%0 Journal Article %T Inner products of 2-representations %A Nora Ganter %J Mathematics %D 2011 %I arXiv %X We define and calculate inner products of 2-representations. Along the way, we prove that the categorical trace Tr(-) of [Ganter and Kapranov, Representation and character theory in 2-categories, Sec. 3] is multiplicative with respect to various notions of categorical tensor product, and we identify the center of the category V^G of [loc. cit., Sec. 4.2]. We discuss applications, ranging from Schur's result about the number of projective representations to a formula for the Hochschild cohomology of a global quotient orbifold. %U http://arxiv.org/abs/1110.1711v2