Evading the astrophysical limits on light pseudoscalars

TL;DR

The paper examines whether astrophysical bounds on light pseudoscalars can be evaded if the pseudoscalar has a sizable self-coupling. It argues that strong $\\phi^4$ self-interaction drives trapping and rapid fragmentation inside the Sun, creating a dense, nonrelativistic pseudoscalar population with an effectively negligible radiative transport contribution, thereby reconciling PVLAS-allowed parameters with bounds. A gravitationally bound pseudoscalar halo can extend beyond the solar radius, and for many parameter choices the standard bounds no longer apply. The work suggests a possible link between these light states and dark matter and highlights the importance of self-interactions in shaping astrophysical constraints.

Abstract

We study the possibility of evading astrophysical bounds on light pseudoscalars. We argue that the solar bounds can be evaded if we have a sufficiently strong self coupling of the pseudoscalars. The required couplings do not conflict with any known experimental bounds. We show that it is possible to find a coupling range such that the results of the recent PVLAS experiment are not in conflict with any astrophysical bounds.

Figures (5)

• Figure 1: Feynman diagram for the Primakoff process for the conversion of photons $\gamma(k)$ into pseudoscalars $\phi(k')$.
• Figure 2: The process $\phi\phi\rightarrow \phi\phi\phi\phi$ through a loop diagram.
• Figure 3: Feynman diagram for the inverse Primakoff process for the conversion of pseudoscalars $\phi(k)$ to photons $\gamma(k')$.
• Figure 4: Some of the diagrams which contribute to energy loss of pseudoscalars as they propagate through sun. Here the pseudoscalar, electron and photon are represented by dashed, solid and wavy lines respectively.
• Figure 5: The mass contribution of pseudoscalars, $M_r$, as a function of the distance from the center of the sun.