Effect of the cosmological constant on halo size

Abstract

In this work, we consider the effect of the cosmological constant on galactic halo size. As a model, we study the general relativistic derivation of orbits in the Schwarzschild-de Sitter metric. We find that there exists a length scale rΛ corresponding to a maximum size of a circular orbit of a test mass in a gravitationally bound system, which is the geometric mean of the cosmological horizon size squared, and the Schwarzschild radius. This agrees well with the size of a galactic halo when the effects of dark matter are included. The size of larger structures such as galactic clusters and superclusters are also well-approximated by this scale. This model provides a simplified approach to computing the size of such structures without the usual detailed dynamical models. Some of the more detailed approaches that appear in the literature are reviewed, and we find the length scales agree to within a factor of order one. Finally, we note the length scale associated with the effects of MOND or Verlinde's emergent gravity, which offer explanations of the flattening of galaxy rotation curves without invoking dark matter, may be expressed as the geometric mean of the cosmological horizon size and the Schwarzschild radius, which is typically 100 times smaller than rΛ.

Linear Potentials in Galaxy Halos by Asymmetric Wormholes

“…Other theorists instead have tried to modify General Relativity (GR) or the Newtonian laws. The most prevailing belief is that for explaining the galaxy rotation curves, the galaxy has to be soaked in a dark matter halo [1][2][3]. Regardless of this question, a theoretical spherically symmetric solution for GR, called a wormhole, where two different universes can be causally connected through a "wormhole throat" and where a physical traveller can go in principle from one universe to the other and be observed doing this from an observer located in one of the universes, gives a concept of a non-trivial topological structure linking separate points in space-time [4][5][6][7].…”