4 papers
A non-semisimple Kitaev lattice model
Sebastian Halbig, Ulrich Krähmer
The construction of the topologically protected code space of Kitaev's model for fault-tolerant quantum computation is extended from complex semisimple to arbitrary finite-dimensio…
Duplicial functors, descent categories and generalized Hopf modules
Ivan BartuloviÄ, John Boiquaye, Ulrich Krähmer
Böhm and Åtefan have expressed cyclic homology as an invariant that assigns homology groups to right and left coalgebras resp…
The ring of differential operators on a monomial curve is a Hopf algebroid
Ulrich Krähmer, Myriam Mahaman
This article considers cuspidal curves whose coordinate rings are numerical semigroup algebras. Using a general result about descent of Hopf algebroid structures, their rings of di…
Clones from comonoids
Ulrich Krähmer, Myriam Mahaman
The fact that the cocommutative comonoids in a symmetric monoidal category form the best possible approximation by a cartesian category is revisited when the original category is o…