We present an analytic model specifically designed to address the long standing issue of small scale structure on cosmic string networks. The model is derived from the microscopic string equations, together with a few motivated assumptions. The resulting form of the correlation between two points on a string is exploited to study smoothing by gravitational radiation, loop formation and lensing by cosmic strings. In addition, the properties of the small loop population and the possibility of detecting gravitational waves generated by their lowest harmonics are investigated. Whenever possible, we compare the predictions of the model to the most recent numerical simulations of cosmic string networks.
We study massless cosmic strings which are one-dimensional objects moving with the speed of light. Perturbations of velocities of test bodies and anisotropy of cosmic microwave background generated by massless cosmic strings are analysed. These phenomena are analogous to the string wake effect and the Kaiser-Stebbins effect for standard (massive) cosmic strings. There are two regimes depending on the energy $E$ of a massless string per unit length. At low energies, $EG/c^4\ll 1$, massless and massive strings act similarly. At high energies, $EG/c^4 \sim 1$, massless string effects are quite di…
Circular massless cosmic strings which move with the speed of light in the de Sitter universe are described. Construction of the background geometry is based on parabolic isometries of the de Sitter spacetime. Microscopic circular cosmic strings may appear at the Planck epoch and then grow up to the Hubble size. We analyze: images of the strings, influence of strings on trajectories of matter, formation of overdensities, and shifts of energies of photons. These effects allow one to discriminate massless strings from their massive cousins. The present work extends our results on straight massle…
In this work the gravitational lensing in the strong field limit around the Schwarzschild black hole pierced by a cosmic string is studied. We find that the deflection angle and the time delay of the relativistic images depend on the tension of cosmic string. It is interesting that the deflection angle is greater when the tension of cosmic string is stronger. The time delay between two images is more obvious in the case of weaker tension.
In this article, the thermodynamics of regular black holes with a cosmic string passing through it is studied. We will observe that the string has no effect on the temperature as well as the relation between entropy S and horizon area A.
Multiple gauge theories predict the presence of cosmic strings with different mass densities $Gμ/c^2$. We derive an equation governing the perturbations of a rotating black hole pierced by a straight, infinitely long cosmic string along its axis of rotation and calculate the quasinormal-mode frequencies of such a black hole. We then carry out parameter estimation on the first detected gravitational-wave event, GW150914, by hypothesizing that there is a string piercing through the remnant, yielding a constraint of $Gμ/c^2 <3.8\times 10^{-3}$ at the 90\% confidence interval with a comparable Bay…
The interpretation of so-called cosmic string in black hole spacetimes has settled down to an unsatisfactory state. In this article we try to provide a different model for these cosmic strings by explicit construction of these spacetimes from the Bonnor rocket solution. It is shown that the correct stress-energy tensor is that of null dust with a rather strange energy density --- first derivative of Dirac delta distribution. We will discuss the Schwarzschild solution and the C--metric. In the latter case we will show that there is a momentum flux through the cosmic string, causing the accelera…
We report the effect of the cosmological constant and the internal energy density of a cosmic string on the deflection angle of light in the spacetime of a rotating cosmic string with internal structure. We first revisit the deflection angle by a rotating cosmic string and then provide a generalization using the geodesic equations and the Gauss-Bonnet Theorem. We show there is an agreement between the two methods when employing higher order terms of the linear mass density of the cosmic string. By modifying the integration domain for the global conical topology, we resolve the inconsistency be…
In this work we deal with the spacetime shaped by a straight cosmic string, emerging from local gauge theories, in the braneworld gravity context. We search for physical consequences of string features due to the modified gravitational scenario encoded in the projected gravitational equations. It is shown that cosmic strings in braneworld gravity may present significant differences when compared to the general relativity predictions since its linear density is modified and the deficit angle produced by the cosmic string is attenuated. Furthermore, the existence of cosmic strings in that scenar…
We examine the effect of a wiggly cosmic string for both massless and massive particle propagation along the string axis. We show that the wave equation that governs the propagation of a scalar field in the neighborhood of a wiggly string is formally equivalent to the quantum wave equation describing the hydrogen atom in two dimensions. We further show that the wiggly string spacetime behaves as a gravitational waveguide in which the quantized wave modes propagate with frequencies that depend on the mass, string energy density, and string tension. We propose an analogy with an optical fiber, d…
Cosmic strings produce charged particles which, by emitting electromagnetic radiation, partially ionize neutral hydrogen during the dark ages. Corrections to the ionization fraction of neutral hydrogen induced by cosmic strings could lead to new observational effects and/or new constraints on the string tension around $Gμ\sim 10^{-16} - 10^{-22}$ for values of the primordial magnetic field in the range $B_0 \sim 10^{-11}-10^{-9}$ Gauss.
