Cosmic rays and tests of fundamental principles

Abstract

It is now widely acknowledged that cosmic rays experiments can test possible new physics directly generated at the Planck scale or at some other fundamental scale. By studying particle properties at energies far beyond the reach of any man-made accelerator, they can yield unique checks of basic principles. A well-known example is provided by possible tests of special relativity at the highest cosmic-ray energies. But other essential ingredients of standard theories can in principle be tested: quantum mechanics, uncertainty principle, energy and momentum conservation, effective space-time dimensions, hamiltonian and lagrangian formalisms, postulates of cosmology, vacuum dynamics and particle propagation, quark and gluon confinement, elementariness of particles... Standard particle physics or string-like patterns may have a composite origin able to manifest itself through specific cosmic-ray signatures. Ultra-high energy cosmic rays, but also cosmic rays at lower energies, are probes of both "conventional" and new Physics. Status, prospects, new ideas, and open questions in the field are discussed. The Post Scriptum shows that several basic features of modern cosmology naturally appear in a SU(2) spinorial description of space-time without any need for matter, relativity or standard gravitation. New possible effects related to the spinorial space-time structure can also be foreseen. Similarly, the existence of spin-1/2 particles can be naturally related to physics beyond Planck scale and to a possible pre-Big Bang era.

Pre-Big Bang, space-time structure, asymptotic Universe

“…The cosmic space at time t is described by the associated hypersphere with a natural positive space curvature and no critical speed at that stage. The law H = t −1 holds then automatically in the absence of matter and cosmological constant [9,15], just as in the previous negative curvature example. The associated Friedmann-like equation equivalent of (1) is then:…”

“…Suitable new cosmologies can be related to new ultimate constituents of matter such as superbradyons (superluminal preons [11]) beyond the original preon idea [12] and to new physics at ultra-high energy [13,14] possibly generated beyond Planck scale. Actually, it is even not obvious that the notion of Planck scale still makes sense or that quantum mechanics, relativity and grand unification of standard interactions are indeed relevant at these energy and distance scales [15,16]. The actual preon-like dynamics and the effective space-time geometry may obey substantially different physical principles [9,11].…”

“…In particular, the dark energy term in the standard Friedmann equations may be hiding a leading contribution of purely geometric origin unrelated to any cosmological constant or conventional quantum field [9,15]. The question of the role of cosmic space curvature is in this respect a major one, but measuring the actual curvature at large cosmological scales can be a very difficult task if the Universe is much larger than the observable one.…”

Value of H, space-time patterns, vacuum, matter, expansion of the Universe, alternative cosmologies

“…But as pointed out in previous papers [13,28], the situation can be radically different with a preonic vacuum structure naturally avoiding a permanent static presence of the (composite) QFT standard condensates and bosonic zero modes [29]. If the conventional particles are actually excitations of the physical vacuum, the underlying vacuum dynamics can generate them in specific situations and in a way compatible with the successful experimental tests of QFT.…”

“…Its properties have been briefly reminded in [15,39] and previously dealt with in several papers including [13,28], [40,41] and [14,42].…”