http://arxiv.org/abs/1707.01053
Building upon the recently developed formalism of Kinetic Field Theory (KFT) for cosmic structure formation by Bartelmann et al., we investigate the effects of particle diffusion on the formation of structure in the Universe in the context of fluctuation-dissipation relations (FDRs). In our earlier analysis we observed that diffusion damps the growth of structures on small scales in the free theory. However, artificially removing some part of diffusion leads to remarkably good agreement with N-body simulations. The goal of this work is to achieve a better understanding of diffusion in KFT and the success of the approximative removal of diffusion. In the first part of this work we examine the time derivative of density correlations in the free theory and observe that structure formation on this level is a detailed balance between particle diffusion on the one side and the accumulation of structure due to initial momentum correlations on the other side. In the second part, we show that the response of the system to two-particle interactions is directly related to the evolution of particle diffusion in the form of FDRs. This demonstrates how interactions decrease diffusion and motivates the artificial removal of diffusion. Furthermore, we show that the FDRs are connected to a time-reversal symmetry of the underlying generating functional as is typical for statistical field theories.
J. Dombrowski, F. Fabis and M. Bartelmann
Wed, 5 Jul 17
32/60
Comments: 28 pages, 6 figures, submitted to New Journal of Physics
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