Higher-Dimensional Algebra II: 2-Hilbert Spaces

A 2-Hilbert space is a category with structures and properties analogous to those of a Hilbert space. More precisely, we define a 2-Hilbert space to be an abelian category enriched over Hilb with a *-structure, conjugate-linear on the hom-sets, satisfying = = . We also define monoidal, braided monoidal, and symmetric monoidal versions of 2-Hilbert spaces, which we call 2-H*-algebras, braided 2-H*-algebras, and symmetric 2-H*-algebras, and we describe the relation between these and tangles in 2, 3, and 4 dimensions, respectively. We prove a generalized Doplicher-Roberts theorem stating that every symmetric 2-H*-algebra is equivalent to the category Rep(G) of continuous unitary finite-dimensional representations of some compact supergroupoid G. The equivalence is given by a categorified version of the Gelfand transform; we also construct a categorified version of the Fourier transform when G is a compact abelian group. Finally, we characterize Rep(G) by its universal properties when G is a compact classical group. For example, Rep(U(n)) is the free connected symmetric 2-H*-algebra on one even object of dimension n.Comment: 63 pages, LaTeX, 11 figures in encapsulated Postscript, 2 stylefile

Diagonal And Triangular Matrices

HAMDAN ALSULAIMANI, for the Master of Science in Mathematics, presented on NOV 6 2012, at Southern Illinois University Carbondale. TITLE: Diagonal (Triangular) Matrices PROFESSOR: Dr. R. Fitzgerald I present the Triangularization Lemma which says that let P be a set of properties, each of which is inherited by quotients. If every collection of transformations on a space of dimension greater than 1 that satisfies P is reducible, then every collection of transforma- tions satisfying P is triangularizable. I also present Burnside’s Theorem which says that the only irreducible algebra of linear transformations on the finite-dimensional vector space V of dimension greater than 1 is the algebra of all linear transformations mapping V into V. Moreover, I introduce McCoy’s Theorem which says that the pair {A,B} is triangularizable if and only if p(A,B)(AB-BA) is nilpotent for every noncommutative polynomial p. And then I show the relation between McCoy’s Theorem and Lie algebras