One hundred and fifth meeting of the
University of Sheffield
Wednesday 24th January 2018
morning talk will be in Lecture Theatre 5 on floor E of the Hicks
Building. The afternoon talks will be in J11 (J floor) and coffee/tea
in the common room I15 (I floor) of the Hicks building.
11:00 - 11:30
common room I15
|11:30 - 12:30|
|Will Rushworth (Durham)|
Doubled Khovanov homology
|12:30 - 14:00||Lunch|
|14:00 - 15:00|
|Jocelyne Ishak (Kent)|
Rigidity of the K(1)-local stable homotopy category
|15:00 - 16:00|
common room I15
|16:00 - 17:00|
|Richard Webb (Cambridge)|
The conjugacy problem for the mapping class group in polynomial time
A group is expected to go for drinks and an early dinner after the last talk. Everyone is welcome to join us.
Abstracts of talks
Jocelyne Ishak (Kent)
Title: Rigidity of the K(1)-local stable homotopy category.
some cases, it is sufficient to work in the homotopy category Ho(C)
associated to a model category C, but looking at the homotopy level
alone does not provide us with higher order structure information.
Therefore, we investigate the question of rigidity: If we
just had the structure of the homotopy category, how much of the
underlying model structure can we recover? For example, the stable
homotopy category Ho(Sp) has been proved to berigid by S.
Schwede. Moreover, the E(1)-local stable homotopy category, for
p=2, has been shown to be rigid by C. Roitzheim.
this talk, I will discuss a new case of rigidity, which is
the localization of spectra with respect to the Morava
K-theory K(1), at p=2. While the K(n)-local spectra can
be related to the E(n)-local spectra, there are a lot of main
differences to keep in mind while studying the rigidity in
the K(1)-local case. Therefore, what might be true and applicable
for the E(1)-localization studied by C.Roitzheim might not be true
anymore in the K(1)-local world. In this talk, I will emphasis those
differences, and sketch the proof of the rigidity of the
K(1)-local stable homotopy category at p=2.
Will Rushworth (Durham)
Title: Doubled Khovanov homology
knot theory is an extension of classical knot theory which considers
knots and links in equivalence classes of thickened orientable surfaces. Khovanov
homology is a powerful invariant of classical links, and it can be
applied to virtual links using Z_2 coefficients. However, a number of
problems arise when one attempts to use other coefficient rings. In
this talk we describe doubled Khovanov homology: an extension of
Khovanov homology to virtual links with arbitrary coefficients. Unlike
other extensions of Khovanov homology, doubled Khovanov homology
requires no new diagrammatics, as all the work is done algebraically.
We shall describe the construction of the invariant as well as some of
its applications, in particular to virtual knot concordance.
Richard Webb (Cambridge)
Title: The conjugacy problem for the mapping class group in polynomial time
an orientable surface S of finite type. We shall describe an algorithm
that solves the conjugacy problem in the mapping class group of S in
polynomial time. This includes closed surfaces S and the braid groups.
Joint work with Mark Bell.
Everyone who wishes to participate is welcome, particularly
postgraduate students. The usual criteria for
assistance with travel expenses apply. Beneficiaries will need to
complete the standard forms, which are available at the