### Recent Submissions

• #### [2015-02-12]K-Theory and Pseudospectra for Topological Insulators [dataset] ﻿

We derive formulas and algorithms for Kitaev's invariants in the periodic table for topological insulators and superconductors for finite disordered systems on lattices with boundaries. We find that $K$-theory arises ...
• #### [2014-01-09]Quantitative K-theory and spin Chern numbers [dataset] ﻿

We examine the various indices defined on pairs of almost commuting unitary matrices that can detect pairs that are far from commuting pairs. We do this is two symmetry classes, that of general unitary matrices and ...
• #### [2013-12-17]Principal angles and approximation for quaternionic projections [dataset] ﻿

We extend Jordan's notion of principal angles to work for two subspaces of quaternionic space, and so have a method to analyze two orthogonal projections in the matrices over the real, complex or quaternionic field (or ...
• #### [2013-12-02]Estimating norms of commutators [dataset] ﻿

\begin{abstract} We find estimates on the norm of a commutator of the form $[f(x),y]$ in terms of the norm of $[x,y]$, assuming that $x$ and $y$ are bounded linear operators on Hilbert space, with $x$ normal and with ...
• #### [2013-11-25]Computing a logarithm of a unitary matrix with general spectrum [dataset] ﻿

\begin{abstract} We analyze an algorithm for computing a skew-Hermitian logarithm of a unitary matrix, and also skew-Hermitian approximate logarithms for nearly unitary matrices. This algorithm is very easy to implement ...

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