General Relativity and Gravitation

, Volume 27, Issue 2, pp 171–191 | Cite as

Constraints on inflationary solutions in the presence of shear and bulk viscosity

  • Henk van Elst
  • Peter K. S. Dunsby
  • Reza Tavakol


Inflationary models and their claim to solve many of the outstanding problems in cosmology have been the subject of a great deal of debate over the last few years. A major sticking point has been the lack of both good observational and theoretical arguments to single out one particular model out of the many that solve these problems. Here we examine the degree of restrictiveness on the dynamical relationship between the cosmological scale factor and the inflation driving self-interaction potential of a minimally coupled scalar field, imposed by the condition that the scalar field is required to be real during a classical regime (the reality condition). We systematically look at the effects of this constraint on many of the inflationary models found in the literature within the FLRW framework, and also look at what happens when physically motivated perturbations such as shear and bulk viscosity are introduced. We find that in many cases, either the models are totally excluded or the reality condition gives rise to constraints on the scale factor and on the various parameters of the model.


Viscosity Scalar Field Differential Geometry Reality Condition Theoretical Argument 
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Copyright information

© Plenum Publishing Corporation 1995

Authors and Affiliations

  • Henk van Elst
    • 1
  • Peter K. S. Dunsby
    • 1
    • 2
  • Reza Tavakol
    • 1
  1. 1.School of Mathematical SciencesQueen Mary and Westfield CollegeLondonUK
  2. 2.Department of Applied MathematicsUniversity of Cape TownCape TownSouth Africa

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