The bipolar filtration introduced by T Cochran, S Harvey and P Horn
is a framework for the study of smooth concordance of topologically
slice knots and links. It is known that there are topologically slice
–bipolar knots which
are not
–bipolar.
For knots, this is the highest known level at which the filtration does
not stabilize. For the case of links with two or more components,
we prove that the filtration does not stabilize at any level: for any
, there are topologically slice
links which are
–bipolar
but not
–bipolar.
In the proof we describe an explicit geometric construction which raises the bipolar
height of certain links exactly by one. We show this using the covering link
calculus. Furthermore we discover that the bipolar filtration of the group of
topologically slice string links modulo smooth concordance has a rich algebraic
structure.
Keywords
covering link calculus, concordance, bipolar filtration
Department of Mathematics
Pohang University of Science and Technology
Gyungbuk
Pohang 790-784
South Korea
and
School of Mathematics
Korea Institute for Advanced Study
Seoul 130–722
South Korea