Title: $A_\infty$ obstruction theory and the strict associativity of $E/I$

Author: Vigleik Angeltveit

E-mail address: vigleik@math.mit.edu

Address: Department of Mathematics, Massachusetts Institute of Technology,
Cambridge, Massachusetts 02139, USA

Abstract: We prove that for a ring spectrum $K$ with a perfect universal 
coefficient formula, the obstructions to extending the multiplication 
to an $A_\infty$ multiplication lie in $Ext^{*,*}_{K_*K^{op}}(K_*,K_*)$.
As a corollary, we show that if $E$ is even and $I=(x_1,x_2,\ldots)$ is
a regular sequence in $E_*$, then any product on $E/I$ can be extended
to an $A_\infty$ multiplication.