“…This form of the reality condition is used byCabella and Kamionkowski (2005),Challinor (2004Challinor ( , 2009, Challinor and Peiris (2009), Durrer (2008), Kamionkowski et al (1997), Lin and Wandelt (2006), among others. Introduce the following notation: m + = max{m, 0} = (|m| + m)/2, m − = max{−m, 0} = (|m| − m)/2.…”