Violation of Lorentz invariance and neutral component of UHECR

The observed clustering of ultra-high energy cosmic rays suggests the existence of a neutral component. The models with violation of Lorentz invariance may explain this component by neutrons becoming stable above some threshold energy E-0. The protons, in turn, may become unstable above some energy E-1 > E-0. We calculate the dependence of the threshold energies Eo and E, on the parameters of the model and find E-1/E-0 greater than or equal to 1.5. We argue that the characteristic threshold behavior of charged and neutral components may be used as the specific signature of models with violation of Lorentz invariance. The existence of the neutron stability threshold Eo can be investigated with already existing data. (C) 2002 Elsevier Science B.V. All rights reserved.