Quantum aspects of self-interacting fields around cosmic strings

The authors study the quantum effect of self-interacting fields in the classical background of conical space, i.e. around a cosmic string with infinitesimal width. The renormalized value of $\langle\phi^2\rangle$ and energy-momentum tensor in the presence of cosmic strings are calculated in the self-interacting scalar field theory. The amount of condensation is also estimated in the case of the Dirac Lagrangian with the four-fermion interaction. The physical implications of the above analyses are discussed.