LRS Bianchi Type-II Massive String Cosmological Models in General Relativity

The present study deals with locally rotationally symmetric (LRS) Bianchi type II cosmological models representing massive string. The energy-momentum tensor for such string as formulated by Letelier (1983) is used to construct massive string cosmological models for which we assume that the expansion ($\theta$) in the models is proportional to the shear ($\sigma$). This condition leads to $A=B^m$, where A and B are the metric coefficients and m is constant. We have derived two types of models depending on different values of m i.e. for $m\mathrm{\ne }\sqrt{2}$ and $m=\sqrt{2}$ respectively. For suitable choice of constant m (i.e. for $m=1\mathrm{/}2$), it is observed that in early stage of the evolution of the universe, the universe is dominated by strings in both cases. Our models are in accelerating phase which is consistent to the recent observations of type Is supernovae. Some physical and geometric behaviour of the models are also discussed.