Cosmic Steps in Modeling Dark Energy
  The past and recent data analyses gave some hints of steps in dark energy.
Considering the dark energy as a dynamical scalar field, we investigate several
models with various steps: a step in the scalar potential, a step in the
kinetic term, a step in the energy density and a step in the equation-of-state
parameter w. These toy models provide a workable mechanism to generate steps
and features of dark energy. Remarkably, a single real scalar can cross w=-1
dynamically with a step in the kinetic term.
