A fast semidiscrete optimal transport algorithm for a unique reconstruction of the early Universe
Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) 506:1 (2021) 1165-1185
Model-independent constraints on clustering and growth of cosmic structures from BOSS DR12 galaxies in harmonic space
ArXiv preprint. 14 pages, 8 figures, 3 tables
Abstract:
We present a new, model-independent measurement of the clustering amplitude of galaxies and the growth of cosmic large-scale structures from the Baryon Oscillation Spectroscopic Survey (BOSS) 12th data release (DR12). This is achieved by generalising harmonic-space power spectra for galaxy clustering to measure separately the magnitudes of the density and of the redshift-space distortion terms, which are respectively related to the clustering amplitude, bσ8(z), and the growth, fσ8(z). We adopt a tomographic approach with 15 redshift bins in the range z∈[0.15,0.67]. We restrict our analysis to strictly linear scales, implementing a redshift-dependent maximum multipole for each of the tomographic bins. Thus, we obtain 30 data points in total, 15 for each of the quantities bσ8(z) and fσ8(z). The measurements do not appear to suffer from any apparent systematic effect and show excellent agreement with the theoretical prediction from a concordance cosmology as from the Planck satellite. Our results also agree with previous analyses by the BOSS collaboration. Although each single datum has, in general, a larger error bar than that obtained in configuration- or Fourier-space analyses, our study provides the community with a larger number of tomographic data points that allow for a complementary tracking in redshift of the evolution of fundamental cosmological quantities.
Constraints on Equivalence Principle Violation from Gamma Ray Bursts
(2021)
Constraints on equivalence principle violation from gamma ray bursts
Physical Review D American Physical Society 104 (2021) 084025
Abstract:
Theories of gravity that obey the Weak Equivalence Principle have the same Parametrised Post-Newtonian parameter $\gamma$ for all particles at all energies. The large Shapiro time delays of extragalactic sources allow us to put tight constraints on differences in $\gamma$ between photons of different frequencies from spectral lag data, since a non-zero $\Delta \gamma$ would result in a frequency-dependent arrival time. The majority of previous constraints have assumed that the Shapiro time delay is dominated by a few local massive objects, although this is a poor approximation for distant sources. In this work we consider the cosmological context of these sources by developing a source-by-source, Monte Carlo-based forward model for the Shapiro time delays by combining constrained realisations of the local density field using the Bayesian origin reconstruction from galaxies algorithm with unconstrained large-scale modes. Propagating uncertainties in the density field reconstruction and marginalising over an empirical model describing other contributions to the time delay, we use spectral lag data of Gamma Ray Bursts from the BATSE satellite to constrain $\Delta \gamma < 2.1 \times 10^{-15}$ at $1 \sigma$ confidence between photon energies of $25 {\rm \, keV}$ and $325 {\rm \, keV}$.Linear anisotropies in dispersion-measure-based cosmological observables
Physical Review D - Particles, Fields, Gravitation and Cosmology American Physical Society 103 (2021) 123544