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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…
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…
Kinetic field theory: effects of modified gravity theories with screening mechanisms on non-linear cosmic density fluctuations
Alexander Oestreicher, Harshda Saxena, Niklas Reinhardt +3
In a mean-field approximation within Kinetic Field Theory, it is possible to derive an accurate analytic expression for the power spectrum of present-day non-linear cosmic density…
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…
Kinetic field theory: generic effects of alternative gravity theories on non-linear cosmic density-fluctuations
Alexander Oestreicher, Lodovico Capuano, Sabino Matarrese +2
Non-linear cosmic structures contain valuable information on the expansion history of the background space-time, the nature of dark matter, and the gravitational interaction. The r…