Dark-energy properties of a spacetime-symmetry breaking cosmological solution -- late-time behaviour and phantom crossing
We investigate the late-time cosmological dynamics in a simple case of explicit spacetime-symmetry breaking. By expanding in a small symmetry-breaking coefficient we are able to write the Friedmann equations as $\Lambda$CDM + dynamical dark energy, which we show contains logarithmic dependence of the scale factor. We find that the dark energy equation of state displays divergences and phantom behaviour for certain values of the symmetry-breaking coefficient, where the Null Energy Condition is also broken. We also discuss the adiabatic sound speed of dark energy and compare the model to current constraints using the Chevallier-Polarski-Linder parametrisation.