Interactions of non-Abelian global strings

Non-Abelian global strings are expected to form during the chiral phase transition. They have orientational zero modes in the internal space, associated with the vector-like symmetry SU_(N)L+R$\mathit{SU}{(N)}_{\mathrm{L}+\mathrm{R}}$ broken in the presence of strings. The interaction among two parallel non-Abelian global strings is derived for general relative orientational zero modes, giving a non-Abelian generalization of the Magnus force. It is shown that when the orientations of the strings are the same, the repulsive force reaches the maximum, whereas when the relative orientation becomes the maximum, no force exists between the strings. For the Abelian case we find a finite volume correction to the known result. The marginal instability of the previously known Abelian η^′${\eta }^{\prime }$ strings is discussed.     

Self-gravitating general-relativistic cosmic strings

We examine the coupled Einstem-Euler-Lagrange equations for nonstationary cosmic strings. Self-consistent solutions to all the equations are found under the assumption that the energy-momentum tensor is of the formT _t ^t =T _z ^z while all other components vanish. It is shown that the strings are necessarily static in this case and that the scalar field potential must be of the usual quartic form with the coupling constants satisfying e²=8.     

Stable charged cosmic strings

We study the quantum stabilization of a cosmic string by a heavy fermion doublet in a reduced version of the standard model. We show that charged strings, obtained by populating fermionic bound state levels, become stable if the electroweak bosons are coupled to a fermion that is less than twice as heavy as the top quark. This result suggests that extraordinarily large fermion masses or unrealistic couplings are not required to bind a cosmic string in the standard model. Numerically we find the most favorable string profile to be a simple trough in the Higgs vacuum expectation value of radius ≈10(-18) m. The vacuum remains stable in our model, because neutral strings are not energetically favored.     

Skyrme-Einstein closed cosmic chiral strings

Within the theory of general relativity, the configuration of a closed string (vortex) characterized by a topological charge of the degree type is described for the Skyrme-Einstein SU (2) chiral model. In the approximation of a large vortex-closure radius (a), a solution to equations of motion is obtained, along with estimates for the vortex energy and radius.     

Notes on superconducting cosmic strings

Several problems in string electrodynamics are discussed. Electric currents induced in strings oscillating in stationary electric and magnetic fields are calculated. In some cases the currents grow linearly with time. The rate of pair production in the electromagnetic field of strings is estimated.