Cosmic Microwave Background and gravitational lensing studies. This consistency provides compelling support for the QCD-AQN framework, suggesting a deeper, intrinsic link between the visible and invisible components of the cosmos – a connection that transcends simple coincidence and points towards a unified physical origin.

The universe exhibits a striking symmetry in the densities of ordinary, or baryonic, matter and dark matter, a phenomenon the QCD-AQN framework elegantly explains. This isn’t merely a coincidence; the model predicts a natural connection between these two fundamental components of the cosmos. Current measurements indicate a baryon density of approximately 0.0224 h², where ‘h’ represents the Hubble constant, signifying the rate of the universe’s expansion. The remarkable aspect is that the density of dark matter is observed to be within the same order of magnitude, suggesting a deeper, underlying physical reason for their proximity – a reason the QCD-AQN framework proposes through its unique theoretical underpinnings and provides a compelling explanation for this observed balance in the universe’s composition.

Cosmological models predicting a link between ordinary matter and dark matter find strong corroboration through detailed mapping of the universe. Observations of the Cosmic Microwave Background – the afterglow of the Big Bang – reveal subtle temperature fluctuations that reflect the distribution of matter, both visible and dark, in the early universe. These patterns, meticulously analyzed, align with predictions derived from the QCD-AQN framework. Further bolstering this consistency are studies utilizing Gravitational Lensing, where the path of light from distant galaxies is bent by the gravity of intervening matter. By charting the distortions in these light paths, astronomers can reconstruct a three-dimensional map of dark matter distribution, a map which remarkably echoes the predictions based on baryon density and the established cosmological model. This convergence of evidence from distinct observational techniques offers compelling support for a universe where the densities of ordinary and dark matter are intrinsically connected.

The allowed parameter space for axion mass <span class="katex-eq" data-katex-display="false">m_a</span> and inflationary Hubble scale <span class="katex-eq" data-katex-display="false">H_I</span> is constrained by isocurvature observations, dark matter saturation, and stellar energy loss, resulting in a broader range for the pre-inflationary scenario (left) and a narrow range for the post-inflationary scenario (right). — The allowed parameter space for axion mass $m_a$ and inflationary Hubble scale $H_I$ is constrained by isocurvature observations, dark matter saturation, and stellar energy loss, resulting in a broader range for the pre-inflationary scenario (left) and a narrow range for the post-inflationary scenario (right).

Future Pathways: Towards Direct Detection and Confirmation

Ongoing investigations are dedicated to bolstering the predictive power of this dark matter framework, specifically geared toward direct detection experiments. Researchers are currently refining the model’s parameters and simulating potential event signatures within detectors, aiming to distinguish signals originating from axion-like particles from background noise. This involves exploring a wider range of masses and interaction strengths, and incorporating more realistic detector responses. By generating concrete, testable predictions, this work seeks to guide the design and analysis of future experiments, ultimately enabling a definitive search for these elusive particles and providing crucial insights into the composition of the universe.

The proposed dark matter framework isn’t built in a vacuum; its parameters are rigorously tested against existing astrophysical observations. Specifically, analyses of the Bullet Cluster – a system formed from the collision of two galaxy clusters – place limits on the self-interaction strength of these Axion-like Quasi-Particles (AQNs). The observed separation of dark matter from the baryonic matter during the collision requires a limited degree of self-interaction, a condition the model readily accommodates. Furthermore, constraints from Big Bang Nucleosynthesis – the formation of light elements in the early universe – refine the allowable mass range and abundance of AQNs, ensuring the model aligns with established cosmological parameters. These independent checks, leveraging data from vastly different sources, bolster the framework’s viability and guide ongoing refinements to its predictive power.

Current research significantly narrows the potential mass of Axion-like Quark Nuggets (AQNs), positioning them within the remarkably constrained range of 1 to 1000 grams. This determination arises from a convergence of data: observations from the IceCube Neutrino Observatory, which limits AQN production rates, geothermal constraints on heat flow within the Earth, and broader observational data regarding dark matter abundance. Establishing this mass range is pivotal, as it opens avenues for designing dedicated dark matter detection experiments capable of identifying these unique particles. Furthermore, this framework suggests that AQNs, if confirmed, could fundamentally reshape understandings of dark matter’s composition and its influence on cosmic structures and the universe’s overall evolution – moving beyond the limitations of weakly interacting massive particles (WIMPs) and offering a compelling alternative for solving one of cosmology’s most enduring mysteries.

The pursuit of a unified cosmological model, as evidenced in this QCD-AQN framework, inherently challenges established paradigms. It posits a dark matter candidate-quark-antiquark nuggets stabilized by axion domain walls-that elegantly ties dark matter abundance to the observed matter-antimatter asymmetry. This willingness to dismantle conventional thinking echoes the sentiments of Paul Feyerabend, who once stated, “Anything goes.” The framework doesn’t shy away from proposing radical solutions, accepting that established methodologies may prove insufficient in explaining the universe’s deepest mysteries. Like all systems, cosmological models are subject to decay and revision; this work embraces that impermanence, suggesting that time isn’t a constraint but the very medium in which understanding evolves.

The Horizon of Refinement

The QCD-AQN framework, positing dark matter as stabilized quark nuggets bound by axion domain walls, offers a compelling, if provisional, bridge between the matter-antimatter asymmetry and the unseen universe. Every failure to detect axions directly, or to fully reconcile predicted and observed dark matter densities, is a signal from time – a reminder that elegance in theory does not guarantee fidelity to reality. The immediate horizon lies in refining the modeling of AQN formation; the precise conditions for nugget stability, and the distribution of masses, remain open questions. A crucial test will be the ability to predict observable signatures-not simply a detection event, but a statistically significant distribution of events-from potential gravitational lensing or microlensing studies.

The linking of dark matter abundance to baryogenesis, while conceptually attractive, demands rigorous scrutiny. Alternative mechanisms for both phenomena continue to emerge, and the QCD-AQN model must demonstrate a resilience to these competing explanations. Refactoring this dialogue with the past requires a more complete understanding of the QCD phase diagram at cosmological epochs, and a detailed assessment of the impact of initial conditions on AQN formation rates.

Ultimately, the true measure of this framework-as with all cosmological models-will be its capacity to gracefully accommodate future observations. Time is not a metric to be conquered, but the medium in which systems either decay or endure. The persistent pursuit of consistency-between theory, simulation, and experiment-is not merely a scientific endeavor; it is an acknowledgement of the inevitable, and a testament to the enduring power of informed speculation.

Original article: https://arxiv.org/pdf/2603.15585.pdf

Contact the author: https://www.linkedin.com/in/avetisyan/