Self Interacting Dark Matter in the Solar System

TL;DR

The paper addresses reconciling PVLAS-like hints of a light pseudoscalar with astrophysical bounds by invoking a self-interacting, weakly coupled pseudoscalar that forms a subdominant component of galactic dark matter. The authors propose that a perturbative self-coupling $\alpha_\lambda = \lambda^2 / 4\pi \le 0.1$ causes rapid pseudoscalar fragmentation inside stars, trapping the particles and suppressing energy transport, while a galactic density $n_φ$ (scaled by factors $ξ$) provides a reservoir in the Sun's vicinity. They analyze two limiting density/thermal scenarios: thermal equilibrium inside the Sun and a fragmentation-dominated regime outside, both yielding pseudoscalar densities and mean free paths that keep energy transport dominated by photons and preserve Solar Model energy balance. Medium corrections to the pseudoscalar mass via $\delta m_{\rm th}^2$ remain small for $T \lesssim m_φ$ and $\lambda < 1$, ensuring compatibility with PVLAS interpretations. Overall, the study shows a viable pathway to evade solar bounds on pseudoscalar–photon couplings while maintaining consistency with laboratory signals, given a perturbative self-interaction and a subdominant galactic density.

Abstract

Weakly coupled, almost massless, spin 0 particles have been predicted by many extensions of the standard model of particle physics. Recently, the PVLAS group observed a rotation of polarization of electromagnetic waves in vacuum in the presence of transverse magnetic field. This phenomenon is best explained by the existence of a weakly coupled light pseudoscalar particle. However, the coupling required by this experiment is much larger than the conventional astrophysical limits. Here we consider a hypothetical self-interacting pseudoscalar particle which couples weakly with visible matter. Assuming that these pseudoscalars pervade the galaxy, we show that the solar limits on the pseudoscalar-photon coupling can be evaded.

Figures (2)

• Figure 1: Feynman diagram for the fragmentation process $\phi \phi \rightarrow \phi \phi \phi\phi$.
• Figure 2: Density Profile of Pseudoscalars With Distance.