  I present two interesting studies related to the role of solitons in theories
with spontaneous symmetry breaking. Quantised fermions coupled to solitons are
known to induce fractional fermion number. I present an example where an
unstable topological solution binding a zero mode of a majorana fermion gets
stabilised due to the induced fractional number. Thus neither is the cosmic
string stable nor is the fermion number conserved, yet the bound state then
becomes stable due to Quantum Mechanics. The other phenomenon concerns a
metastable vacuum getting destabilised due to the presence of a cosmic string.
This happens because the scalar field signalling spontaneous symmetry breaking
acquires a vacuum expectation value approaching its true vacuum value in the
core of the string. Thus the string acts like a seed nucleating the true
vacuum. The instanton mediating between the false vacuum and the exit point
into the true vacuum is shown to exist and graphically displayed through a
numeric calculation. T. Padmanabhan has been a long time friend and was
collaborator for early investigations in this direction. I review these works
done subsequently with other collaborators as a felicitation to him on his
sixtieth birthday.
