Metastable cosmic strings are broken at the start

Journal article

We show that metastable cosmic strings break at early times, either via finite-temperature effects or by attaching to pre-existing monopoles during network percolation. The resulting segments can be initially super-horizon in size and thus persist for a significant amount of time. If the strings do not re-percolate, the network’s eventual destruction is typically due to this early-time breaking rather than late-time quantum tunnelling. Survival of strings to epochs probed by NANOGrav requires m² _M/µ ≳ 10³ , where m_M and µ are the monopole mass and the string tension respectively, over an order of magnitude larger than previous estimates. We also revisit quantum-tunnelling induced breaking. Results from numerical simulations suggest that this occurs mainly at rare high-tension points on the strings, yielding a rate much larger than is usually assumed. We briefly discuss the related scenario of flux tubes in a dark QCD-like hidden sector with dark-quark masses above the confinement scale.

Authors: Tranchedone, L; Carragher, E; Hardy, E; Koscelanská van IJcken, N

• Publication status: Accepted
• Peer review status: Peer reviewed
• Publisher: Springer
• Journal: Journal of High Energy Physics
• Acceptance date: 2026-06-16
• EISSN: 1029-8479
• ISSN: 1126-6708
• Language: English