Dark energy from a renormalization group flow

We present evidence that a special class of gravitationally coupled hidden sectors, in which conformal invariance is dynamically broken in a controlled way, exhibit the properties of dark energy. Such quantum field theories may appear while embedding the standard model in a more fundamental high energy theory. At late times, an effective dark energy field behaves similarly to an exponentially small cosmological constant while at early times its energy density partly tracks that of matter.

Figure 1

Numerical solutions for $\zeta$, the scale factor $a$, the Hubble parameter $H$, and the equation of state $w$.

Figure 2

The energy density of the $\zeta$ fluid (flattening out at nonzero $\rho (t)$ and matter (flattening out at vanishing $\rho (t)$ as a function of time. At early times, the two curves are essentially parallel, showing that the $\zeta$ energy density tracks the matter energy density. Despite the oscillatory behavior of $\zeta$, the energy densities are monotonic functions.