  A knot in a thickened surface $K$ is a smooth embedding $K:S^1 \rightarrow
\Sigma \times [0,1]$, where $\Sigma$ is a closed, connected, orientable
surface. There is a bijective correspondence between knots in $S^2 \times
[0,1]$ and knots in $S^3$, so one can view the study of knots in thickened
surfaces as an extension of classical knot theory. An immediate question is if
other classical definitions, concepts, and results extend or generalize to the
study of knots in a thickened surface. One such famous result is the Fox Milnor
Theorem, which relates the Alexander polynomials of concordant knots. We prove
a Fox Milnor Theorem for concordant knots in a thickened surface by using
Milnor torsion.
