Kantowski-Sachs String Cosmologies

Abstract

We present new exact solutions of the low-energy-effective-action string equations with both dilaton $\varphi$ and axion $H$ fields non-zero. The background universe is of Kantowski-Sachs type. We consider the possibility of a pseudoscalar axion field $h$ ($H=e^{\varphi }(dh{)}^{\ast }$) that can be either time or space dependent. The case of time-dependent $h$ reduces to that of a stiff perfect-fluid cosmology. For space-dependent $h$ there is just one non-zero time-space-space component of the axion field $H$, and this corresponds to a distinguished direction in space which prevents the models from isotropising. Also, in the latter case, both the axion field $H$ and its tensor potential $B$ ($H=dB$) are dependent on time and space yet the energy-momentum tensor remains time-dependent as required by the homogeneity of the cosmological model.

23 pages, REVTEX, 6 figures available on request

References in corpus (1)

• Spatially Homogeneous String Cosmologies

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