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The hidden mechanics of abrupt transitions: Superconducting networks show how tiny changes trigger system collapse

The hidden mechanics of abrupt transitions: how tiny changes trigger a global collapse
Mixed-order transitions in interdependent superconducting networks. Credit: Nature Communications (2025). DOI: 10.1038/s41467-025-61127-z

Why do some changes in nature unfold gradually, while others occur in the blink of an eye? Rust forming on metal is a slow, steady process that takes days or even weeks to become visible. By contrast, a power grid can collapse in mere seconds. What accounts for this difference?

A research team at Bar-Ilan University has uncovered a surprising mechanism behind these abrupt transitions, a hidden spontaneous sequence of micro-scale events that gradually destabilize a system until it snaps. Their discovery sheds new light on how behave near critical tipping points and offers a new way to anticipate and perhaps even prevent catastrophic failure.

In their study just published in , the team led by Professors Shlomo Havlin and Aviad Frydman—alongside BIU researchers Ira Volotsenko, Yuval Sallem, and Nahala Yadid, and postdoctoral collaborators Bnaya Gross (Northeastern University) and Ivan Bonamassa (CEU Vienna)—investigated a novel engineered experimental system: interdependent superconducting networks.

These networks consist of two overlapping grids of superconducting wires, materials that conduct electricity without resistance when cooled below a . While each grid can function independently, the most remarkable behavior emerges when they interact through heat exchange.

Here's the twist: when this system approaches a "critical" point, for example, by increasing the , it doesn't transition smoothly from a superconducting state to a resistive one. Instead, the system lingers, for hundreds of seconds, in a long-lived intermediate phase. Then, without further prompting, it abruptly transitions into the new state. What causes this mysterious pause?

The answer lies in a spontaneous cascading process. When a single segment of one network switches its phase from a superconducting to a resistive state, it releases heat. This heat affects a random segment in the second network, triggering another change. One change sparks another, like dominoes falling not in a straight line, but scattered across space, each toppling the next through indirect connections.

A video illustrating the microscopic random cascading process that leads to the long-lived macroscopic plateau as illustrated in Figs.~4 and 5. Credit: Nature Communications (2025). DOI: 10.1038/s41467-025-61127-z

This , while slow and localized at first, sets the stage for a sudden, global collapse, akin to the final moment in a game of Jenga, when the structure has quietly weakened with each block removed, until removing one final block brings it all crashing down.

At the heart of this behavior is a concept known as the branching factor—a term that gained prominence during the COVID-19 pandemic. It represents the average number of new changes triggered by each event. When the branching factor is less than one, the cascade quickly dies out. If it exceeds one, the process accelerates uncontrollably.

But when the branching factor is exactly one, the system reaches a , delicately balanced between stability and a cascading collapse. A similar tipping-point dynamic appears in the spread of epidemics: when each infected person passes the virus to exactly one other, the outbreak teeters on the edge.

Below this threshold, the outbreak dies out; above it, the epidemic spreads rapidly. The Bar-Ilan University team's real-time measurements of this branching factor in superconducting systems provide a rare glimpse into this critical regime and, more importantly, offer a potential early warning signal for when complex systems are about to collapse.

This discovery is significant because it reveals how tiny, random changes, initially harmless, can trigger sudden spontaneously massive transformations. Remarkably, it also gives us a powerful tool: by monitoring how much each small change spreads (the "branching factor"), we might predict when a system, whether it's a high-tech material, an electrical grid, or even an ecosystem, is nearing a critical breakdown.

So next time something suddenly fails, whether it's a blackout or a system crash, remember: the seeds of collapse may have been sown much earlier, one quiet change at a time.

More information: Bnaya Gross et al, The random cascading origin of abrupt transitions in interdependent systems, Nature Communications (2025).

Journal information: Nature Communications

Provided by Bar-Ilan University

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