%0 Journal Article %T An Elementary Differential Extension of Odd K-theory %A Thomas Tradler %A Scott O. Wilson %A Mahmoud Zeinalian %J Mathematics %D 2012 %I arXiv %X There is an equivalence relation on the set of smooth maps of a manifold into the stable unitary group, defined using a Chern-Simons type form, whose equivalence classes form an abelian group under ordinary block sum of matrices. This construction is functorial, and defines a differential extension of odd K-theory, fitting into natural commutative diagrams and exact sequences involving K-theory and differential forms. To prove this we obtain along the way several results concerning even and odd Chern and Chern-Simons forms. %U http://arxiv.org/abs/1211.4477v1