Interpretation of relativistic effects and corrections within cosmological structure formation

• Applicant: Dr. Cornelius Stefan Rampf
• Subject Area: Astrophysics and Astronomy ; Mathematics
• Term: from 2013 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 248747090

According to the standard model of cosmology the large-scale structure (i.e., clusters of galaxies) of the universe is largely the result of gravitational instability. By studying the gravitational evolution with analytical and numerical methods we can verify the theory of gravitation, but we are also able to shed light into the energy composition of our universe. The latter also means to understand the mysterious nature of the yet undiscovered dark matter and dark energy.So far all measured effects on cosmological scales (1 Mpc - 100 Mpc) are only constrained up to leading order within general relativity. Putting aside purely relativistic effects (e.g., the gravitational lensing), relativistic corrections usually enter beyond leading order, i.e., such corrections are small with respect to the Newtonian bulk part. Current and forthcoming large-scale surveys (such as SDSS or ESA's Euclid satellite) will resolve the large-scale structure to unprecedented accuracy, and reduce uncertainties within the cosmological model to the per cent level. Thus, it is crucial to constrain effects and corrections coming from general relativity to sufficient accuracy.Identifying relativistic effects within cosmological structure formation is one of the objectives in the proposed project. Most importantly, the aim of this project is to concentrate on the fundamental role of the observer in relativistic structure formation. We shall investigate how relativistic effects affect the interpretation of observations, which is a non-trivial issue in general relativity. This becomes increasingly important when we interpret survey data-especially considering that cosmology has moved into being a precision science.Additionally, my part of the project is to apply the findings to a relativistic interpretation of numerical simulations. These simulations use the Newtonian approximation because a fully relativistic treatment is not feasible. The essential objective is to deliver a direct connection between Newtonian simulations and general relativity, i.e., whether the particle's positions have to be updated/displaced according to the relativistic constraints, and/or whether the volume of the grid cells in the numerical simulation is deformed. The key analytic technique for these (and the following) considerations is the Lagrangian perturbation theory, in which I have gained expertise in my years of research.I will also proceed with my current efforts in embedding relativistic corrections in terms of the initial conditions of such numerical simulations. Successful considerations could then establish simple and computationally fast quasi-relativistic simulations.

• DFG Programme: Research Fellowships
• International Connection: United Kingdom
• Host: Professor Dr. David Wands