Heisenberg groups and algebraic topology
by Jack Morava
	
This paper overlaps considerably with earlier, sketchier papers 
about the Tate cohomology of circle actions and its connection
to Heisenberg groups. It will appear in the Segal Festschrift:

We study the Madsen-Tillmann spectrum $\C P^\infty_{-1}$ as a quotient 
of the Mahowald pro-object $\C P^{\infty}_{-\infty}$, which is closely 
related to the Tate cohomology of circle actions. That theory has an
associated symplectic structure, whose symmetries define the Virasoro 
operations on the cohomology of moduli space constructed by Kontsevich 
and Witten.