New postdoc job postings at Warwick

Saul Schleimer has asked me to point out two job ads for postdocs at Warwick that are still open.  The deadline is soon – July 7th, and Saul is hoping some topologists will apply.  They’re two year positions with light teaching loads.  Here are the links:

http://www2.warwick.ac.uk/fac/sci/maths/jobs
https://secure.admin.warwick.ac.uk/webjobs/jobs/academic/job26360.html

Frohman’s Trick

Here’s a neat trick that Charles Frohman related to me a number of years ago.  I think it’s in this paper [1], though I wasn’t able to find it in there.  The trick is beautifully simple, but there don’t seem to be that many applications of it.  In fact, as far as I know the only application is in Frohman’s paper. Here’s the Lemma:  Let be a Heegaard surface in a 3-manifold (other than the 3-sphere) and assume there is aball such that the intersection of and is not planar.  Then is reducible.  (Recall that a Heegaard surface is reducible if there is a sphere that intersects it in a single essential loop.)