For the first time, researchers at Hiroshima University’s International Institute for Sustainability with Knotted Chiral Meta Matter (WPI-SKCM²), led by Professor Muneto Nitta, alongside collaborators at Keio University and Deutsches Elektronen-Synchrotron in Germany, have demonstrated that topologically knotted field configurations can naturally arise during the early, turbulent moments following the Big Bang. Their study, recently published in Physical Review Letters, suggests these “cosmic knots” may have briefly dominated the primordial cosmos, undergoing collapse processes that favored the production of matter over antimatter—a phenomenon elusive to observation but potentially traceable via gravitational wave signatures detectable by upcoming observatories.

The intellectual quandary tackled by this work is known as baryogenesis—the puzzle that, according to the Standard Model of particle physics, the Big Bang should have created matter and antimatter in equal quantities. Given that matter and antimatter annihilate upon contact, the universe should have been left flat, populated solely by radiation. Contrary to this, a slight preponderance of matter survived, one particle per billion matter-antimatter pairs, giving rise to everything we observe today. This scarcity defies Standard Model predictions, which underestimate the asymmetry’s magnitude by several orders of magnitude, compelling physicists to search beyond classical paradigms for viable mechanisms.

The team’s innovative approach synthesizes two pivotal symmetries beyond the Standard Model: the gauged Baryon Number Minus Lepton Number (B−L) symmetry and the global Peccei–Quinn (PQ) symmetry. Each addresses longstanding theoretical challenges. The B−L symmetry furnishes a natural explanation for neutrino masses via the inclusion of heavy right-handed neutrinos, while the PQ symmetry, introduced to solve the strong CP problem, predicts the axion, an eminent dark matter candidate. By gauging the B−L symmetry and preserving the global PQ symmetry, the researchers uncovered a fertile ground for topological constructs to emerge, bringing together magnetic flux tubes and superfluid vortices into energetically stable, knotted configurations known as knot solitons.

These knot solitons arise from the interplay of distinct phase transitions in the early universe. The breaking of the B−L symmetry generates magnetic flux tube strings—line-like defects threading through spacetime—while the spontaneously broken PQ symmetry produces flux-free superfluid vortices. Remarkably, the coupling between these two types of defects imparts a superconducting quality to the flux tubes and creates a metastable intertwined structure that resists conventional decay mechanisms. This topological locking lends the knots stability, allowing them to persist in a “knot-dominated era,” during which their energy density surpasses that of the surrounding radiation field.

Unlike radiation, whose energy density dilutes rapidly as the universe expands, the energy residing in these knot solitons diminishes more slowly, behaving like matter. Consequently, they folded into cosmic history a transient epoch wherein these intricate knots temporarily governed the energy budget of the universe. This era concluded when quantum tunneling—a counterintuitive quantum mechanical phenomenon permitting particles to surmount otherwise insurmountable energy barriers—enabled the knots to untangle and collapse. The decay process emitted copious heavy right-handed neutrinos, which then underwent asymmetric decays favoring matter over antimatter, injecting the cosmic inventory with a subtle imbalance that ultimately seeded all baryonic matter.

This cascade of events is deeply woven into the model’s mathematical architecture. Calculations account for the formation efficiency of knots, the mass scale of the heavy right-handed neutrinos (estimated around 10¹² GeV), and the resultant reheating temperature of approximately 100 GeV—a critical threshold corresponding to the final epoch when electroweak processes can transmute neutrino asymmetries into baryon asymmetries. This congruence with known physical scales boosts confidence in the model’s naturalness and explanatory power.

Moreover, the collapse of these cosmic knots leaves a distinct imprint on spacetime itself. The sudden disappearance of massive topological structures should have released gravitational waves with characteristic frequencies and intensities. The shape of the gravitational-wave spectrum would diverge significantly from standard cosmological backgrounds, potentially detectable by next-generation observatories such as the European Laser Interferometer Space Antenna (LISA), the U.S.-based Cosmic Explorer, and Japan’s Deci-hertz Interferometer Gravitational-wave Observatory (DECIGO). These facilities could, for the first time, listen in on echoes from a knot-dominated era, a rare empirical foothold into the enigmatic processes that set the matter-antimatter asymmetry.

