
Gravitational waves produced by cosmic strings, including those with magnetic monopoles or currents.Cosmic strings are hypothetical one-dimensional defects in spacetime, predicted by many grand unified theories. They are extremely thin — thinner than a proton — but can stretch across the entire universe, carrying enormous energy densities. When two cosmic strings intersect or oscillate, they can produce cusps and kinks that emit intense bursts of gravitational waves. Unlike the gravitational waves from black hole mergers, which are short-lived chirps, cosmic string signals would be a stochastic background of bursts, potentially detectable by pulsar timing arrays or space-based interferometers. Some strings may also carry electric currents or magnetic monopoles, which would alter their dynamics and gravitational-wave emission.
Cosmic strings were first proposed by Tom Kibble in 1976 as a consequence of symmetry breaking in the early universe. Their gravitational-wave signatures were studied extensively in the 1980s and 1990s, and they remain a key target for gravitational-wave observatories.
A cosmic string is a concentration of energy that curves spacetime around it. When a string moves, it can emit gravitational radiation, especially at points where it moves at nearly the speed of light (cusps) or where it has sharp bends (kinks). If a string carries a current, it can also emit electromagnetic radiation, and if it has monopoles attached, these can slide along the string and collide, producing additional gravitational-wave bursts. The frequency and amplitude of these waves depend on the string tension and the presence of currents, making them a unique probe of high-energy physics.
Gravitational-wave detectors like LIGO, Virgo, and pulsar timing arrays search for cosmic string signals to test grand unified theories and probe physics at energy scales far beyond particle accelerators.
If cosmic strings exist, they could have seeded the formation of galaxies by creating density fluctuations in the early universe, acting as the 'seeds' around which matter clumped.
| μ | variable | mass per unit length of cosmic string — linear mass density kilogram per metre |
| G | constant | Newton's constant of universal gravitation — gravitational constant = 6.67430e-11 cubic metre per kilogram per second squared |
| m_Pl | constant | Planck mass, the fundamental mass scale in quantum gravity — planck mass = 2.176434e-8 kilogram |
| h_0 | variable | gravitational wave strain amplitude — strain |
| ε | variable | ellipticity — ellipticity |
| I_zz | variable | moment of inertia about rotation axis — moment of inertia kilogram metre squared |
| f_GW | variable | gravitational wave frequency — frequency hertz |
| d | variable | distance to source — distance metre |
| G | constant | Newton's constant of universal gravitation — gravitational constant = 6.67430e-11 cubic metre per kilogram per second squared |
| c | constant | Speed of light in vacuum — speed of light = 299792458 metre per second |








