Let F : M ×In → Q×In be an
n-isotopy (not necessarily PL) of a compact PL m-manifold M in a PL q-manifold Q,
and let G : Q × In → Q × In be an ambient isotopy of Q which covers F on
Q × ∂In. If m ≦ q − 3 there is in πn PL(M,Q) an obstruction to finding an
ambient isotopy of Q, isotopic to G, which covers F and agrees with G on
Q × ∂In.
|