Fundamentally, the concept of cosmic knots as topological solitons is profound. Solitons represent field configurations defined by invariants impervious to continuous deformation, ensuring stability despite the expanding and dynamic nature of the cosmos. This topology confers robustness to the proposed knot structures, insulating their theoretical existence from many variations in model parameters and making their predicted cosmological role compelling.

The researchers emphasize that while Kelvin’s original intuition—that atoms themselves might be knots—did not withstand the scrutiny of modern atomic physics, their work revitalizes knot theory in the context of cosmology and particle physics. Instead of knots constituting matter itself, the new model elevates cosmic knots as pivotal players in the genesis of matter. They are the primordial architects, the “grandparents” of matter, through their role in generating the heavy neutrinos whose decays sculpt the universe’s matter content.

Looking forward, the team acknowledges that much work remains. Refining theoretical frameworks and performing detailed numerical simulations will be essential to precisely forecast knot formation rates, decay dynamics, and the spectral features of the gravitational waves they emit. Establishing stronger connections between theoretical predictions and observational signatures will test the knot-dominated era hypothesis against empirical data. If forthcoming gravitational-wave experiments validate these predictions, it could signify a major paradigm shift in our understanding of cosmological evolution.

This union of topology, field theory, and cosmology not only unravels new paths to solving the baryon asymmetry problem but also opens innovative avenues for uncovering the nature of dark matter and the mass of neutrinos within a unified framework. The interdisciplinary reach of these discoveries stands to influence particle physics, astrophysics, and cosmology alike, propelling scientific inquiry toward a more complete narrative of the universe’s earliest moments and its progression to the complex cosmos we inhabit today.

The notion that knotted configurations of fields shaped our cosmic dawn eloquently intertwines mathematical elegance with physical reality, showcasing how revisiting historical ideas through the lens of modern science can reveal profound new insights. Its theoretical sophistication, potential observational signatures, and resolution of longstanding puzzles position this research as a milestone in the quest to decode the universe’s origins.

Subject of Research: Particle physics, cosmology, baryogenesis, and topological solitons

Article Title: Tying Knots in Particle Physics

News Publication Date: 29-Aug-2025

Web References: https://journals.aps.org/prl/abstract/10.1103/s3vd-brsn

References: Physical Review Letters, DOI: 10.1103/s3vd-brsn

Image Credits: Muneto Nitta/Hiroshima University

Keywords

Physics, Baryons, Leptons, Dark matter, Gravitational waves, Neutrinos, Solitons, Antimatter, Quantum tunneling

At the heart of this achievement lies the BASE-STEP system—an open, superconducting, transportable Penning trap designed to autonomously confine charged particles, such as protons and, in the future, antiprotons. Penning traps utilize a combination of strong magnetic and electric fields to confine charged particles in a defined region of space, enabling ultra-precise measurements of their fundamental properties. Traditionally, these systems require stringent laboratory settings with stable electromagnetic environments, but BASE-STEP’s novel design allows it to operate independently during transportation in conventional vehicles amid everyday environmental noise.

The significance of relocating these particles cannot be overstated. CERN’s Antimatter Factory produces low-energy antiprotons, essential for probing fundamental symmetries in physics with extraordinary precision. However, performing these delicate experiments near accelerators is fraught with challenges; magnetic field fluctuations from accelerator operations severely limit measurement accuracy. Thus, transporting antiprotons to specialized laboratories equipped for ultra-sensitive measurements—such as the new BASE-HHU facility in Düsseldorf—is crucial for advancing the understanding of matter-antimatter asymmetries.

Protons, the basic constituents of ordinary matter, share an almost perfect mirrored counterpart in antiprotons, which bear identical mass but opposite electric charge and magnetic moment. According to the Standard Model of particle physics, both should exhibit symmetrical properties; however, slight differences must exist to explain the observed excess of matter over antimatter in the universe. BASE seeks to identify these subtle deviations by exploiting the precision capabilities of Penning traps and advanced spectroscopic techniques.

Professor Dr. Stefan Ulmer, a leading physicist at HHU and founder of the BASE collaboration, emphasizes the challenge posed by the noisy electromagnetic environment near accelerator centers: “Achieving the sensitivity required to detect minute anomalies in the magnetic moment or charge-to-mass ratio demands an environment largely free of magnetic disturbances.” This necessity spurred the development of a mobile solution, enabling trapped particles to be relocated without loss or perturbation.

