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Browsing by Subject "Dark matter"

Browsing by Subject "Dark matter"

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  • A critique on Drexler dark matter 
    Sivaram, C; Arun, K; Nagaraja, R (Springer, 2011-05)
    Drexler dark matter is an alternate approach to dark matter that assumes that highly relativistic protons trapped in the halo of the galaxies could account for the missing mass. We look at various energetics involved in ...
  • Dark matter (energy) may be indistinguishable from modified gravity (MOND) 
    Sivaram, C (World Scientific Publishing Co Pte Ltd, 2017-10)
    For Newtonian dynamics to hold over galactic scales, large amounts of dark matter (DM) are required which would dominate cosmic structures. Accounting for the strong obser- vational evidence that the universe is accelerating ...
  • Dark matter density distributions and dark energy constraints on structure formation including MOND 
    Rebecca, L; Arun, K; Sivaram, C (Springer, 2020-09)
    In recent papers, it was shown explicitly that the sizes of gravitationally bound large-scale cosmic structures can be constrained from the requirement that their gravitational binding self-energy density should at least ...
  • Dark Matter Objects: Possible New Source of Gravitational Waves 
    Sivaram, C; Arun, K (Springer, 2019-10)
    Gravitational waves from mergers of black holes and neutron stars are now being detected by LIGO. Here we look at a new source of gravitational waves, i.e., a class of dark matter objects whose properties were earlier ...
  • Dark matter, dark energy, and alternate models: A review 
    Arun, k; Gudennavar, S.B; Sivaram, C (Elsevier B.V, 2017-07)
    The nature of dark matter (DM) and dark energy (DE) which is supposed to constitute about 95% of the energy density of the uni-verse is still a mystery. There is no shortage of ideas regarding the nature of both. While ...
  • Effects of dark matter in red giants 
    Clea, Sunny; Sivaram, C; Gudennavar, S. B (Elsevier B. V., 2020-12)
    Dark matter (DM) which constitutes five-sixths of all matter is hypothesized to be a weakly interacting non-baryonic particle, created in the early stages of cosmic evolution. It can affect various cosmic structures in the ...
  • 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 ...
  • Effects of dark matter on the upper bound mass of neutron stars 
    Kumar, S. S; Kenath, A; Sivaram, C (Elsevier B.V, 2020-05)
    Observations have indicated that we do not see neutron stars (NS) of mass near the theoretical upper limit as predicted. Here we invoke the role of dark matter (DM) particles in star formation, and their role in lowering ...
  • Enhanced star formation in the cometary globules of the GUM nebula 
    Bhatt, H. C (Royal Astronomical Society, 1993-06-01)
    Evidence for an enhanced rate of star formation in the cometary globules of the Gum nebula is presented. The IRAS Point Source Catalog has been searched for sources with spectral energy distributions characteristic of young ...
  • Evolution of primordial dark matter planets in the early Universe 
    Kiren, O. V; Arun, K; Sivarani, C (Elsevier B. V, 2021-08-15)
    In a recent paper we had discussed possibility of DM at high redshifts forming primordial planets composed entirely of DM to be oneof the reasons for not detecting DM (as the flux of ambient DM particles would be consequently ...
  • Extremal charged black holes, dark matter and dark energy 
    Sivaram, C; Arun, K; Prasad, A (Springer, 2018-10)
    Formation of black holes may be constrained by intrinsic parameters characterizing them such as electric charge. Here we discuss the effects of a relatively minute excess of charge on extremal black hole formation and the ...
  • 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. ...
  • Galaxy formation 
    Padmanabhan, T; Subramanian, K (Astronomical Society of India, 1992)
    An attempt is made to develop a consistent theory describing galaxy formation. First, a discussion of the smooth universe is presented. The linear theory of perturbations is introduced, and its applications are described. ...
  • The Hubble tension: change in dark energy or a case for modified gravity? 
    Sivaram, C; Arun, K; Rebecca, Louise (Springer, 2022-03)
    Recently, much controversy has been raised about the cosmological conundrum involving the discrepancy in the value of the Hubble constant as implied by Planck satellite observations of the CMBR in the early Universe and ...
  • Lower bounds on axion rest mass in a general cosmological scenario 
    Datta, B; Joshi, P. S (Astronomical Society of Indian, 1986-09)
    It is shown that, if axions make up the dark matter in the universe, a general lower limit range of 1.07-4.09 x 10 to the -5th eV can be set on the axion rest mass on the basis of consideration of general spacetimes, without ...
  • The M31 pixel lensing plan campaign: macho lensing and self-lensing signals 
    Novati, S. C; Bozza, V; Bruni, I; Dall'Ora, M; Paolis, F. D; Dominik, M; Gualandi, R; Ingrosso, G; Jetzer, P; Mancini, L; Nucita, A; Safonova, M; Scarpetta, G; Sereno, M; Strafella, F; Subramaniam, A; Gould, A (IOP Publishing, 2014-03-10)
    We present the final analysis of the observational campaign carried out by the PLAN (Pixel Lensing Andromeda) collaboration to detect a dark matter signal in form of MACHOs through the microlensing effect. The campaign ...
  • Minkowski Tensors in Two Dimensions: Probing the Morphology and Isotropy of the Matter and Galaxy Density Fields 
    Appleby, S; Pravabati, C; Park, C; Hong, S. E; Kim, J; Vidhya, G (IOP Publishing, 2018-05-10)
    We apply the Minkowski tensor statistics to two-dimensional slices of the three-dimensional matter density field. The Minkowski tensors are a set of functions that are sensitive to directionally dependent signals in the ...
  • Modelling dark matter halo spin using observations and simulations: application to UGC 5288 
    Ansar, Sioree; Kataria, Sandeep Kumar; Mousumi Das (Oxford University Press on behalf of Royal Astronomical Society, 2023-06)
    Dark matter (DM) halo properties are extensively studied in cosmological simulations but are very challenging to estimate from observations. The DM halo density profile of observed galaxies is modelled using multiple ...
  • MOND, MONG, MORG as alternatives to dark matter and dark energy, and consequences for cosmic structures 
    Sivaram, C; Arun, Kenath; Rebecca, Louise (Indian Academy of Sciences, 2020-02)
    In view of the negative results from various dark matter detection experiments, we propose alternate models by postulating a minimal field strength (minimal curvature) and also a minimal acceleration. These postulates ...

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