Now showing items 1-20 of 30

    • Anti-lensing: the bright side of voids 

      Bolejko, Krzysztof; Clarkson, Chris; Maartens, Roy; Bacon, David; Meures, Nikolai; Beynon, Emma (American Physical Society, 2013)
      More than half of the volume of our Universe is occupied by cosmic voids. The lensing magni ca- tion e ect from those under-dense regions is generally thought to give a small dimming contribution: objects on the far side ...
    • Clustering of quintessence on horizon scales and its imprint on HI intensity mapping 

      Duniya, Didam G.A.; Bertacca, Daniele; Maartens, Roy (IOP Science, 2013)
      Quintessence can cluster only on horizon scales. What is the effect on the observed matter distribution? To answer this, we need a relativistic approach that goes beyond the standard Newtonian calculation and deals properly ...
    • Constraining primordial non-Gaussianity by combining next-generation galaxy and 21 cm intensity mapping surveys 

      Sheean, Jolicoeur; Maartens, Roy; Jolicoeur, Sheean; Dlamini, Simthembile (Institute for Ionics, 2023)
      Surveys of the matter distribution contain ‘fossil’ information on possible non-Gaussianity that is generated in the primordial universe. This primordial signal survives only on the largest scales where cosmic variance ...
    • Constraining primordial non-gaussianity by combining next-generation galaxy and 21 cm intensity mapping surveys 

      Jolicoeur, Sheean; Maartens, Roy; Dlamini, Simthembile (SpringerOpen, 2023)
      Surveys of the matter distribution contain ‘fossil’ information on possible non-Gaussianity that is generated in the primordialUniverse. This primordial signal survives only on the largest scales where cosmic variance ...
    • Constraining the growth rate by combining multiple future surveys 

      Viljoen, Jan-Albert; Fonseca, Jos´e; Maartens, Roy (IOP Publishing, 2020)
      The growth rate of large-scale structure provides a powerful consistency test of the standard cosmological model and a probe of possible deviations from general relativity. We use a Fisher analysis to forecast constraints ...
    • Constraining the neutrino mass using a multitracer combination of two galaxy surveys and cosmic microwave background lensing 

      Ballardini, Mario; Maartens, Roy (Oxford University Press, 2022)
      Measuring the total neutrino mass is one of the most exciting opportunities available with next-generation cosmological data sets. We study the possibility of detecting the total neutrino mass using large-scale clustering ...
    • Cosmological constraints from the power spectrum and bispectrum of 21cm intensity maps 

      Karagiannis, Dionysios; Maartens, Roy; Randrianjanahary, Liantsoa F. (IOP Publishing, 2022)
      The 21cm emission of neutral hydrogen is a potential probe of the matter distribution in the Universe after reionisation. Cosmological surveys of this line intensity will be conducted in the coming years by the SKAO and ...
    • Cosmology from HI galaxy surveys with the SKA 

      Maartens, Roy; Abdalla, Filipe B.; Bull, Philip; Camera, Stefano; Benoit-Levy, Aurelien; Joachimi, Benjamin; Kirk, Donnacha; Klöckner, Hans-Rainer; Raccanelli, Alvise; Santos, Mario G.; Zhao, Gong-Bo (Proceedings of Science, 2014)
      The Square Kilometer Array (SKA) has the potential to produce galaxy redshift surveys which will be competitive with other state of the art cosmological experiments in the next decade. In this chapter we summarise what ...
    • Cosmology on the largest scales with the SKA 

      Camera, Stefano; Raccanelli, Alvise; Bull, Philip; Bertacca, Daniele; Chen, Xuelei; Ferreira, Pedro G.; Kunz, Martin; Maartens, Roy; Mao, Yi; Santos, Mario G.; Shapiro, Paul R.; Viel, Matteo; Xug, Yidong (Proceedings of Science, 2014)
      The study of the Universe on ultra-large scales is one of the major science cases for the Square Kilometre Array (SKA). The SKA will be able to probe a vast volume of the cosmos, thus representing a unique instrument, ...
    • Cosmology with a SKA HI intensity mapping survey 

