Curvature Oscillations in Modified Gravity and High Energy Cosmic Rays
  It is shown that F(R)-modified gravitational theories lead to curvature oscillations in astrophysical systems with rising energy density. The frequency and the amplitude of such oscillations could be very high and would lead to noticeable production of energetic cosmic ray particles. 
E. V. Arbuzova, A. D. Dolgov, L. Reverberi
gr-qc astro-ph.CO hep-ph