Dark Matter in White Dwarfs: Implications for Their Structure

Abstract: White Dwarfs (WDs), the final evolutionary stage of most stars, are frequently modeled considering only a dense plasma matter. However, their potential interaction with dark matter (DM), especially in galactic halos where DM is expected to be prevalent, may lead to significant consequences. This work proposes a novel EoS (EoS) that consistently incorporates both hot dense plasma and cold dark matter (CDM) contributions in hot WDs. The hot dense plasma EoS is extended to include thermal and radiative contributions. At the same time, the CDM component is modeled as a linear fluid, with the coupling constant $\alpha$ determined self-consistently within the star. A smooth phase transition between hot dense plasma and CDM regimes is introduced via a hyperbolic mixing function that depends on local energy density and stellar temperature. Our results show that the inclusion of CDM leads to an increase in the WD radius by approximately $12\%$ and a total mass enhancement of $0.7\%$, compared to standard hot WD models without lattice effects. These results highlight the importance of considering CDM in stellar modeling and suggest that WDs may serve as indirect probes for the astrophysical properties of dark matter.