fix rigidity condition

Author: ecpeterson

sigma.tex

@@ -283,7 +283,7 @@ \section{Special divisors and the special splitting principle}\label{MSUDay}
 where the scheme ``\(\SDiv_0 \CP^\infty_E\)'' of \index{divisor!special}\textit{special divisors} is defined to parametrize those divisors which vanish under the summation map.  However, whereas the map \(BU(1)_E \to BU_E\) has an identifiable universal property---it presents \(BU_E\) as the universal formal group on the pointed curve \(BU(1)_E\)---the description of \(B\SU_E\) as a scheme of special divisors does not bear much immediate resemblance to a free object on the special divisor \((1 - [a])(1 - [b])\) classified by \[(\CP^\infty)^{\times 2}_E \xrightarrow{(1 - \L_1)(1 - \L_2)_E} B\SU_E \to BU_E = \Div_0 \CP^\infty_E.\]  Our task is thus exactly to justify this statement.
 
 \begin{definition}\label{DefinitionOfC2G}
-If it exists, let \(C_2 \G\) denote the symmetric square of \(\Div_0 \G\), thought of as a module over the ring scheme \(\Div \G\).  This scheme has the property that a formal group homomorphism \(\phi\co C_2 \G \to H\) is equivalent data to a symmetric function \(\psi\co \G \times \G \to H\) satisfying a rigidity condition (\(\psi(0, 0) = 0\)) and a \(2\)--cocycle condition as in \Cref{TwoCocycleConditionForBSUBundles}.
+If it exists, let \(C_2 \G\) denote the symmetric square of \(\Div_0 \G\), thought of as a module over the ring scheme \(\Div \G\).  This scheme has the property that a formal group homomorphism \(\phi\co C_2 \G \to H\) is equivalent data to a symmetric function \(\psi\co \G \times \G \to H\) satisfying a rigidity condition (\(\psi(a, 0) = 0\)) and a \(2\)--cocycle condition as in \Cref{TwoCocycleConditionForBSUBundles}.
 \end{definition}
 
 \begin{theorem}[{Ando--Hopkins--Strickland, unpublished}]\label{SDivModelsC2}