Gravitational wave analog to the parametric acoustic array

Abstract

The gravitational intensity radiated by a 100% modulated well-collimated and truncated laser beam has been shown by me [JETP Letters 4, 225 (1966)] to be S = (kc−5)PE2(4πR02)−1 {1 − cos[kmL (1 − cosφ)]}[(1 − cosφ)−2sin4φ]n. The crucial nature of this expression is the fact that S vanishes in the forward direction as a consequence of the sin4φ term characteristic of tensor waves. For vector waves and for scalar waves the sin4φ term is replaced by sin2φ and by 1, respectively, and then resonant interaction leads to a Rutherford-like peaking in the forward direction which corresponds, in the scalar case, to the parmetric acoustic array. It is clear that gravitational radiation from ultrarelativistic particles will not exhibit the forward peaking characteristic of electromagnetic radiation from ultrarelativistic charged particles which corresponds to the vector case. [This work was supported by the U. S. Navy Office of Naval Research.]