Casimir Energy for Finite-Core Cosmic Strings

We consider the Casimir effect of two parallel infinitely-long cosmic strings which interact via massless real scalar field. We test two models of the finite width: so-called ‘‘flower-pot’’ model and ‘‘ballpoint-pen’’ model. The energy of the Casimir attraction is computed in analytic form. The ‘‘flower-pot’’ model predicts much stronger attraction, in particular at a close string contact. Both models reproduce proper limit at ultralarge interstring distances.