Resonant photon-graviton conversion in EM fields: From earth to heaven

Gravitational radiation from high energy particles in modern accelerators is reviewed. We point out that the most effective way for laboratory production and detection of gravitons is through resonant photon-graviton conversion in a strong external EM field. Specific example using crystal channels for the γ → g → γ process is given, where the physical parameters needed for such a test appears to be reasonable. As another application of this effect in astrophysics, we show that the coupling between the cosmic microwave background radiation (CMBR) and the primordial magnetic field can induce a frequency-independent fluctuation in the photon flux. Using the observed CMBR fluctuation, we derive a bound on the primordial field strength. The effect can also convert the relic gravitons into photons. For the string cosmology it gives a new bound on the Hubble parameter at the Big Bang