The XXIst International Europhysics Conference on High Energy Physics (HEP 2011) was held in Grenoble, France, last July :

and my two original contributions can be found here (initial versions) :

(**1. COSMOLOGY**) http://indico.in2p3.fr/contributionDisplay.py?contribId=707&sessionId=13&confId=5116

Space and time are usually described by four real coordinates. But spin-1/2 particles cannot be described as representations of the standard rotation and Lorentz group. They correspond to the fundamental representations of their covering groups, SU(2) and SL(2,C). In my 1996-97 papers (arXiv:hep-ph/9610474, arXiv:physics/9702026 …), I suggested using instead a spinorial space-time. On then has two complex coordinates instead of the conventional four real ones.

With space-time SU(2) spinors, one can introduce a cosmic time *t* = | ξ | where | ξ | is the spinor modulus. *t *= 0 (ξ = 0) corresponds then to the origin of time in our Universe. This simple space-time geometry naturally leads to the relation between cosmic comoving speeds and distances usually called Hubble’s law but actually first formulated by Georges Lemaître. The law is automatically satisfied without any need to introduce standard matter, relativity, gravitation… The ratio between velocities and speeds turns out to be equal to the inverse of the age of the Universe, which is an excellent value on phenomenological grounds.

Dark energy seems to become unnecessary, and standard ΛCDM should be replaced by a more fundamental view of the origin of the Universe.

(**2. COSMIC RAYS AND RELATIVITY**) http://indico.in2p3.fr/contributionDisplay.py?contribId=678&sessionId=11&confId=5116

My contribution *Testing fundamental principles with high-energy cosmic rays*, posted also as arXiv:1202.1277 (Proceedings version), suggests a new interpretation of the observed composition of the UHECR (ultra-high energy cosmic-ray) spectrum. The fall of the spectrum woul not be generated by the conventional Greisen-Zatsepin-Kuzmin (GZK) mechanism, but by new physics involving a violation of standard special relativity for UHECR. The possible GZK suppression by Lorentz symmetry violation (LSV) in the presence of a privileged rest frame (the vacuum rest frame, VRF) was already considered in my April-May 1997 papers (arXiv:physics/9704017 , arXiv:physics/9705031). I now suggest that spontaneous decays at ultra-high energy (UHE) generated by the same kind of LSV can explain the UHECR composition seen by the AUGER experiment. Such decays turn out to occur at higher energies for heavier nuclei, as required by AUGER data.

The **Proceedings of HEP 2011** are available at the address : http://pos.sissa.it/cgi-bin/reader/conf.cgi?confid=134 , including my two contributions :

*Testing fundamental principles with high-energy cosmic rays*, PoS(EPS-HEP2011)390

http://pos.sissa.it/archive/conferences/134/390/EPS-HEP2011_390.pdf

*Pre-Big Bang, vacuum and noncyclic cosmologies*, PoS(EPS-HEP2011)479

http://pos.sissa.it/archive/conferences/134/479/EPS-HEP2011_479.pdf

with the Copyright : *“All contributions are published in PoS under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence. Every author submitting his/her contribution to PoS retains the copyright, and upon submission (s)he applies this license to his/her work*“.

Here attached are my two HEP 2011 papers (Proceedings versions) :

*Pre-Big Bang, vacuum and noncyclic cosmologies*

*Testing fundamental principles with high-energy cosmic rays*

with the same Copyright : Luis Gonzalez-Mestres (author),* Creative Commons Attribution-NonCommercial-ShareAlike Licence.*