Expanding covariant cosmography of the local universe: incorporating the snap and axial symmetry

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dc.contributor.authorMaartens, Roy
dc.contributor.authorClarkson, Chris
dc.contributor.authorKalbouneh, Basheer
dc.date.accessioned2025-07-30T10:31:34Z
dc.date.available2025-07-30T10:31:34Z
dc.date.issued2025
dc.description.abstractStudies show that the model-independent, fully non-perturbative covariant cosmographic approach is suitable for analyzing the local Universe (z ≲ 0.1). However, accurately characterizing large and inhomogeneous mass distributions requires the fourth-order term in the redshift expansion of the covariant luminosity distance dL (zn ). We calculate the covariant snap parameter S and its spherical harmonic multipole moments using the matter expansion tensor and the evolution equations for lightray bundles. The fourth-order term adds 36 degrees of freedom, since the highest independent multipole of the snap is the 32-pole (dotriacontapole) (ℓ=5). Including this term helps to de-bias estimations of the covariant deceleration parameter. Given that observations suggest axially symmetric anisotropies in the Hubble diagram for z ≲ 0.1 and theory shows that only a subset of multipoles contributes to the signal, we demonstrate that only 12 degrees of freedom are needed for a model-independent description of the local universe. We use an analytical axisymmetric model of the local Universe, with data that matches the Zwicky Transient Facility survey, in order to provide a numerical example of the amplitude of the snap multipoles and to forecast precision.
dc.identifier.citationKalbouneh, B., Santiago, J., Marinoni, C., Maartens, R., Clarkson, C. and Sarma, M., 2025. Expanding covariant cosmography of the local universe: incorporating the snap and axial symmetry. Journal of Cosmology and Astroparticle Physics, 2025(02), p.076.
dc.identifier.urihttps://doi.org/10.1088/1475-7516/2025/02/076
dc.identifier.urihttps://hdl.handle.net/10566/20632
dc.language.isoen
dc.publisherInstitute of Physics
dc.subjectCosmic flows
dc.subjectCosmological parameters from LSS
dc.subjectCosmological simulations
dc.subjectAxial symmetry
dc.subjectCovariant deceleration
dc.titleExpanding covariant cosmography of the local universe: incorporating the snap and axial symmetry
dc.typeArticle

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