Dislocations are shown to be smooth at zero temperature because of the effective Coulomb-type interaction between kinks. Crossover to finite temperature rougnehing is suggested to be a mechanism responsible for the softening of \he4 shear modulus recently observed by Day and Beamish (Nature, {\bf 450}, 853 (2007)). We discuss also that strong suppresion of superfuidity along the dislocation core by thermal kinks can lead to locking in of the mechanical and superfluid responses.
@article{arxiv.0812.0983,
title = {Mechanical and superfluid properties of dislocations in solid He4},
author = {D. Aleinikava and E. Dedits and A. B. Kuklov and D. Schmeltzer},
journal= {arXiv preprint arXiv:0812.0983},
year = {2008}
}