Kavli Affiliate: Satoshi Shirai
| First 5 Authors: Akifumi Chitose, Masahiro Ibe, Yuhei Nakayama, Satoshi Shirai, Keiichi Watanabe
| Summary:
Metastable cosmic strings appear in models of new physics with a two-step
symmetry breaking $Gto Hto 1$, where $pi_1(H)neq 0$ and $pi_1(G)=0$. They
decay via the monopole-antimonopole pair creation inside. Conventionally, the
breaking rate has been estimated by an infinitely thin string approximation,
which requires a large hierarchy between the symmetry breaking scales. In this
paper, we reexamine it by taking into account the finite sizes of both the
cosmic string and the monopole. We obtain a robust lower limit on the tunneling
factor $e^{-S_B}$ even for regimes the conventional estimate is unreliable. In
particular, it is relevant to the cosmic string interpretation of the
gravitational wave signals recently reported by pulsar timing array
experiments.
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