k-Mouflage gravity

Abstract

We introduce a large class of scalar-tensor theories where gravity becomes stronger at large distances via the exchange of a scalar that mixes with the graviton. At small distances, i.e. large curvature, the scalar is screened via an analog of the Vainshtein mechanism of massive gravity. The crossover distance between the two regimes can be made cosmological by an appropriate choice of the parameters.

Figures (1)

• Figure 1: Left figure shows the derivative of the scalar field, $\phi'$, in the presence of a source of radius $R= 0.01$ (in the unit of the Vainshtein radii of the models) for $H \equiv H_K(X) \propto X^2$ (dashed blue curve), and $H=H_{DGP}$ (red solid line). The different asymptotic regimes are shown by thin lines. One sees in particular the transition happening at the Vainshtein radii $R_{V,H}$. The right plot shows the derivative of the functions $\lambda$ and $\nu$, $\lambda'$ (dashed blue curve) and $\nu'$ (red solid curve), appearing in the spherically symmetric ansatz (\ref{['ANG']}), along with $\phi'$ (thin black curve), for the $H \equiv H_K(X) \propto X^2$ model and outside the source. One sees the transition between GR regime ($R \ll R_{V,H}$) and the scalar-tensor regime ($R \gg R_{V,H}$). Below $R_{V,H}$ the scalar field "camouflages", i.e. its contribution becomes subdominant.