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Browsing by Subject "Dark matter"

Browsing by Subject "Dark matter"

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  • 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 ...
  • MONG: An extension to galaxy clusters 
    Rebecca, Louise; Kenath, Arun; Sivaram, C (World Scientific Publishing, 2022-04-30)
    The presence of dark matter (DM), though well established by indirect evidence, is yet to be observed directly. Various DM detection experiments running for several years have yielded no positive results. In view of these ...
  • The mystery of the cosmic diffuse ultraviolet background radiation 
    Henry, R. C; Murthy, J; Overduin, James; Tyler, Joshua (IOP Publishing Ltd, 2015-01-01)
    The diffuse cosmic background radiation in the Galaxy Evolution Explorer far-ultraviolet (FUV, 1300-1700 Å) is deduced to originate only partially in the dust-scattered radiation of FUV-emitting stars: the source of a ...
  • Near-infrared and optical imaging of Q2345+007: The largest gravitationally lensed QSO system? 
    Gopal-Krishna; Yates, M; Wiita, P. J; Smette, A; Pati, A. K; Altieri, B (The European Southern Observatory, 1993-12)
    We have taken K, R, V, and B band images of Q 2345+007, which has been claimed to be the gravitationally lensed quasar with the widest separation between the two images (approximately equal 7 arcsec), although the lens ...
  • Nonthermal warm dark matter limits from small-scale structure 
    Banerjee, Arka; Das, Subinoy; Maharana, Anshuman; Nadler, Ethan O.; Sharma, Ravi Kumar (American Physical Society, 2023-08-15)
    We present small-scale structure constraints on sterile dark matter produced from a heavy mediator particle, inspired by models of moduli decay. Dark matter particles produced through this mechanism can contribute to the ...
  • The origin of dark matter and its estimate in the metagalaxy 
    Srivastava, D. N (Astronomical Society of India, 1993)
    On dark matter, whereas current research is in the field of weakly interacting particles, this work puts forward a different line of approach. It interprets dark matter as a transformation of matter by a generalized ...
  • Planet nine, dark matter and MOND 
    Sivaram, C; Arun, K; Kiren, O. V (Springer, 2016-07)
    Here we propose the possibility that the recently postulated Neptune-sized planet with an orbital period of 15,000 years could be a gravitationally condensed dark matter (DM) object. The observed mass of Planet Nine fits ...
  • Primordial planets predominantly of dark Matter 
    Sivaram, C; Arun, K; Kiren, O. V (Springer, 2019-05)
    Cosmic structure formation is thought to occur as a bottom-up scenario, i.e. the lightest objects would have formed first. It has been suggested that the earliest structures to form could have been primordial planets. Here ...
  • Relics of the cosmological QCD phase transition 
    Bhattacharyya, A; Alam, J. E; Sarkar, S; Roy, P; Sinha, B; Raha, S; Bhattacharjee, P (The American Physical Society, 2000-04)
    The abundance and size distribution of quark nuggets ~QN’s!, formed a few microseconds after the big bang due to a first-order QCD phase transition in the early universe, has been estimated. It appears that stable QN’s could ...
  • Small scale clustering of late forming dark matter 
    Agarwal, S; Corasaniti, P.-S; Das, Subinoy; Rasera, Y (The American Physical Society, 2015-09-15)
    We perform a study of the nonlinear clustering of matter in the late-forming dark matter (LFDM) scenario in which dark matter results from the transition of a nonminimally coupled scalar field from radiation to collisionless ...
  • A study of the effect of bulges on bar formation in disc galaxies 
    Kataria, Sandeep Kumar; Mousumi Das (Oxford University Press on behalf of the Royal Astronomical Society, 2018-04)
    We use N-body simulations of bar formation in isolated galaxies to study the effect of bulge mass and bulge concentration on bar formation. Bars are global disc instabilities that evolve by transferring angular momentum ...
  • A study of the effect of bulges on bar formation in disc galaxies 
    Kataria, Sandeep Kumar; Mousumi Das (Oxford University Press on behalf of the Royal Astronomical Society, 2018-04)
    We use N-body simulations of bar formation in isolated galaxies to study the effect of bulge mass and bulge concentration on bar formation. Bars are global disc instabilities that evolve by transferring angular momentum ...

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