Astrophysical Configurations with Background Cosmology: Probing Dark Energy at Astrophysical Scales

TL;DR

This paper investigates how a positive cosmological constant influences the structure and stability of astrophysical objects modeled by polytropic equations, revealing constraints and features that could serve as independent probes of dark energy.

Contribution

It derives conditions for equilibrium and stability of astrophysical configurations with dark energy, highlighting the impact on models like isothermal spheres and exotic objects.

Findings

Isothermal sphere models are not viable with a positive cosmological constant.

Central density must exceed a minimal value related to vacuum density for finite configurations.

Dark energy influences properties of neutrino and boson stars, offering potential observational probes.

Abstract

We explore the effects of a positive cosmological constant on astrophysical and cosmological configurations described by a polytropic equation of state. We derive the conditions for equilibrium and stability of such configurations and consider some astrophysical examples where our analysis may be relevant. We show that in the presence of the cosmological constant the isothermal sphere is not a viable astrophysical model since the density in this model does not go asymptotically to zero. The cosmological constant implies that, for polytropic index smaller than five, the central density has to exceed a certain minimal value in terms of the vacuum density in order to guarantee the existence of a finite size object. We examine such configurations together with effects of $\Lambda$ in other exotic possibilities, such as neutrino and boson stars, and we compare our results to N-body simulations. The astrophysical properties and configurations found in this article are specific features resulting from the existence of a dark energy component. Hence, if found in nature would be an independent probe of a cosmological constant, complementary to other observations.