White dwarfs as a probe of dark energy
  We investigate the radial density distribution of the dynamical dark energy
inside the white dwarfs (WDs) and its possible impact on their intrinsic
structure. The minimally-coupled dark energy with barotropic equation of state
which has three free parameters (density, equation of state and effective sound
speed) is used. We analyse how such dark energy affects the mass-radius
relation for the WDs because of its contribution to the joint gravitational
potential of the system. For this we use Chandrasekhar model of the WDs, where
model parameters are the parameter of the chemical composition and the
relativistic parameter. To evaluate the dark energy distribution inside a WD we
solve the conservation equation in the spherical static metric. Obtained
distribution is used to find the parameters of dark energy for which the
deviation from the Chandrasekhar model mass-radius relation become
non-negligible. We conclude also, that the absence of observational evidence
for existence of WDs with untypical intrinsic structure (mass-radius relation)
gives us lower limit for the value of effective sound speed of dark energy
$c_s^2 \gtrsim 10^{-4}$ (in units of speed of light).
