2001 (IPP)

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Author: search.filters.author.Souradeep, Tarun

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    Relic gravity waves from Braneworld inflation
    (2001-10-02) Sahni, Varun; Sami, M.; Souradeep, Tarun
    We discuss a scenario in which extra dimensional effects allow a scalar field with a steep potential to play the dual role of the inflaton as well as dark energy (quintessence). The post-inflationary evo- lution of the universe in this scenario is generically characterised by a ‘kinetic regime’ during which the kinetic energy of the scalar field greatly exceeds its potential energy resulting in a ‘stiff’ equa- tion of state for scalar field matter Pφ ≃ ρφ. The kinetic regime precedes the radiation dominated epoch and introduces an important new feature into the spectrum of relic gravity waves created quantum mechanically during inflation. The amplitude of the gravity wave spectrum increases with wavenumber for wavelengths shorter than the comoving horizon scale at the commencement of the radiative regime. This ‘blue tilt’ is a generic feature of models with steep potentials and imposes strong constraints on a class of inflationary braneworld models. Prospects for detection of the grav- ity wave background by terrestrial and space-borne gravity wave observatories such as LIGO II and LISA are discussed.
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    Window function for non-circular beam CMB anisotropy experiment
    (2001-07-05) Souradeep, Tarun; Ratra, Bharat
    We develop computationally rapid methods to compute the window function for a cosmic microwave background anisotropy experiment with a non-circular beam which scans over large angles on the sky. To concretely illustrate these methods we compute the window function for the Python V experiment which scans over large angles on the sky with an elliptical Gaussian beam.
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    Binned cosmic microwave background anisotropy power spectra : Peak location
    (2001-02-15) Podariu, Silviu; Souradeep, Tarun; Gott, J. Richard; et al.
    We use weighted mean and median statistics techniques to combine individual cosmic microwave background (CMB) anisotropy detections and determine binned, multipole- space, CMB anisotropy power spectra. The resultant power spectra are peaked. The derived weighted-mean CMB anisotropy power spectrum is not a good representation of the individual measurements in a number of multipole-space bins, if the CMB anisotropy is Gaussian and correlations between individual measurements are small. This could mean that some observational error bars are underestimated, possibly as a consequence of undetected systematic effects. Discarding the most discrepant 5% of the measure- ments alleviates but does not completely resolve this problem. The median-statistics power spectrum of this culled data set is not as constraining as the weighted-mean power spectrum. Nevertheless it indicates that there is more power at multipoles ℓ ∼ 150 − 250 than is expected in an open cold dark matter (CDM) model, and it is more consistent with a flat CDM model. Unlike the weighted-mean power spectrum, the median-statistics power spectrum at ℓ ∼ 400 − 500 does not exclude a second peak in the flat CDM model.