  In models in which some of the scalar field are charged and some uncharged,
interactions with a finite temperature plasma will lead to corrections to the
effective potential of the charged fields which may stabilize embedded defects
made up of uncharged fields. In these models embedded defects, solutions of the
field equations which are unstable at zero temperature, may thus be stable in
the early Universe, and may then play an important role in cosmology. Two
prototypical examples are the pion string in the theory of strong interactions,
and the electroweak Z-string in the standard electroweak theory.
