The University of Padova and INFN successfully reproduced complicated particle scattering in a two-dimensional quantum system, challenging semi-classical expectations. The 2026 Nature Communications paper reveals how high-energy collisions might cause the violent decay of a metastable “false vacuum,” impacting the view of astronomy and the early universe.
Moving Beyond the First Dimension
Real-time scattering simulations have been traditionally limited to one spatial dimension (1D). Although 1D models are simpler to compute, they contain the necessary “physics content” to explain complicated 3D phenomena like limits, resonance, and topological order. Extending simulations to 2D is crucial for accurately expressing realistic theories, according to authorities.
The team composed of Luka Pavešić, Marco Di Liberto, and Simone Montangero, used Tree Tensor Networks (TTN), to overcome the “methodological nature” of 1D restrictions. In contrast to MPS, TTNs use a binary tree structure to reduce the “distance” between physical sites from linear to exponential, enabling accurate simulations on a 24 × 24 lattice with 576 spins.
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The Three Faces of Distribution
The researchers produced wave packets of magnons, elementary spin waves, and impacted them at different strengths of a diagonal magnetic field (g). Researchers found three dynamical phases in these collisions:
- Elastic Scattering: At small fields (g/J≲1.0), particles bounced off each other predictably, with total magnetization remaining approximately conserved.
- Intermediate Resonance: At moderate fields (g/J∼1.5), the collision produced composite bound states—heavier intermediate particles—which then decayed back into pairs of magnons.
- Strongly Inelastic Regime: At large fields (g/J∼2.0), the interaction became highly complex, resulting in a three-particle process where a heavy central excitation was created alongside two outward-propagating magnons.
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The False Vacuum Decay
The researchers made a significant discovery by creating a “false vacuum” by breaking the system’s symmetry with a horizontal field (h), which is not the lowest-energy configuration. In this stage, the system is like a ball in a shallow dip on a hillside: stable initially, but needs a push to fall to its true bottom.
The group discovered that two particles can create a bubble of the “true vacuum” when they collide with sufficient energy in this false vacuum. After reaching a critical size, this bubble self-sustainingly grows to include the entire system. Based on ballistic expansion, the genuine vacuum consumes the illusory vacuum at a steady speed.
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Challenging Classical Expectations
This discovery is important as it challenges semi-classical assumptions in quantum field theory (QFT). Previous estimates indicated that the chance of two particles causing decay should be “exponentially suppressed” even at infinite energies. Researchers think stable coherent processes at larger transverse fields explain their conclusion, where classical approximations fail.
The entry for decay at low field strengths exceeds the energy needed to pass the potential barrier, indicating complicated quantum interactions are necessary for the system to tunnel past the barrier.
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The Prospects for Quantum Spectroscopes
Classical simulation of events using NVIDIA H100 GPUs and the “Quantum Tea” toolkit is a significant advancement in computational physics. According to the researchers, classical techniques cannot accurately capture the long-term dynamics of a highly entangled, coherent bubble expansion.
This highlights need for induced false vacuum decay for future quantum simulators. The study of composite excitations is crucial for understanding high-temperature superconductors and “spectroscopic sensors” in condensed matter physics, beyond astronomy. Scientists can discover matter’s origin and death, previously veiled by global constraints, by scattering energy locally.
