Gravitational waves in a stringlike fluid cosmology
  The coupling of a stringlike fluid with ordinary matter and gravity may lead to a closed Universe with the dynamic of an open one. This can provide an alternative solution for the age and horizon problems. A study of density perturbations of the stringlike fluid indicates the existence of instabilities in the small wavelength limit when it is employed a hydrodynamic approach. Here, we extend this study to gravitational waves, where the hydrodynamical approach plays a less important role, and we argue that traces of the existence of this fluid must be present in the anisotropies of the cosmic background radiation. 
J.C. Fabris (1) and S.V.B. Goncalves (2) ((1) Departamento de Fisica,   Universidade Federal do Espirito Santo (2) Instituto...