Vacuum polarisation of Dirac fermions in the cosmological de Sitter-global monopole spacetime

Abstract

We study the vacuum polarisation effects of the Dirac fermionic field induced by a pointlike global monopole located in the cosmological de Sitter spacetime. First we derive the four orthonormal Dirac modes in this background in a closed form. Quantising the field using these modes, we then compute the fermionic condensate, $⟨0|\overline{\Psi }\Psi |0⟩$, as well as the vacuum expectation value of the energy-momentum tensor for a massive Dirac field, regularised in a particular way. We have used the Abel-Plana summation formula in order to extract the global monopole contribution to these quantities and have investigated their variations numerically with respect to relevant parameters.

v1; 30pp,6 figs, references added, the newly added texts and equations with proper presentations, Accepted for publication in Physical Review D

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