Particle Creation in the Bell-Szekeres Spacetime

The quantization of a real massless scalar eld in a spacetime produced in a collision of two electromagnetic plane waves with constant wave fronts is considered. The background geometry in the interaction region, the Bell-Szekeres solution, is locally isometric to the conformally at Bertotti-Robinson universe lled with a uniform electric eld. It is shown that before the waves interact the Bogoliubov coe cients relating di erent observers are trivial and no vacuum polarization takes place. In the nonsingular interaction region neutral scalar particles are produced with number of created particles and spectrum typical of gravitational wave collision. PACS numbers: 04:62+ v; 04:20Jb; 04:30: w