1999 (IPP)

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    Global monopole as dual-vacuum solution in kaluza-klein spacetime
    (2015-03-01) Dadhich, Naresh; Patel, L.K.; Tikekar, R.
    By application of the duality transformation, which implies interchange of active and passive electric parts of the Riemann curvature (equivalent to interchange of Ricci and Einstein tensors) it is shown that the global monopole solution in the Kaluza-Klein spacetime is dual to the corresponding vacuum solution. Further we also obtain solution dual to flat space which would in general describe a massive global monopole in 4-dimensional Euclidean space and would have massless limit analogus to the 4-dimensional dual-flat solution.
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    Generating lambda from the vacuum
    (2015-03-01) Sahni, Varun
    The close relationship between the cosmological constant and the vacuum has been emphasised in the past by Zeldovich amongst others. We briefly discuss different approaches to the cosmological constant issue including the possibility that A could be generated by vacuum polarization in a static Universe. Fresh possibilities occur in an expanding Universe. An Inflationary Universe generically leads to particle creation from the vacuum, the nature and extent of particle production depending upon the mass of the field and ~ts coupling to gravity. For ultra-light, non-minimally coupled scalar fields, particle production can be large and the resulting vacuum energy-momentum tensor will have the form of an effective cosmological constant. The Inflationary scenario therefore, could give rise to a Universe that is both flat and A-dominated, in agreement with observations.