Scalars Gliding Through an Expanding Universe
  In this article we investigate the effects of single derivative mixing in
massive bosonic fields. In the regime of large mixing, we show that this leads
to striking changes of the field dynamics, delaying the onset of classical
oscillations and decreasing, or even eliminating, the friction due to Hubble
expansion. We highlight this phenomenon with a few examples. In the first
example, we show how an axion like particle can have its number abundance
parametrically enhanced. In the second example, we demonstrate that the QCD
axion can have its number abundance enhanced allowing for misalignment driven
axion dark matter all the way down to $f_a$ of order astrophysical bounds. In
the third example, we show that the delayed oscillation of the scalar field can
also sustain a period of inflation. In the last example, we present a situation
where an oscillating scalar field is completely frictionless and does not
dilute away in time.