      Santos, Mario G.; Bull, Philip; Alonso, David; Camera, Stefano; Ferreira, Pedro G.; Bernardi, Gianni; Maartens, Roy; Viel, Matteo; Villaescusa-Navarro, Francisco; Abdalla, Filipe B.; Jarvis, Matt; Metcalf, R. Benton; Pourtsidou, A.; Wolz, Laura (Proceedings of Science, 2014)
      HI intensity mapping (IM) is a novel technique capable of mapping the large-scale structure of the Universe in three dimensions and delivering exquisite constraints on cosmology, by using HI as a biased tracer of the ...
    • Detecting the relativistic galaxy bispectrum 

      Maartens, Roy; Jolicoeur, Sheean; Umeh, Obinna (IOP Publishing Ltd, 2020)
      The Fourier galaxy bispectrum is complex, with the imaginary part arising from leading-order relativistic corrections, due to Doppler, gravitational redshift and related lineof-sight effects in redshift space. The detection ...
    • Disentangling non-gaussianity, bias, and general relativistic effects in the galaxy distribution 

      Bruni, Marco; Crittenden, Robert; Maartens, Roy (American Physical Society, 2012)
      Local non-Gaussianity, parametrized by f NL , introduces a scale-dependent bias that is strongest at large scales, precisely where general relativistic (GR) effects also become significant. With future data, it should ...
    • Einstein's legacy in galaxy surveys 

      Camera, Stefano; Maartens, Roy; Santos, Mario G. (Oxford University Press, 2015)
      Non-Gaussianity in the primordial fluctuations that seeded structure formation produces a signal in the galaxy power spectrum on very large scales. This signal contains vital information about the primordial Universe, but ...
    • Galaxy correlations and the BAO in a void universe: structure formation as a test of the Copernican Principle 

      February, Sean; Clarkson, Chris; Maartens, Roy (IOP Science, 2013)
      A suggested solution to the dark energy problem is the void model, where accelerated expansion is replaced by Hubble-scale inhomogeneity. In these models, density perturbations grow on a radially inhomogeneous background. ...
    • The Hubble constant tension with next-generation galaxy surveys 

      Bengaly, Carlos A.P.; Clarkson, Chris; Maartens, Roy (IOP Publishing Ltd, 2020)
      The rate at which the universe is expanding today is a fundamental parameter in cosmology which governs our understanding of structure formation and dark energy. However, current measurements of the Hubble constant, H0, ...
    • Hunting down horizon-scale effects with multi-wavelength surveys 

      Fonseca, Jose; Camera, Stefano; Santos, Mario G.; Maartens, Roy (American Astronomical Society, 2015)
      Next-generation cosmological surveys will probe ever larger volumes of the universe, including the largest scales, near and beyond the horizon. On these scales, the galaxy power spectrum carries signatures of local primordial ...
    • Improvements in cosmological constraints from breaking growth degeneracy 

      Perenon, Louis; Ilic, St´ephane; Maartens, Roy (EDP Sciences, 2020)
      The key probes of the growth of a large-scale structure are its rate f and amplitude σ8. Redshift space distortions in the galaxy power spectrum allow us to measure only the combination fσ8, which can be used to constrain ...
    • The kinematic dipole in galaxy redshift surveys 

      Maartens, Roy; Clarkson, Chris; Chen, Song (IOP Publishing, 2018)
      In the concordance model of the Universe, the matter distribution { as observed in galaxy number counts or the intensity of line emission (such as the 21cm line of neutral hydrogen) - should have a kinematic dipole due ...
    • Measuring redshift-space distortion with future SKA surveys 

      Raccanelli, Alvise; Bull, Philip; Camera, Stefano; Bacon, David; Blake, Chris; Dore, Olivier; Ferreira, Pedro G.; Maartens, Roy; Santos, Mario G.; Viel, Matteo; Zhao, Gong-Bo (Proceedings of Science, 2014)
      The peculiar motion of galaxies can be a particularly sensitive probe of gravitational collapse. As such, it can be used to measure the dynamics of dark matter and dark energy as well the nature of the gravitational laws ...
    • Model-independent constraints on dark energy and modified gravity with the SKA 

      Zhao, Gong-Bo; Bacon, David; Maartens, Roy; Santos, Mario G.; Raccanelli, Alvise (Proceedings of Science, 2014)
      Employing a nonparametric approach of the principal component analysis (PCA), we forecast the future constraint on the equation of state w(z) of dark energy, and on the effective Newton constant m(k; z), which parameterise ...