AUGER-HiRes results and models of Lorentz symmetry violation

The implications of AUGER and HiRes results for patterns of Lorentz symmetry violation (LSV) are examined, focusing on weak doubly special relativity (WDSR). If the Greisen-Zatsepin-Kuzmin (GZK) cutoff is definitely confirmed, the mass composition of the highest-energy cosmic-ray spectrum will be a crucial issue to draw precise theoretical consequences from the experimental results. Assuming that the observed flux suppression is due to the GZK mechanism, data will allow in principle to exclude a significant range of LSV models and parameters, but other important possibilities are expected to remain open : Lorentz breaking can be weaker or occur at a scale higher than the Planck scale, unconventional LSV effects can fake the GZK cutoff, threshold phenomena can delay its appearance... Space experiments appear to be needed to further test special relativity. We also examine the consequences of AUGER and HiRes data for superbradyons. If such superluminal ultimate constituents of matter exist in our Universe, they may provide new forms of dark matter and dark energy.Comment: Talk given at the CRIS (Cosmic Ray International Seminar), La Malfa, September 15-19, 2008. To be published in the Proceeding

CMB B-modes, spinorial space-time and Pre-Big Bang (II)

The BICEP2 collaboration reported recently a B-mode polarization of the cosmic microwave background (CMB) radiation inconsistent with the null hypothesis at a significance of > 5 {\sigma}. This result has been often interpreted as a signature of primordial gravitational waves from cosmic inflation, even if actually polarized dust emission may be at the origin of such a signal. Even assuming that part of this CMB B-mode polarization really corresponds to the early Universe dynamics, its interpretation in terms of inflation and primordial gravitational waves is not the only possible one. Alternative cosmologies such as pre-Big Bang patterns and the spinorial space-time (SST) we introduced in 1996-97 can naturally account for such CMB B-modes. In particular, the SST automatically generates a privileged space direction (PSD) whose existence may have been confirmed by Planck data. If such a PSD exists, it seems normal to infer that vector perturbations have been present in the early Universe leading to CMB B-modes in suitable cosmological patterns. Inflation would not be required to explain the BICEP2 result assuming it really contains a primordial signal. More generally, pre-Big Bang cosmologies can also generate gravitational waves in the early Universe without any need for cosmic inflation. We further discuss here possible alternatives to the inflationary interpretation of a primordial B-mode polarization of cosmic microwave background radiation.Comment: 11 page

Lorentz Symmetry Violation and High-Energy Cosmic Rays

We discuss possible violations of Poincare's relativity principle at energy scales close to Planck scale and point out the potentialities of high-energy cosmic-ray physics to uncover these new phenomena.Comment: Talk given at the Workshop on "Topics in Astroparticle and Underground Physics", Gran Sasso September 1997. 3 pages, LaTex, uses espcrc2.st

Physics Opportunities Above the Greisen-Zatsepin-Kuzmin Cutoff: Lorentz Symmetry Violation at the Planck Scale

Special relativity has been tested at low energy with great accuracy, but these results cannot be extrapolated to very high-energy phenomena: this new domain of physics may actually provide the key to the, yet unsettled, question of the ether and the absolute rest frame. Introducing a critical distance scale, a, below 10E-25 cm (the wavelength scale of the highest-energy observed cosmic rays) allows to consider models, compatible with standard tests of special relativity, where a small violation of Lorentz symmetry (a can, for instance, be the Planck length) leads to a deformed relativistic kinematics (DRK) producing dramatic effects on the properties of very high-energy cosmic rays. For instance, the Greisen-Zatsepin-Kuzmin (GZK) cutoff does no longer apply and particles which are unstable at low energy (neutron, some hadronic resonances like the Delta++, possibly several nuclei...) become stable at very high energy. In these models, an absolute local rest frame exists (the vacuum rest frame, VRF) and special relativity is a low-momentum limit. We discuss the possible effects of Lorentz symmetry violation (LSV) on kinematics and dynamics, as well as the cosmic-ray energy range (well below the energy scale associated to the fundamental length) and experiments (on earth and from space) where they could be detected.Comment: 11 pages, LaTeX, requires aipproc.sty; invited talk at the Workshop on "Observing Giant Cosmic Ray Air Showers for > 10E20 eV Particles from Space", Univ. of Maryland, Nov 13-15, 199