  A promising extension of general relativity is Chern-Simons (CS) modified
gravity, in which the Einstein-Hilbert action is modified by adding a
parity-violating CS term, which couples to gravity via a scalar field. In this
work, we consider the interesting, yet relatively unexplored, dynamical
formulation of CS modified gravity, where the CS coupling field is treated as a
dynamical field, endowed with its own stress-energy tensor and evolution
equation. We consider the possibility of observationally testing dynamical CS
modified gravity by using the accretion disk properties around slowly-rotating
black holes. The energy flux, temperature distribution, the emission spectrum
as well as the energy conversion efficiency are obtained, and compared to the
standard general relativistic Kerr solution. It is shown that the Kerr black
hole provide a more efficient engine for the transformation of the energy of
the accreting mass into radiation than their slowly-rotating counterparts in CS
modified gravity. Specific signatures appear in the electromagnetic spectrum,
thus leading to the possibility of directly testing CS modified gravity by
using astrophysical observations of the emission spectra from accretion disks.
