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We present a detailed analysis of {it excited} cosmic string solutions which possess superconducting currents. These currents can be excited inside the string core, and - if the condensate is large enough - can lead to the excitations of the Higgs field. Next to the case with global unbroken symmetry, we discuss also the effects of the gauging of this symmetry and show that excited condensates persist when coupled to an electromagnetic field. The space-time of such strings is also constructed by solving the Einstein equations numerically and we show how the local scalar curvature is modified by the excitation. We consider the relevance of our results on the cosmic string network evolution as well as observations of primordial gravitational waves and cosmic rays.
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We present an analytic study of cosmic superconducting chiral string collisions in Minkowski space, applying the kinematic constraints that arise from the relevant generalization of the Nambu-Goto action. In particular, we revisit the solution for chiral superconducting cosmic strings and demonstrate that Y junction production for such strings is possible. We consider the collision of chiral current-carrying straight strings and obtain the region in angle-velocity space that allows the production of string junctions. This study contributes to the understanding of the complex evolution of chiral superconducting string networks.
Superconducting cosmic strings emit electromagnetic waves between the times of recombination and reionization. Hence, they have an effect on the global 21cm signal. We compute the resulting absorption features, focusing on strings with critical current, study their dependence on the string tension $mu$, and compare with observational results. For string tensions in the range of $G mu = 10^{-10}$, where $G$ is Newtons gravitational constant, there is an interesting amplification of the two characteristic absorption features, one during the cosmic dawn, $z lesssim 30$, and the other during the cosmic dark age, $z sim 80$, the former being comparable in amplitude to what was observed by the EDGES experiment.
Cosmic strings are generically predicted in many extensions of the Standard Model of particle physics. We propose a new avenue for detecting cosmic strings through their effect on the filamentary structure in the cosmic web. Using cosmological simulations of the density wake from a cosmic string, we examine a variety of filament structure probes. We show that the largest effect of the cosmic string is an overdensity in the filament distribution around the string wake. The signal from the overdensity is stronger at higher redshift, and more robust with a wider field. We analyze the spatial distribution of filaments from a publicly available catalog of filaments built from SDSS galaxies. With existing data, we find no evidence for the presence of a cosmic string wake with string tension parameter $Gmu$ above $5times 10^{-6}$. However, we project WFIRST will be able to detect a signal from such a wake at the $99%$ confidence level at redshift $z=2$, with significantly higher confidence and the possibility of probing lower tensions ($Gmu sim 10^{-6}$), at $z=10$. The sensitivity of this method is not competitive with constraints derived from the CMB. However, it provides an independent discovery channel at low redshift, which could be a smoking-gun in scenarios where the CMB bound can be weakened.
We first examine the microstructure of a cosmic string endowed with two simple Abelian currents. This microstructure depends on two state parameters. We then provide the macroscopic description of such a string and show that it depends on an additional Lorentz-invariant state parameter that relates the two currents. We find that in most of the parameter space, the two-current string is essentially equivalent to the single current-carrying string, i.e., only one field condenses onto the defect. In the regions where two currents are present, we find that as far as stability is concerned, one can approximate the dynamics with good accuracy using an analytic model based on either a logarithmic (on the electric side, i.e., for timelike currents) or a rational (on the magnetic side, i.e., for spacelike currents) worldsheet Lagrangian.
We investigate the effects of a brane and magnetic-flux-carrying cosmic string on the vacuum expectation value (VEV) of the current density for a charged fermionic field in the background geometry of 4+1 dimensional anti-de Sitter (AdS) spacetime. The brane is parallel to the AdS boundary and the cosmic string is orthogonal to the brane. Two types of boundary conditions are considered on the brane that include the MIT bag boundary condition and the boundary conditions in Z2-symmetric braneworld models. The brane divides the space into two regions with different properties of the vacuum state. The only nonzero component of the current density is along the azimuthal direction and in both the regions the corresponding VEV is decomposed into the brane-free and brane-induced contributions. The latter vanishes on the string and near the string the total current is dominated by the brane-free part. At large distances from the string and in the region between the brane and AdS horizon the decay of the brane-induced current density, as a function of the proper distance, is power-law for both massless and massive fields. For a massive field this behavior is essentially different from that in the Minkowski bulk. In the region between the brane and AdS boundary the large-distance decay of the current density is exponential. Depending on the boundary condition on the brane, the brane-induced contribution is dominant or subdominant in the total current density at large distances from the string. By using the results for fields realizing two inequivalent irreducible representations of the Clifford algebra, the vacuum current density is investigated in C- and P-symmetric fermionic models. Applications are given for a cosmic string in the Randall-Sundrum-type braneworld model with a single brane.
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