Latest results on gamma-ray pulsars with Fermi

The Fermi Large Area Telescope (LAT) has been scanning the gamma-ray sky since 2008. The number of pulsars detected by the LAT now exceeds 200, making them by far the largest class of Galactic gamma-ray emitters. I discuss some of the latest pulsar discoveries made by the LAT, in particular those made since the release of the Pass 8 data.Comment: 5 pages, to appear in Il Nuovo Cimento

Fermi-LAT searches for gamma-ray pulsars

The Large Area Telescope (LAT) on the Fermi satellite is the first gamma-ray instrument to discover pulsars directly via their gamma-ray emission. Roughly one third of the 117 gamma-ray pulsars detected by the LAT in its first three years were discovered in blind searches of gamma-ray data and most of these are undetectable with current radio telescopes. I review some of the key LAT results and highlight the specific challenges faced in gamma-ray (compared to radio) searches, most of which stem from the long, sparse data sets and the broad, energy-dependent point-spread function (PSF) of the LAT. I discuss some ongoing LAT searches for gamma-ray millisecond pulsars (MSPs) and gamma-ray pulsars around the Galactic Center. Finally, I outline the prospects for future gamma-ray pulsar discoveries as the LAT enters its extended mission phase, including advantages of a possible modification of the LAT observing profile.Comment: Proceedings of the IAU Symposium 291, IAU XXVIII General Assembly, Beijing, China, August 2012: "Neutron Stars and Pulsars: Challenges and Opportunities after 80 years", Editor: Joeri van Leeuwen. To be published by Cambridge University Press. 6 page

VB-groupoids and representation theory of Lie groupoids

A VB-groupoid is a Lie groupoid equipped with a compatible linear structure. In this paper, we describe a correspondence, up to isomorphism, between VB-groupoids and 2-term representations up to homotopy of Lie groupoids. Under this correspondence, the tangent bundle of a Lie groupoid G corresponds to the "adjoint representation" of G. The value of this point of view is that the tangent bundle is canonical, whereas the adjoint representation is not. We define a cochain complex that is canonically associated to any VB-groupoid. The cohomology of this complex is isomorphic to the groupoid cohomology with values in the corresponding representations up to homotopy. When applied to the tangent bundle of a Lie groupoid, this construction produces a canonical complex that computes the cohomology with values in the adjoint representation. Finally, we give a classification of regular 2-term representations up to homotopy. By considering the adjoint representation, we find a new cohomological invariant associated to regular Lie groupoids.Comment: v5: Introduction is completely rewritten, many other improvements in the exposition. v6: Implements numerous corrections and changes suggested by referees, most notably a significant simplification of the calculations in Appendix A.2. Final version, to appear in J. Symp. Geo