IUCAA Preprints
Permanent URI for this communityhttp://localhost:4000/handle/11007/149
Browse
52 results
Search Results
Item Morphology of clusters and superclusters in N-body simulations of cosmological gravitational clustering(2015-03-13) Sathyaprakash, B.S.; Sahni, Varun; Shandarian, SergeiItem Filaments and pancakes in the IRAS 1.2 jy redshift catalogue(2015-03-13) Sathyaprakash, B.S.; Sahni, Varun; Shandarian, Sergei; Fisher, K.B.Item Does inflationary particle production suggest Ωm< 1 ?(2015-03-13) Sahni, Varun; Habib, SalmanItem The inflationary universe- from theory to observations(2015-03-11) Sahni, VarunItem Shapefinders: a new shape diagnostic for large scale structure(2015-03-11) Sahni, Varun; Sathyaprakash, B.S.; Shandarian, SergeiItem Reconstructing the cosmic equation of state from supernova distances(2015-03-01) Saini, Tarun Deep; Raychaudhuri, Somak; Sahni, Varun; Strarobinsky, A.A.Item Generating lambda from the vacuum(2015-03-01) Sahni, VarunThe 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.Item Evidence for filamentarity in the las campanas redshift survey(2015-03-01) Bharadwaj, Somanath; Sahni, Varun; Sathyaprakash, B.S.; Shandarin, S.F.; Yess, CappItem Gravitational instability in the strongly nonlinear regime: A study of various approximations(2015-02-18) Sathyaprakash, B.S.; Sahni, Varun; Munshi, Dipak; Pogosysn, D.; Melott, A.L.Item Behaviour of lagrangian approximations in spherical voids(2015-02-07) Sahni, Varun; Shandarin, S.F.We study the behaviour of spherical voids in Lagrangian perturbation theories L(n), of which the Zel'dovich approximation is the lowest order solution L(1). We find that at early times higher order L(n), give an increasingly accurate picture of void expansion. However, at late times particle trajectories in L (2) begin to turnaround and converge leading to the contraction of a void, a sign of pathological behaviour. By contrast particle trajectories in L(3) are well behaved and this approximation gives results in excellent agreement with the exact top-hat solution as long as the void is not too underdense. For very underdense voids, L (3) evacuates the void much too rapidly, leading us to conclude that the Zel'dovich approximation L(1) remains the best approximation to apply to the late-time study of voids. The behaviour of high-order Lagrangian approximations in spherical voids is typical for asymptotic (semiconvergent) series and may be generic for Lagrangian perturbation theory.