cosmic strings

cosmic strings
Name	Cosmic strings
Caption	Artist's impression of one-dimensional topological defects in a cosmological context
Type	Hypothetical topological defect
Proposed	1970s
Proponents	Tom Kibble, Alexander Vilenkin, Kenneth Wilson
Significance	Possible relics from symmetry-breaking phase transitions in the early Universe

cosmic strings Cosmic strings are hypothetical one-dimensional topological defects predicted by some Grand Unified Theorys and field-theory models of the early Big Bang. They were first proposed during studies of spontaneous symmetry breaking in the 1970s by Tom Kibble and others, and later analyzed in contexts involving Inflation (cosmology), Supersymmetry, and String theory. Interest in the topic spans work by theorists associated with CERN, Princeton University, Harvard University, and Cambridge University.

Overview

Cosmic strings are line-like concentrations of energy that could form when a symmetry-breaking phase transition leaves a degenerate vacuum manifold with nontrivial first homotopy group; early analyses connected them to phase transitions in Grand Unified Theory models and to mechanisms studied at Fermi National Accelerator Laboratory and SLAC National Accelerator Laboratory. The possibility of cosmological defects motivated cross-disciplinary studies involving researchers at Stanford University, Caltech, University of Oxford, Massachusetts Institute of Technology, and institutes such as the Perimeter Institute and Kavli Institute for Theoretical Physics. Their study has intersected with work on Monopoles, Domain walls, and Textures investigated at Los Alamos National Laboratory and in collaboration with groups at NASA.

Theoretical Origins and Models

The earliest derivations used field-theoretic models like the Abelian-Higgs model and non-Abelian gauge theories explored by Kenneth Wilson and Alexander Polyakov, applying methods developed in Statistical mechanics and lattice gauge simulations performed at CERN and Brookhaven National Laboratory. Kibble’s mechanism linked defect formation to causally disconnected regions during symmetry breaking, a concept also central to studies at Harvard-Smithsonian Center for Astrophysics and Max Planck Institute for Physics. Later work embedded line defects into Superstring theory scenarios, yielding "cosmic superstrings" studied by researchers at University of Cambridge and Rutgers University, and related to dualities developed by Edward Witten and Joseph Polchinski. Models include Nambu–Goto strings, studied using techniques from Richard Feynman-inspired path integrals, and field-theory strings whose microphysics involves Higgs and gauge fields analyzed in the tradition of Yoichiro Nambu.

Physical Properties and Dynamics

Strings are characterized by a tension μ and relativistic dynamics derived from the Nambu–Goto action, with parameters often expressed via the dimensionless combination Gμ where G is Newton’s constant; these quantities have been constrained using observations from European Space Agency missions and analyses by groups at Space Telescope Science Institute. Network evolution features intercommutation, loop formation, and gravitational radiation emission, topics pursued by simulators at Princeton Plasma Physics Laboratory and computational efforts at Argonne National Laboratory. Small-scale structure like cusps and kinks, predicted in analytic work by T. Vachaspati and A. Vilenkin, affects gravitational-wave spectra targeted by collaborations such as LIGO Scientific Collaboration, VIRGO (gravitational-wave detector), KAGRA, and pulsar timing arrays including the North American Nanohertz Observatory for Gravitational Waves.

Cosmological Implications

If present, strings could seed density perturbations, influence anisotropies measured by the Wilkinson Microwave Anisotropy Probe and Planck teams, and leave signatures in the Cosmic Microwave Background similar to those sought by researchers at Space Science Institute and Jet Propulsion Laboratory. Early suggestions that strings could account for large-scale structure involved comparisons to surveys undertaken by the Sloan Digital Sky Survey and Two Micron All-Sky Survey teams, though subsequent constraints shifted focus to subdominant roles. Strings also play a role in baryogenesis scenarios considered by theorists at Yale University and Columbia University and in models linking dark matter candidates explored at Fermilab and in collaborations at Brookhaven National Laboratory.

Observational Searches and Constraints

Search strategies include looking for gravitational lensing events akin to those catalogued by the Hubble Space Telescope and deep-field programs at the European Southern Observatory, along with searches for bursts of gravitational waves by LIGO Scientific Collaboration, VIRGO, and pulsar timing consortia such as European Pulsar Timing Array and International Pulsar Timing Array. Constraints on Gμ have been reported by teams at Planck Collaboration, WMAP Science Team, NANOGrav Collaboration, and analyses associated with Australian National University pulsar groups. High-energy signatures, like particle emission from cusps, motivated gamma-ray and cosmic-ray searches by Fermi Gamma-ray Space Telescope, Pierre Auger Observatory, and IceCube Neutrino Observatory collaborations. Null results from many observational campaigns have led groups at University of Chicago and Institute for Advanced Study to tighten bounds on viable models.

Related Phenomena and Analogues

Analogues of cosmic strings appear in condensed-matter systems such as vortex lines in superfluid helium studied at Royal Society-funded laboratories, flux tubes in type-II superconductors investigated by teams at Bell Labs and IBM Research, and defect dynamics in liquid crystals researched at University of Pennsylvania and University of Cambridge. Mathematical parallels connect to solitons in integrable systems explored by Martin Kruskal and to kinks studied in the context of Soliton (physics) theory at institutions like University of Tokyo. Experimental analogue gravity programs at University of Nottingham and Technion – Israel Institute of Technology emulate aspects of string-induced metrics, while interdisciplinary workshops at Perimeter Institute and ICTP have fostered cross-pollination between cosmology, condensed matter, and high-energy theory.

Category:Topological defects