Cosmological consequences of a scalar field with oscillating equation of
  state: A possible solution to the fine-tuning and coincidence problems
  We propose a new dark energy model for solving the cosmological fine-tuning
and coincidence problems. A default assumption is that the fine-tuning problem
disappears if we do not interpret dark energy as vacuum energy. The key idea to
solving the coincidence problem is that the Universe may have several
acceleration phases across the whole cosmic history. The specific example we
study is a quintessence model with approximately repeated double exponential
potential, which only introduces one Planck scale parameter and three
dimensionless parameters of order unity. The cosmological background evolution
equations can be recast into a four-dimensional dynamical system and its main
properties are discussed in details. Preliminary calculations show that our
model is able to explain the observed cosmic late-time acceleration.
