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

Testing fundamental principles with high-energy cosmic rays

It is not yet clear whether the observed flux suppression for ultra-high energy cosmic rays (UHECR) at energies above \simeq 4.10E19 eV is a signature of the Greisen-Zatsepin-Kuzmin (GZK) cutoff or corresponds, for instance, to the maximum energies available at the relevant sources. Both phenomena can be sensitive to violations of standard special relativity modifying cosmic-ray propagation or acceleration at very high energy, and would in principle allow to set bounds on Lorentz symmetry violation (LSV) parameters. But the precise phenomenological analysis of the experimental data is far from trivial, and other effects can be present. The effective parameters can be directly linked to Planck-scale physics or to physics beyond Planck scale. If a vacuum rest frame (VRF) exists, LSV can modify the internal structure of particles at very high energy. Conventional symmetries may also cease to be valid at energies close to the Planck scale. Other possible violations of fundamental principles and conventional basic hypotheses (quantum mechanics, quark confinement, energy and momentum conservation, vacuum homogeneity and "static" properties, effective space dimensions...) can also be considered and possibly tested in high-energy cosmic-ray experiments. Even below UHE (ultra-high energy), exotic signatures cannot be excluded. We present an updated discussion of the theoretical and phenomenological situation, including prospects for earth-based and space experiments and a simple potential interpretation of the observed UHECR composition in terms of LSV where the GZK cutoff would be replaced by spontaneous emission of photons or e+ e- pairs. As the OPERA result on a possible superluminal propagation of the muon neutrino was announced after the conference, we briefly comment on the consistency problems that a \simeq 2.5 x 10E-5 critical speed anomaly for the muon neutrino can raise.Comment: 4 pages, Proceedings of the XXIst International Europhysics Conference on High Energy Physics, Grenoble, France, July 2011. To be published by Proceedings of Science (already available

Lorentz violation, vacuum, cosmic rays, superbradyons and Pamir data

The possibility that Pamir data at very high energy cannot be fully explained by standard physics has recently led to the suggestion that the peculiar jet structure observed above ~ 10E16 eV could be due to a suppression of effective space transverse dimensions. The new pattern considered violates Lorentz symmetry. We point out that, in models with Lorentz symmetry violation, a suppression of available transverse energy for jets while conserving longitudinal momentum can be generated by new forms of energy losses at very high energy without altering space-time structure. An illustrative example can be superbradyon emission, where in all cases the superbradyon energy would be much larger than its momentum times c (speed of light). More generally, such phenomena could be due to the interaction of the high-energy cosmic ray with new vacuum and/or particle structure below the 10E-20 cm scale. Scenarios involving Lorentz symmetry violation but not superbradyons are also briefly considered.Comment: 7 pages, enlarged versio

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

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