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arXiv · 2608.10552

Two-Fluid Schwarzschild Solution

Rico Zöllner·Burkhard Kämpfer
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Abstract

We consider the interior two-fluid Schwarzschild solution. That is a model of compact (neutron) stars with admixed dark matter. The two constant energy densities generalize the interior Schwarschild solution to the case of two fluids (representing standard model matter and dark matter, for instance), interacting mutually solely by the common gravitational field. In general, the two-fluid core is surrounded by a one-fluid corona (envelope). Only for special parameters (the model depends on energy densities $e_1,e_2$ and central pressures $p_{\mathrm{c}1},p_{\mathrm{c}2}$ of the fluids), both fluids occupy the same region. Despite the sum of two energy densities in that region, the compactness bound of 8/9 is not exceeded. A conceivable object is one with a stark leakage of one fluid (e.g. dark matter) beyond the two-fluid core.

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Rico Zöllner, Burkhard Kämpfer. 2026-08-11. Two-Fluid Schwarzschild Solution. https://arxiv.org/abs/2608.10552

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