Varying alpha from N-body Simulations

Understand

We have studied the Bekenstein-Sandvik-Barrow-Magueijo (BSBM) model for the spatial and temporal variations of the fine structure constant, alpha, with the aid of full N-body simulations which explicitly and self-consistently solve for the scalar field driving the alpha-evolution.

• We focus on the scalar field (or equivalently alpha) inside the dark matter halos and find that the profile of the scalar field is essentially independent of the BSBM model parameter.
• This means that given the density profile of an isolated halo and the background value of the scalar field, we can accurately determine the scalar field perturbation in that halo.
• We also derive an analytic expression for the scalar-field perturbation using the Navarro-Frenk-White halo profile, and show that it agrees well with numerical results, at least for isolated halos; for non-isolated halos this prediction differs from numerical result by a (nearly) constant offset which depends on the environment of the halo.