de Sitter Relativity: a New Road to Quantum Gravity--Aldrovandi and Pereira take risk Aldrovandi and Pereira are at the ITP at Sao Paolo State University. They have taken a risky step and proposed to modify General Relativity so that it should be locally de Sitter instead of locally Lorentzian (or Poincaresque). What they get are two results that look too good to be true (and I am sure they know this, they are not novices.) They get a reasonable value of the cosmo constant. And what is even more risky: they retrodict the high energy GAMMARAY DELAY INITIALLY FOUND BY the new Canary Island Cherenkov telescope called "MAGIC". MAGIC is a good consortium of excellent German Italian Spanish etc astrophysicists and they have an excellent instrument, currently the largest optical dish in the world. they are 130 people and they have published and delivered many respectable papers. But in August this year, they claimed to have observed a 4 minute delay in some 2 TeV photons coming from Makarian 501. This could very easily be a WRONG OBSERVATION and their announcement was strongly condemned by vocal physics bloggers. The commentators disapproved of MAGIC for publishing on the basis of just one observed flare event and also for taking Ellis and Mavromatos on board, who mentioned there might be some QUANTUM GRAVITY EXPLANATION. The commentators opined that Ellis and Mavromatos were premature and that the consortium should have waited and observed more flares. Above all they should not have mentioned a possible QG implication.* Now Aldrovandi and Pereira have gone and calculated that there SHOULD HAVE BEEN THIS DELAY because of the deSitterness of spacetime. This could bring disapproval down on their heads and even ridicule. What if MAGIC repeats the observation with another flare, and doesn't find the delay the next time???!!! then A & P will look foolish. And they surely know this because they are IMHO the two top theoretical physics/cosmology people in Brazil. I have been watching their papers and I think they are tops and they are obviously seasoned mature research people, not newcomers. So this was a deliberate calculated step to take. Evidently they really believe that you should modify Gen Rel to be deSitter and that this will give you numbers for the cosmological constant (which nobody else can explain) and for the MAGIC 4 minute delay (which almost nobody else seems to believe.) I have to respect this. All we can do is watch and see what happens to this idea. http://arxiv.org/abs/0711.2274 de Sitter Relativity: a New Road to Quantum Gravity R. Aldrovandi, J. G. Pereira 17 pages (Submitted on 14 Nov 2007) "The Poincare' group generalizes the Galilei group for high-velocity kinematics. The de Sitter group is here assumed to go one step further, generalizing Poincare' as the group governing high-energy kinematics. Algebraically, this is done by supplementing spacetime translations with proper conformal transformations. This change in special relativity implies concomitant changes in general relativity -- yielding a de Sitter general relativity. The source current turns out to include now, in addition to energy-momentum, the proper conformal current, which appears as the origin of the cosmological constant. In consequence, it is no longer a free parameter, and can be determined in terms of other quantities. When applied to the propagation of ultra-high energy photons, de Sitter general relativity gives a good estimate of the time delay observed in extragalactic gamma-ray flares. It can, for this reason, be considered a new approach to quantum gravity." *I didn't agree with all the scolding that went on in the blogs. I was glad MAGIC published the paper, which contained interesting information.