ORCID Profile
0000-0002-4578-4019
Current Organisation
Institut de Physique des 2 Infinis de Lyon
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Publisher: Oxford University Press (OUP)
Date: 10-10-2023
Publisher: Oxford University Press (OUP)
Date: 12-01-2023
Abstract: The ability to test and constrain theories of cosmic inflation will advance substantially over the next decade. Key data sources include cosmic microwave background (CMB) measurements and observations of the distribution of matter at low-redshift from optical, near-infrared, and 21-cm intensity surveys. A positive detection of a CMB B-mode consistent with a primordial stochastic gravitational wave background (SGWB) is widely viewed as a smoking gun for an inflationary phase. Still, a null result does not exclude inflation. However, in a significant class of inflationary scenarios, a low SGWB litude is correlated with a more significant running, αs, in the primordial density perturbations than is seen with the simplest inflationary potentials. With this motivation, we forecast the precision with which the spectral index ns and αs can be constrained by currently envisaged observations, including CMB (Simons Observatory, CMB-S4 and LiteBIRD), optical/near infra-red (DESI and SPHEREx), and 21-cm intensity mapping (Tianlai and CHIME) surveys. We identify optimal combinations of data sets for constraining the running and show that they may yield additional and informative constraints on the overall inflationary parameter space if the SGWB remains undetected.
Publisher: Oxford University Press (OUP)
Date: 29-07-2022
Abstract: The evolution of the gravitational potentials on large scales due to the accelerated expansion of the Universe is an important and independent probe of dark energy, known as the integrated Sachs–Wolfe (ISW) effect. We measure this ISW effect through cross-correlating the cosmic microwave background maps from the Planck satellite with a radio continuum galaxy distribution map from the recent Rapid ASKAP Continuum Survey (RACS). We detect a positive cross-correlation at $\\sim 2.8\\, \\sigma$ relative to the null hypothesis of no correlation. We parametrize the strength of the ISW effect through an litude parameter and find the constraints to be $A_{\\mathrm{ISW}} = 0.94^{+0.42}_{-0.41}$, which is consistent with the prediction of an accelerating universe within the current concordance cosmological model, ΛCDM. The credible interval on this parameter is independent of the different bias models and redshift distributions that were considered when marginalizing over the nuisance parameters. We also detect a power excess in the galaxy autocorrelation angular power spectrum on large scales (ℓ ≤ 40), and investigate possible systematic causes.
Publisher: American Physical Society (APS)
Date: 09-09-2022
Publisher: Oxford University Press (OUP)
Date: 22-06-2023
Abstract: The position of the peak of the matter power spectrum, the so-called turnover scale, is set by the horizon size at the epoch of matter-radiation equality. It can easily be predicted in terms of the physics of the universe in the relativistic era, and so can be used as a standard ruler, independent of other features present in the matter power spectrum, such as baryon acoustic oscillations (BAOs). We use the distribution of quasars measured by the extended Baryon Oscillation Spectroscopic Survey (eBOSS) to determine the turnover scale in a model-independent fashion statistically. We avoid modelling the BAO by down-weighting affected scales in the covariance matrix using the mode deprojection technique. We measure the wavenumber of the peak to be $k_\\mathrm{TO} = \\left(17.6^{+1.9}_{-1.8} \\right) \\times 10^{-3}h/\\mathrm{Mpc}$, corresponding to a dilation scale of $D_\\mathrm{V}(z_\\mathrm{eff} = 1.48) = \\left(31.1^{+4.1}_{-3.4}\\right)r_\\mathrm{H}$. This is not competitive with current BAO distance measures in terms of determining the expansion history but does provide a useful cross-check. We combine this measurement with low-redshift distance measurements from type-Ia supernova data from Pantheon and BAO data from eBOSS to make a sound-horizon free estimate of the Hubble–Lemaître parameter and find it to be $H_0=64.8^{+8.4}_{-7.8} \\ \\mathrm{km/s/Mpc}$ with Pantheon, and $H_0=63.3^{+8.2}_{-6.9} \\ \\mathrm{km/s/Mpc}$ with eBOSS BAO. We make predictions for the measurement of the turnover scale by the Dark Energy Spectroscopic Instrument (DESI) survey, the Maunakea Spectroscopic Explorer (MSE), and MegaMapper, which will make more precise and accurate distance determinations.
Location: United Kingdom of Great Britain and Northern Ireland
Location: Korea, Republic of
No related grants have been discovered for Benedict Bahr-Kalus.