Detecting Cosmic Strings with Lensed Fast Radio Bursts

Understand

Correlated red noise recently reported from pulsar timing observations may be an indication of stochastic gravitational waves emitted by cosmic strings that formed during a primordial phase transition near the Grand Unification energy scale.

• Unfortunately, known probes of cosmic strings, namely the Cosmic Microwave Background anisotropies and string lensing of extragalactic galaxies, are not sensitive enough for low string tensions of $G\mu = 10^{-10}-10^{-7}$ that are needed to explain this putative signal.
• We show that strong gravitational lensing of Fast Radio Bursts (FRBs) by cosmic strings is a potentially unambiguous avenue to probe that range of string tension values.
• The image pair of string lensing are expected to have identical magnification factor and parity, and have a typical time delay of $\sim 10^2\,\,(G\,\mu/10^{-8})^2$ seconds.