These three appeared this year, present versions are dated April, October, and December 2003 http://arxiv.org/hep-th/0304027 [Broken] http://arxiv.org/hep-th/0304101 [Broken] http://arxiv.org/hep-th/0312140 [Broken] Jerzy K-G and co-authors discovered this year that in DSR (which he suggest should be called "quantum special relativity") the speed of any massless particle is c---independent of energy. The Lorentz algebra doesn't change although its action on momenta does. Both results appear in the first article linked: Daszkiewicz, Imilkowska, Kowalski "Velocity of particles in Doubly Special Relativity" The next article is longer and discusses the results at greater length: Kowalski-Glikman, Nowak "Doubly Special Relativity and de Sitter space" The third is authored solo: Kowalski-Glikman "Doubly Special Relativity and quantum gravity phenomenology". ------------------------------ It would be hard to overstate the unexpectedness and importance of these results, particularly the constancy of the speed of light. Until this year it was presumed that if, instead of only one observer-independent quantity, one postulates two (the low-energy speed of light and the Planck energy) then a photon's speed would vary with energy. Very high energy gamma photons were expected to travel perceptibly faster, so that a difference in time-of-flight would appear over very large distances. Kowalski-Glikman proves otherwise and points to a flaw in the earlier reasoning. These papers distinguish between DSR (or "DSR1") which K-G and his coworkers is developing and a later version ("DSR2") which Smolin and Magueijo investigated for the first time in 2002, in their paper "Generalized Lorentz invariance with an invariant energy scale" gr-qc/0207085. The presence of different versions complicates things but K-G manages to get all the versions into a single form. The energy-independent speed of light appears to be a robust result, valid for all versions. We seem to be looking at a Lorentz-invariant theory with two quantities (a speed and an energy) instead of one, which are the same for all observers. And where massless particles, such as photons, all travel at the same speed. To me this seems shocking and unintuitive. A lot has happened in quantum gravity in 2003. At the moment this K-G result seems the hardest to comprehend. It changes the expectations about what kind of information one may get from the forthcoming GLAST data.