paper

On the quadratic action of the Hawking-Turok instanton

arXiv:gr-qc/9804056 · doi:10.1103/PhysRevD.58.063505

Abstract

Positive definiteness of the quadratic part of the action of the Hawking-Turok instanton is investigated. The Euclidean quadratic action for scalar perturbations is expressed in terms of a single gauge invariant quantity . The mode functions satisfy a Schrödinger type equation with a potential . It is shown that the potential tends to a positive constant at the regular end of the instanton. The detailed shape of depends on the initial data of the instanton, on parameters of the background scalar field potential and on a positive integer, , labeling different spherical harmonics. For certain well behaved scalar field potentials it is proven analytically that for quadratic action is non-negative. For the lowest (homogeneous) harmonic numerical solution of the Schrödinger equation for different scalar field potentials and different initial data show that in some cases the potential is negative in the intermediate region. We investigated the monotonously growing potentials and a potential with a false vacuum. For the monotonous potentials no negative modes are found about the Hawking-Turok instanton. For a potential with the false vacuum the HT instanton is shown to have a negative mode for certain initial data.

8 pages, REVTeX, 4 eps figures (included); statement concerning the CD solution is corrected and few other minor changes are made

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