The excitation spectrum of rotating strings with masses at the ends

We compute the spectrum of excitations of the rotating Nambu-Goto string with masses at the ends. We find interesting quasi-massless modes in the limit of slow rotation and comment on the nontrivial relation between world-sheet and target space energy.Comment: 13 pages, 1 figure, v2: Typos corrected, v3: fina

Divergences in QFT on the Noncommutative Minkowski Space with Grosse-Wulkenhaar potential

We study quantum field theory on the two-dimensional Noncommutative Minkoswki space with a Grosse-Wulkenhaar potential. We explicitly construct the retarded propagator and show that it is not a tempered distribution. This leads to problems when trying to define planar products of such distributions, as they appear in the Yang-Feldman series. At and above the self-dual point, these can no longer be defined, not even at different points. This shows that we do not deal with an ordinary ultraviolet divergence.Comment: 8 pages, Contribution to the proceedings of the Corfu Summer Institute on Elementary Particles and Physics 201

Locally covariant chiral fermions and anomalies

We define chiral fermions in the presence of non-trivial gravitational and gauge background fields in the framework of locally covariant field theory. This allows to straightforwardly compute the chiral anomalies on non-compact Lorentzian space-times, without recourse to a weak field approximation.Comment: 19 page

Dispersion relations in the noncommutative \phi^3 and Wess-Zumino model in the Yang-Feldman formalism

We study dispersion relations in the noncommutative \phi^3 and Wess-Zumino model in the Yang-Feldman formalism at one-loop order. Nonplanar graphs lead to a distortion of the dispersion relation. We find that the strength of this effect is moderate if the scale of noncommutativity is identified with the Planck scale and parameters typical for a Higgs field are employed. The contribution of the nonplanar graphs is calculated rigorously using the framework of oscillatory integrals.Comment: 23 pages, 2 figures. v2: Minor corrections and changes in the presentatio