Cosmic birefringence and electroweak axion dark energy

Taking the recently reported non-zero rotation angle of cosmic microwave background (CMB) linear polarization $\beta=0.35\pm0.14{\rm\, deg}$ as hint for a pseudo Nambu-Goldstone boson quintessence dark energy (DE), we study electroweak (EW) axion DE model where mass is generated by EW instantons. We find that observed value $\beta$ implies non-trivial $U(1)$ electromagnetic anomaly coefficient ($c_{\gamma}$), once current constraint on equation state also taken into account. With aid hypothetical high structure inspired experimentally inferred $c_{\gamma}$, shown to be able make prediction ($w_{\rm DE,0}$) DE. This expected our scenario distinguishable in comparison with cosmological constant ($w=-1$) and testable future when error measurement $w_{\rm DE,0}$ reduced $\mathcal{O}(1)\%$ level ($\delta w=\mathcal{O}(10^{-2})$).