Research Papers (TP)
Permanent URI for this collectionhttp://localhost:4000/handle/11007/3
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Item Constraints on the shape of the density spectrum from COBE and galaxy surveys(Wiley-Blackwell, 1992-10-28) Padmanabhan, T.; Narasimha, D.Item WMAP constraints on low redshift evolution of dark energy(Wiley-Blackwell, 2004-10-29) Jassal, H. K.; Bagla, J. S.; Padmanabhan, T.The conceptual difficulties associated with a cosmological constant have led to the investigation of alternative models in which the equation of state parameter, w = p/ρ,of the dark energy evolves with time. We show that combining the supernova type Ia observations with the constraints from WMAP observations restricts large variation of ρ(z)atlow redshifts. The combination of these two observational constraints is stronger than either one. The results are completely consistent with the cosmological constant as the source of dark energy.Item Temperature fluctuations of cosmic microwave background induced by gravitational lensing(Elsevier Science Publishers, 1986-08-25) Chitre, S. M.; Narlikar, J. V.; Padmanabhan, T.Adopting the accepted interpretation of the cosmic microwave background (CMBR) as a relic of the early hot universe we show that any angular intensity variations existing in the background at the "last scattering surface" at the redshift of ~10³ will induce bright fluctuations through gravitational lensing by intervening masses. The resulting temperature variations ΔT are estimated for gravitating masses like distant galaxies (z ~1) and local dark objects (e.g. population III stars) in our own Galaxy. It is found that the value of ΔT/T produced by the above mechanisms further constrains the theories of galaxy formation. The calculation also limits the amount of matter present in the form of population III objects in the galaxy.