The effective field theory of multi-component fluids
- Institut für Theoretische Physik, Universität Heidelberg, Philosophenweg 16, D-69120 Heidelberg (Germany)
- Institut de Physique Théorique, CEA-Saclay and CNRS URA-2306, F-91191 Gif-sur-Yvette Cedex (France)
- Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States)
We study the effective Lagrangian, at leading order in derivatives, that describes the propagation of density and metric fluctuations in a fluid composed by an arbitrary number of interacting components. Our results can be applied to any situation in cosmology where different species have non-gravitational interactions. In time-dependent backgrounds, such as FLRW, the quadratic action can only be diagonalized at fixed time slices and flavour mixing is unavoidable as time flows. In spite of this, the fluid can be interpreted at the level of the linear equations of motion as an ensemble of individual interacting species. We show that interactions lead to anisotropic stresses that depend on the mixing terms in the quadratic action for perturbations. In addition to the standard entrainment among different components, we find a new operator in the effective action that behaves as a cosmological constant when it dominates the dynamics.
- OSTI ID:
- 22373606
- Journal Information:
- Journal of Cosmology and Astroparticle Physics, Vol. 2014, Issue 05; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 1475-7516
- Country of Publication:
- United States
- Language:
- English
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