  We obtain the equation of state (EoS) and the sound velocity for 2-color QCD
at low temperature and high density and find that in the superfluid phase,
$c_s^2/c^2 >1/3$, where $1/3$ is the value at the relativistic limit. Several
independent Monte Carlo studies on 2-color QCD have been conducted intensively
in recent years. These works have shown a clear evidence of phase transition
between hadronic and superfluid phases. In our paper[1], we have investigated
the EoS and sound velocity in both phases. Our result is consistent with chiral
perturbation theory in a low $\mu$ regime of the superfluid phase including the
Bose-Einstein condensed phase, and shows a peak of sound velocity in the
high-density BCS phase. We also give detailed simulation results and a comment
on the holography bound in this proceedings.
