Cosmic Strings

Abstract

Cosmic strings, a hot subject in the 1980's and early 1990's, lost its appeal when it was found that it leads to inconsistencies in the power spectrum of the measured cosmic microwave background temperature anisotropies. However, topological defects in general, and cosmic strings in particular, are deeply rooted in the framework of grand unified theories. Indeed, it was shown that cosmic strings are expected to be generically formed within supersymmetric grand unified theories. This theoretical support gave a new boost to the field of cosmic strings, a boost which has been recently enhanced when it was shown that cosmic superstrings (fundamental or one-dimensional Dirichlet branes) can play the role of cosmic strings, in the framework of braneworld cosmologies. To build a cosmological scenario we employ high energy physics; inflation and cosmic strings then naturally appear. Confronting the predictions of the cosmological scenario against current astrophysical/cosmological data we impose constraints on its free parameters, obtaining information about the high energy physics we employed. This is a beautiful example of the rich and fruitful interplay between cosmology and high energy physics.Comment: 42 pages, 7 figures, Chapter for the book "Quantum Simulations via Analogues: From Phase Transitions to Black Holes", to appear in Springer lecture notes in physics (LNP); a few modifications and new references to match published versio

Gravitational wave bursts from cosmic string cusps and pseudocusps

“…(2.1) with respect to the metric yields the string energy-momentum tensor for any position vector x λ 16) where the dependences of X µ , X µ andẊ µ in σ and t have been hidden and δ (4) is the four dimensional Dirac delta function. In the Fourier domain, for any point k λ in momentum space, one obtains 17) where L is the period in σ ± and Σ is the compact string worldsheet (…”

“…Therefore, we have chosen safer, more stringent limits to ensure our automated treatment is considering the correct (stable, high end) frequencies for the study of T , reducing the window on each end by two points on a logarithmic scale, from ω ∈ [10, 10 4 ] to ω ∈ [16, 6400] Hz. 4 This procedure leaves us with a 2.6-order-of-magnitude investigation window, that is, for the frequency f = ω /2π in Eq. (2.28), an interval f ∈ [2.52, 1000] Hz, where we are considering the waveform slope dependance for different highly relativistic points.…”

“…Applying Grand Unified Theories (GUTs) in the context of the early Universe, one concludes that as the Universe expands and its temperature drops, it undergoes a series of phase transitions followed by spontaneously broken symmetries, which may leave behind topological defects as false vacuum remnants [1][2][3][4][5]. Cosmic strings are one-dimensional such topological defects, generically formed after a period of hybrid inflation [6]; they can lead to a variety of observational consequences.…”

Super-horizon cosmic string correlations

“…Cosmic strings [1,2,3] are hypothetical string-like objects, which are stable and extremely massive and whose existence is predicted by many field theory [4] and string theory models [5] of particle physics. If they exist in nature, they would have generally been formed in the early universe in symmetry breaking phase transitions [1], or in brane collisions [6] in brane world models.…”

Production of Topological Defects at the End of Inflation

“…Cosmic strings [19] are analogous to flux tubes in type-II superconductors, or to vortex filaments in superfluid helium. Topologically stable strings do not have ends; they either form closed loops or they extend to infinity.…”