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Browsing by Subject "Early universe"

Browsing by Subject "Early universe"

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  • Collapsing void in an expanding universe 
    Mandal, D. R; Banerji, S (Astronomical Soceity of India, 1996)
    We consider here the model of a spherical void in an expanding Robertson - Walker (RW) universe with flat space sections. The void is taken as a sphere of low density conducting perfect fluid (Region I) surrounded by a ...
  • Deep J -band imaging of high redshift QSO candidates with the Himalayan Chandra Telescope 
    Goto, T; Ojha, D (Astronomical Society of India, 2006)
    High redshift QSOs (redshift >5.7) are highly important ob jects. If such QSOs may be found, their spectra will reveal the onset of reionization of the intergalactic medium (Gunn-Peterson trough), and provide precious in ...
  • Effects of dark matter in star formation 
    Arun, K; Gudennavar, S; Prasad, A; Sivaram, C (Springer, 2019-02)
    The standard model for the formation of structure assumes that there existed small fluctuations in the early universe that grew due to gravitational instability. The origins of these fluctuations are as yet unclear. In ...
  • Enigmatic aspects of the early universe: possibility of a `pre-big bang phase'! 
    Sivaram, C; Arun, K (Springer, 2011-05)
    In this paper it is suggested that inclusion of mutual gravitational interactions among the particles in the early dense universe can lead to a ‘pre-big bang’ scenario, with particle masses greater than the Planck mass ...
  • A faster growth of perturbations in an early matter dominated epoch: primordial black holes and gravitational waves 
    Das, Subinoy; Maharana, Anshuman; Muia, Francesco (Oxford University Press on behalf of Royal Astronomical Society, 2022-09)
    We present a scenario for fast growth of cosmological perturbations; δ(t) ∼ a(t)s, a(t) being the scale factor, with s > 10 for the numerical examples reported in this article. The basic ingredients of the scenario are an ...
  • Formation and Abundance of Late-forming Primordial Black Holes as Dark Matter 
    Chakraborty, Amlan; Chanda, Prolay K; Pandey, Kanhaiya L; Das, Subinoy (American Astronomical Society, 2022-06-20)
    We propose a novel mechanism where primordial black hole (PBH) dark matter is formed much later in the history of the universe, between the epochs of Big Bang nucleosynthesis and cosmic microwave background photon decoupling. ...
  • Forming supermassive black holes like J1342+0928 (invoking dark matter) in early universe 
    Sivaram, C; Arun, K; Kiren, O. V (Springer, 2018-02)
    Recent discovery of J1342+0928 using data from the WISE telescope and ground based surveys indicate presence of a supermassive black hole (SMBH) having a mass of 800 million solar mass at a redshift of about 7.6. This imply ...
  • Hot and cold spot counts as probes of non-gaussianity in the cosmic microwave background 
    Pravabati, C; Park, C; Yogendran, K. P; van de Weygaert, R (IOP Publishing, 2012-08-20)
    We introduce the numbers of hot and cold spots, n/subh/ and n/subc/, of excursion sets of the cosmic microwave background (CMB) temperature anisotropy maps as statistical observables that can discriminate different ...
  • Physics of Structure Formation in the Universe 
    Choudhury, T. R (Astronomical Society of India, 2003)
    In recent years, unprecedented progress in observational cosmology has revealed a great deal of information about the formation and evolution of structures in the universe. This, in turn, has raised many challenging issues ...
  • Search for HI Reionization Epoch in the Early Universe 
    Swarup, G (Astronomical Society of India, 2003)
    One of the most challenging problems in astronomy today is to search for reionization of the neutral hydrogen (HI), which is expected to occur somewhere between redshifts of about 6 to 20. The reionization is likely to ...

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