Browsing Faculty of Natural Sciences by Author "Umeh, Obinna"
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Consequences of using a smooth cosmic distance in a lumpy Universe. I.
Umeh, Obinna (American Physical Society, 2022)How do we appropriately fit a model based on an idealised Friedmann-Lemaˆıtre Robertson-Walker spacetime to observations made from a single location in a lumpy Universe? We address this question for surveys that measure ... -
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 ... -
Nonlinear modulation of the HI power spectrum on ultra-large scales. I
Umeh, Obinna; Maartens, Roy; Santos, Mario G. (IOP Science, 2015)Intensity mapping of the neutral hydrogen brightness temperature promises to provide a three-dimensional view of the universe on very large scales. Nonlinear effects are typically thought to alter only the small-scale ... -
The observed galaxy bispectrum from single-field inflation in the squeezed limit
Koyama, Kazuya; Umeh, Obinna; Maartens, Roy; Bertacca, Daniele (IOP Publishing, 2018)Using the consistency relation in Fourier space, we derive the observed galaxy bispectrum from single- eld in ation in the squeezed limit, in which one of the three modes has a wavelength much longer than the other two. ...