Tachyonic quintessence and a preferred direction in the sky

We show that quintessence, when it is described by a tachyonic field, can amplify a tiny primordial gradient generating a preferred direction in the sky. In its simplest realization, this mechanism only affects the cosmic microwave background fluctuations at the quadrupole level. We briefly discuss how higher multipoles can also be affected, once the full structure of the quintessence potential is taken into account.

Figure 1

The quantity $|\delta b_0({\eta }_0)-\delta a_0({\eta }_0)|/{\overline{\kappa }}_1^2$ plotted as a function of $\mu$.