Browsing by Author "Maartens, Roy"
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Antilensing: 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 underdense 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 nonGaussianity by combining nextgeneration 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 nonGaussianity that is generated in the primordial universe. This primordial signal survives only on the largest scales where cosmic variance ... 
Constraining primordial nongaussianity by combining nextgeneration 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 nonGaussianity 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, JanAlbert; Fonseca, Jos´e; Maartens, Roy (IOP Publishing, 2020)The growth rate of largescale 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 nextgeneration cosmological data sets. We study the possibility of detecting the total neutrino mass using largescale 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; BenoitLevy, Aurelien; Joachimi, Benjamin; Kirk, Donnacha; Klöckner, HansRainer; Raccanelli, Alvise; Santos, Mario G.; Zhao, GongBo (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 ultralarge 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; VillaescusaNavarro, 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 largescale 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 leadingorder relativistic corrections, due to Doppler, gravitational redshift and related lineofsight effects in redshift space. The detection ... 
Disentangling nongaussianity, bias, and general relativistic effects in the galaxy distribution
Bruni, Marco; Crittenden, Robert; Maartens, Roy (American Physical Society, 2012)Local nonGaussianity, parametrized by f NL , introduces a scaledependent 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)NonGaussianity 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 Hubblescale inhomogeneity. In these models, density perturbations grow on a radially inhomogeneous background. ... 
The Hubble constant tension with nextgeneration 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 horizonscale effects with multiwavelength surveys
Fonseca, Jose; Camera, Stefano; Santos, Mario G.; Maartens, Roy (American Astronomical Society, 2015)Nextgeneration 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 largescale 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 redshiftspace 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, GongBo (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 ... 
Modelindependent constraints on dark energy and modified gravity with the SKA
Zhao, GongBo; 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 ...