  We suggest that below a certain temperature T_k, the free energy for the
creation of kinks-antikinks pairs in the dislocation network of solid He4
becomes negative. The underlying physical mechanism is the related liberation
of vacancies which initiate Feynman's permutation cycles in the bulk.
Consequently, dislocations should wander and sweep an increasingly larger
volume at low temperatures. This phenomenon should lead both to a stiffening of
the solid below T_k and to the appearance of a non zero superfluid fraction at
a second temperature T_c < T_k.

Statistical Mechanics