Gravitational transitions via the explicitly broken symmetron screening mechanism

Understand

We generalize the symmetron screening mechanism by allowing for an explicit symmetry breaking of the symmetron $\phi^4$ potential.

• A coupling to matter of the form $A(\phi)=1+\frac{\phi^2}{M^2}$ leads to an explicitly broken symmetry with effective potential $V_{eff}(\phi)=-\mu^2 (1-\frac{\rho}{\mu^2 M^2})\phi^2 +\frac{\lambda}{2}\phi^4 + 2 \varepsilon \phi^3+\frac{\lambda}{2}\eta^4$.
• Due to the explicit symmetry breaking induced by the cubic term we call this field the 'asymmetron'.
• For large matter density $\rho>\rho_*\equiv \mu^2M^2+\frac{9}{4}\varepsilon\eta M^2$ the effective potential has a single minimum at $\phi=0$ leading to restoration of General Relativity as in the usual symmetron screening mechanism.