In the autumn of 2024, the team demonstrated the first-ever lossless transport of a cloud of protons from CERN’s Antimatter Factory using BASE-STEP. Operated autonomously and without external power for over four hours, the system maintained confinement integrity throughout typical road transit conditions. This milestone operation confirms that the intricate electromagnetic confinement of charged particles can survive transportation outside shielded laboratory environments—a feat previously deemed nearly unattainable.

Marcel Leonhardt, a master’s student at HHU and lead author of the pioneering study detailing these results, notes the broader implications: “The ability to safely and reliably transport particles in everyday traffic scenarios opens unprecedented opportunities for collaborative experiments across the continent. We could envision a network of laboratories sharing antimatter and exotic ions for detailed study without geographical limitations.”

The BASE-STEP system’s modular design also includes adaptability for extended journeys. Mobile power units can supply continuous operation beyond the initial autonomous four-hour window, theoretically enabling intercity or even intercontinental transport. Dr. Christian Smorra, project leader, envisions a future where laboratories across Europe, and eventually the world, can exchange rare particle samples, catalyzing an era of distributed precision science.

As promising as the proton transport results are, the ultimate goal remains the lossless relocation of antiprotons. These particles, essential for mass, charge, and magnetic moment comparison experiments, are produced only at CERN’s unique Antiproton Decelerator facility. Success in transporting these delicate antiparticles will alleviate the need for duplicative antimatter facilities and facilitate unprecedented measurement accuracies by leveraging optimal experimental environments.

Beyond antiprotons, the technology’s versatility offers a gateway to studying a plethora of exotic species including highly charged ions, molecular ions, and charged antimatter ions. Transporting these species independently of accelerator labs can fundamentally change the landscape of precision spectroscopy, quantum state preparation, and fundamental symmetry testing across physics and chemistry disciplines.

Continued refinement of autonomous, superconducting trapping and transport technologies stands to transform antimatter research into a more collaborative and globally accessible enterprise. Enabling high-precision measurements in optimized conditions far from high-energy particle accelerators circumvents magnetic interference, potentially pushing the frontier of our understanding of CPT (charge-parity-time) invariance and the underpinnings of the Standard Model itself.

The BASE collaboration has already delivered the most exacting tests of CPT symmetry with baryons, achieving relative uncertainties in the charge-to-mass ratio measurements at the astonishingly small scale of parts per trillion. This new capability to relocate particles without loss complements these achievements by expanding where such tests can be conducted, likely accelerating discovery and validation phases for fundamental physics inquiries.

In essence, the autonomous Penning-trap transport system not only solves a long-standing logistical issue in antimatter science but also unlocks a new paradigm in experimental flexibility. As the team moves toward successfully transporting antiprotons, the physics community stands on the cusp of enhanced precision measurements that may unveil the anomalies revealing the universe’s primordial matter-antimatter imbalance.

This groundbreaking work, published in the prestigious journal Nature, was primarily supported by the European Research Council and represents a milestone achievement for the BASE international collaboration—a consortium including institutes from Germany, Switzerland, the United Kingdom, and Japan. It highlights the synergetic blend of cutting-edge physics, engineering ingenuity, and collaborative scientific vision now driving antimatter research into the future.

Subject of Research: Transport and confinement of protons and antiprotons using autonomous Penning traps for high-precision antimatter research

Article Title: Proton Transport from the Antimatter Factory of CERN

News Publication Date: 14-May-2025

Web References:
https://www.nature.com/articles/s41586-025-08926-y
https://home.cern/science/experiments/base

References:
M. Leonhardt, D. Schweitzer, F. Abbass, K. K. Anjum, B. Arndt, S. Erlewein, S. Endo, P. Geissler, T. Imamura, J. I. Jäger, B. M. Latacz, P. Micke, F. Voelksen, H. Yildiz, K. Blaum, J. A. Devlin, Y. Matsuda, C. Ospelkaus, W. Quint, A. Soter, J. Walz, Y. Yamazaki, S. Ulmer, and C. Smorra. Proton Transport from the Antimatter Factory of CERN. Nature (2025). DOI: 10.1038/s41586-025-08926-y

Image Credits: BASE/Julia Jäger

Keywords

Protons, Antimatter, Penning trap, Particle transport, CPT invariance, Antiproton Decelerator, High-precision spectroscopy, BASE collaboration, Superconducting trap, Fundamental symmetries