4,974 research outputs found
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
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