43 citations · 386 across the 32 of their papers we have counts for
33 papers
The Optical Expansion Scalar in Cosmological Perturbation Theory
Alexander Oestreicher, Sofie Marie Koksbang
Within the geometric optics approximation, the optical expansion scalar describes the local rate of change in the amplitude of a wave or the area of a light bundle propagating thro…
Learning the averaged history of an inhomogeneous universe from its present day density field
Jonas Broe Bendtsen, Sofie Marie Koksbang
In this work, we investigate whether machine learning can be used to infer averaged cosmological quantities directly from the present day matter density distribution. Using an impl…
Cosmography for a General Spacetime Centred at Arbitrary Redshift
Jonas Broe Bendtsen, Asta Heinesen, Sofie Marie Koksbang
With upcoming surveys providing large volumes of highly precise observational data across a wide range of redshifts, it is increasingly important to have tools that can translate o…
Wave Optics Effects from Gravitational Wave Propagation Through Dark Matter Halos
Annamalai P. Shanmugaraj, Roland Haas, Erik Schnetter +1
Gravitational wave (GW) propagation is usually studied under the geometric optics approximation. But when GWs propagate through structures of sizes similar to their wavelength, thi…
A First Observational Assessment of Cosmic Backreaction Over an Extended Redshift Range
S. M. Koksbang
In the recent preprint arXiv:2604.07244v1, the authors introduce a novel combination of redshift, distance, and expansion rate observables for constraining cosmic backreaction obse…
Diagnostic Consistency Tests of the Concordance Cosmology
S. M. Koksbang, A. Heinesen
The CDM cosmological model faces increasingly significant and robust tensions among independent cosmological probes, prompting renewed scrutiny of its foundational assumptions.…
Model-independent constraints on generalized FLRW consistency relations with bootstrap-based symbolic regression
S. M. Koksbang, A. Heinesen
The standard CDM cosmological model faces increasing tensions between key observations, motivating tests that probe its underlying assumptions. In a companion letter, we present…
Safely simplifying redshift drift computations in inhomogeneous cosmologies: Insights from LTB Swiss-cheese models
David Rønne Sallingboe, Sofie Marie Koksbang
One of the most important discoveries in cosmology is the accelerated expansion of the Universe. Yet, the accelerated expansion has only ever been measured {\em in}directly. Redshi…
Transverse Velocities in Real-Time Cosmology: Position Drift in Relativistic N-Body Simulations
Alexander Oestreicher, Chris Clarkson, Julian Adamek +1
The era of real-time cosmology has begun. It is now possible to directly measure the apparent drift of high-redshift astronomical sources across the sky . Th…
Redshift Drift in Relativistic N-Body Simulations
Alexander Oestreicher, Chris Clarkson, Julian Adamek +1
The cosmological redshift drift promises to be the first observable directly measuring the evolution of the cosmic expansion rate and should be detectable with upcoming surveys by…
Testing inhomogeneous cosmography in our cosmic neighborhood using CosmicFlows-4
S. M. Koksbang
The convergence of the third order general cosmographic expansion of the luminosity distance is examined using several versions of a semi-realistic model of our local cosmic neighb…
Backreaction in Numerical Relativity: Averaging on Newtonian gauge-like hypersurfaces in Einstein Toolkit cosmological simulations
Alexander Oestreicher, Sofie Marie Koksbang
We introduce a spatial averaging scheme and use it to study the evolution of spatial averages in large-scale simulations of cosmological structure formation performed with the Eins…
On the convergence of cosmographic expansions in Lemaitre-Tolman-Bondi models
Asha B. Modan, S. M. Koksbang
We study cosmographic expansions of the luminosity distance for a variety of Lemaitre-Tolman-Bondi models which we specify inspired by local large-scale structures of the universe.…
cp3-bench: A tool for benchmarking symbolic regression algorithms tested with cosmology
Mattias E. Thing, Sofie M. Koksbang
We introduce cp3-bench, a tool for comparing symbolic regression algorithms which we make publicly available at https://github.com/CP3-Origins/cp3-bench. Currently, cp3-bench inclu…
Redshift drift in a universe with structure III: Numerical relativity
Sofie Marie Koksbang, Asta Heinesen, Hayley J. Macpherson
Measurements of the cosmic redshift drift - the change in redshift of a source over time - will enable independent detection of cosmological expansion thanks to the immense precisi…
Cosmological parameter constraints using phenomenological symbolic expressions: On the significance of symbolic expression complexity and accuracy
S. M. Koksbang
Phenomenological models are widely used in cosmology in relation to constraining different cosmological models, with two common examples being cosmographic expansions and modeling…
Machine learning cosmic backreaction and its effects on observations
S. M. Koksbang
Symbolic expressions for cosmic backreaction and mean redshift drift in a range of 2-region models in terms of average quantities are presented. The demonstration that these expres…
Cosmic backreaction and the mean redshift drift from symbolic regression
S. M. Koksbang
The possibility of obtaining symbolic expressions for cosmic backreaction is explored through a case study of so-called 2-region models. By using the publicly available symbolic re…
Quantifying effects of inhomogeneities and curvature on gravitational wave standard siren measurements of
S. M. Koksbang
For a flat CDM universe, the dipole of the luminosity distance can be utilized to measure the Hubble parameter. It is here shown that this is not the case in more general settin…
Redshift drift in a universe with structure I: Lemaitre-Tolman-Bondi structures with arbitrary angle of entry of light
Sofie Marie Koksbang, Asta Heinesen
We consider the redshift drift and position drift associated with astrophysical sources in a formalism that is suitable for describing emitters and observers of light in an arbitra…
The effect of dark matter discreteness on light propagation
Sofie Marie Koksbang, Syksy Rasanen
Light propagation in cosmology is usually studied in the geometrical optics approximation which requires the spacetime curvature to be much smaller than the light wavenumber. Howev…
Understanding the Dyer-Roeder approximation as a consequence of local cancellations of projected shear and expansion rate fluctuations
S. M. Koksbang
It is shown with several concrete examples that the Dyer-Roeder approximation is valid in spacetimes which fulfill the condition that fluctuations in the expansion rate along a lig…
Searching for signals of inhomogeneity using multiple probes of the cosmic expansion rate H(z)
S. M. Koksbang
It is argued that cosmic chronometers yield estimates of the spatially averaged expansion rate even in a universe that is not well described by a global FLRW model - as long as the…
On the relationship between mean observations, spatial averages and the Dyer-Roeder approximation in Einstein-Straus models
S. M. Koksbang
The redshift and redshift-distance relation in different Einstein-Straus models are considered. Specifically, the mean of these observables along 1000 light rays in different speci…