1998 (IPP)
Permanent URI for this collectionhttp://localhost:4000/handle/11007/2980
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Item Classical essence of black hole radiation(2015-03-14) Nouri-Zonoz, M.; Padmanabhan, T.Item Nonlinear density evolution from an improved spherical collapse model(2015-03-14) Engineer, Sunu; Kanekar; Padmanabhan, T.Item Doing it with mirrors : Classical analogues for black hole radiation(2015-03-14) Srinivasan, K.; Padmanabhan, T.Item Particle production and complex path analysis(2015-03-13) Srinivasan, K.; Padmanabhan, T.Item Facets of tunneling: Particle production in external fields(2015-03-11) Srinivasan, K.; Padmanabhan, T.Item Possible Newtonian interpretation of relativistic cosmological perturbation theory(2015-03-11) Nayeri, Ali; Padmanabhan, T.Cosmological perturbations with wavelengths smaller than Hubble radius can be handled in the context of Newtonian theory with very high accuracy. The application of this Newtonian approximation, however, is restricted to nonrelativistic matter and cannot be used for relativistic matter. Recently, by modifying the continuity equation, Lima, et. a!., extended the domain of applicability of Newtonian cosmology to radiation dominated phase. We adopted this continuity equation to re-examine linear cosmological perturbation theory for a two fluid universe with uniform pressure. We study the evolution equations for density contrasts and their validity in different epochs and on scales larger than Hubble radius and compare the results with the full relativistic approach. The comparison shows the high accuracy of this approximation.Item Formal analysis of two dimensional gravity(2015-03-11) Engineer, Sunu; Srinivasan, K.; Padmanabhan, T.Several investigations in the study of cosmological structure formation use numerical simulations in both two and three dimensions. In this paper we address the subtle question of ambiguities in the nature of two dimensional gravity in an expanding background. We take a detailed and formal approach by deriving the equations describing gravity in (D + 1) dimensions using the action principle of Einstein. We then consider the Newtonian limit of these equations and finally obtain the necessary fluid equations required to describe structure formation. These equations are solved for the density perturbation in both the linearised form and in the spherical top hat model of nonlinear growth. We find that, when the special case of D = 2 is considered, no structures can grow. We therefore conclude that, within the frame work of Einstein's theory of gravity in (2 + 1) dimensions, formation of structures cannot take place. Finally, we indicate the different possible ways of getting around this difficulty so that growing structures can be obtained in two dimensional cosmological gravitational simulations and discuss their implications.Item Event horizon: Magnifying glass for planck length physics(2015-03-11) Padmanabhan, T.Item Quantum structure of spacetime and blackhole entropy(2015-02-11) Padmanabhan, T.