The QCD nature of Dark Energy

Understand

The origin of the observed dark energy could be explained entirely within the standard model, with no new fields required.

• We show how the low-energy sector of the chiral QCD Lagrangian, once embedded in a non-trivial spacetime, gives rise to a cosmological vacuum energy density which can be can be presented entirely in terms of QCD parameters and the Hubble constant $H$ as $\rho_\Lambda \simeq H \cdot m_q\la\bar{q}q\ra /m_{\eta'} \sim (4.3\cdot 10^{-3} \text{eV})^4$.
• In this work we focus on the dynamics of the ghost fields that are essential ingredients of the aforementioned Lagrangian.
• In particular, we argue that the Veneziano ghost, being unphysical in the usual Minkowski QFT, becomes a physical degree of freedom if the universe is expanding.