  Solid He-4 is viewed as a nearly perfect Debye solid. Yet, recent calorimetry
measurements by the PSU group (J. Low Temp. Phys. 138, 853 (2005) and Nature
449, 1025 (2007)) indicate that at low temperatures the specific heat has both
cubic and linear contributions. These features appear in the same temperature
range where measurements of the torsional oscillator period suggest a
supersolid transition. We analyze the specific heat and compare the measured
with the estimated entropy for a proposed supersolid transition with 1%
superfluid fraction and find that the observed entropy is too small. We suggest
that the low-temperature linear term in the specific heat is due to a glassy
state that develops at low temperatures and is caused by a distribution of
tunneling systems in the crystal. We propose that dislocation related defects
produce those tunneling systems. Further, we argue that the reported putative
mass decoupling, that means an increase in the oscillator frequency, is
consistent with a glass-like transition. The glass scenario offers an
alternative interpretation of the torsional oscillator experiments in contrast
to the supersolid scenario of nonclassical rotational inertia.
