7 papers
Les Houches on Dark Universe 2025: Elements of cosmology beyond FLRW
Pierre Fleury
Modern cosmology is based on the cosmological principle, which states that the Universe is statistically homogeneous and isotropic. When applied in its strict -- rather than statis…
Cosmology with the line-of-sight shear of strong gravitational lenses
Pierre Fleury, Daniel Johnson, Théo Duboscq +2
Stage-IV photometric galaxy surveys are designed to measure the position and shapes of billions of galaxies. Their aim is to characterise the large-scale distribution of matter in…
Degeneracies and modelling choices in double-plane time-delay cosmography
Daniel Johnson, Pierre Fleury, Martin Millon
Double-plane gravitational lensing is a rare but increasingly observed phenomenon in which the light from a distant source is lensed by two foreground objects at different redshift…
Emergent Cosmological Expansion in Scalar-Tensor Theories of Gravity
Chad Briddon, Timothy Clifton, Pierre Fleury
We consider the emergence of large-scale cosmological expansion in scalar-tensor theories of gravity. This is achieved by modelling sub-horizon regions of space-time as weak-field…
Line-of-sight effects on double source plane lenses
Daniel Johnson, Thomas Collett, Tian Li +1
Weak gravitational lensing perturbations have a non-negligible impact on strong lensing observables, and several degeneracies exist between the properties of the main lens, line of…
Sparsity covariance: a source of uncertainty when estimating correlation functions with a discrete sample of observations in the sky
Pierre Fleury
Cosmological observables rely heavily on summary statistics such as two-point correlation functions. In many practical cases (e.g. the weak-lensing cosmic shear), those correlation…