Kinematics of the Galaxy from Young Open Star Clusters with Data from
  the Gaia EDR3 Catalogue
  We have analyzed the kinematics of open star clusters (OSCs) with the proper
motions and distances calculated by Hao et al. based on Gaia EDR3 data. The
mean line-of-sight velocities are known for a number of clusters from this
list. We show that the Galactic rotation parameters determined from samples of
OSCs with various ages are in good agreement between themselves. The most
interesting results have been obtained from a sample of 967 youngest OSCs with
a mean age of 18 Myr. In particular, we have found the following parameters of
the angular velocity of Galactic rotation using only their proper motions and
distances:
  $\Omega_0 =28.01\pm0.15$ km s$^{-1}$ kpc$^{-1},$
  $\Omega^{'}_0=-3.674\pm0.040$ km s$^{-1}$ kpc$^{-2},$ and
  $\Omega^{''}_0=0.565\pm0.023$ km s$^{-1}$ kpc$^{-3}$. The circular rotation
velocity of the solar neighborhood around the Galactic center here is
$V_0=226.9\pm3.1$ km s$^{-1}$ for the adopted Galactocentric distance of the
Sun $R_0=8.1\pm0.1$ kpc. The parameters of the spiral density wave have been
determined from the space velocities of 233 young clusters. The amplitudes of
the radial and tangential velocity perturbations produced by the spiral density
wave are $f_R=9.1\pm0.8$ km s$^{-1}$ and $f_\theta=4.6\pm1.2$ km s$^{-1}$,
respectively; the perturbation wavelengths are $\lambda_R=3.3\pm0.5$ kpc and
$\lambda_\theta=2.6\pm0.6$ kpc for the the adopted four-armed spiral pattern.
The Sun's phase in the spiral density wave has been found to be
$(\chi_\odot)_R\approx-180^\circ$.
