Lorentz violation and ultrahigh-energy photons

Abstract

The propagation of photons, electrons and positrons at ultra-high energies above ∼ 10 19 eV can be changed considerably if the dispersion relations of these particles are modified by terms suppressed by powers of the Planck scale. We recently pointed out that the current non-observation of photons in the ultra-high energy cosmic ray flux at such energies can put strong constraints on such modified dispersion relations. In the present work we generalize these constraints to all three Lorentz invariance breaking parameters that can occur in the dispersion relations for photons, electrons and positrons at first and second order suppression with the Planck scale. We also show how the excluded regions in these three-dimensional parameter ranges would be extended if ultra-high energy photons were detected in the future.

Probing Lorentz Violating (Stringy) Quantum Space-Time Foam

“…Nevertheless, the phenomenology of such MDR, which I must stress once again is only one aspect of possible experimental signatures of quantum, gravity, is very rich, ranging at present from observations of the arrival times of photons from distant astrophysical sources, such as Active Galactic Nuclei (AGN) [13,14,15,16] and GammaRay-Bursts (GRB) [17], to synchrotron radiation spectral studies from distant nebulae [5], as well as studies focused on the absence of birefringence effects of astrophysical photons [18,19] and ultra-high-energy photons, with energies higher than 10 20 eV, and related phenomena [20]. To understand the basic idea behind these phenomenological studies, we mention that, for photons of different energies, emitted "simultaneously" (i.e.…”

Restrictions from Lorentz invariance violation on cosmic ray propagation

“…This mechanism converges to the introduction of an extra term in the dispersion relation of a single particle [10,[12][13][14][15][16][17][18][19][20]. Generically, this term can be motivated by the introduction of a not explicitly Lorentz invariant term at the free particle Lagrangian [21].…”

Lorentz invariance violation and chemical composition of ultra-high energy cosmic rays

“…Therefore, if a nucleus is observed with a certain energyĒ, the VC energy threshold must be larger thanĒ. Moreover, assuming that LIV is much smaller for photons than for nuclei [22,23,24], we consider only emission of soft photons. This is a valid assumption, as the phase space of the reaction just above threshold is large enough to warrant the short mean free path necessary to set constraints [20].…”

“…In particular, terms n = 2, coming from dimension five and six CPT even LIV operators, have been recently directly 1 constrained [20] in the hadronic sector by exploiting ultra high energy cosmic ray observations performed by the Pierre Auger Observatory (PAO) [21]. Indeed, the successful operation of the PAO has brought UHECRs to the interest of a wide community of scientists and already allowed to test fundamental physics (in particular Lorentz invariance in the QED sector) with unprecedented precision [22,23,24].…”