Аннотация:We observed the universal phenomenon of competition among multiple filaments generated during the propagation of intense femtosecond laser pulses in air. The backscattered fluorescence signal of nitrogen molecules excited inside multiple filaments yielded irregular changes from shot to shot without any correlation to the laser energy fluctuations. Numerical simulations reveal that the irregular fluorescence signal is due to a complex dynamics of interacting multi-filaments. In particular, we show that interference effects between two hot spots, that give rise two filaments, may either fuse together or further branch out creating new filaments. This process is determined by the separation of hot spots in the beam and thus is very sensitive to the initial laser pulse input conditions. Steep (sic).