Collective Relativistic Phenomena with Femtosecond Laser Pulses

Relativistically invariant self-similarity approach is applied for description of collective particle production by femtosecond laser pulses. Recent outstanding advances in laser technique, namely, generation of ultrashort laser pulses ensuring intensities on the target of an order of 10 W/cm opened a wide class of new phenomena of production of intense and "highly-coherent" beams of radiations, including photons and charged particles (e.g., [1]). Theoretically, the regime of "coherent" particle generation was first predicted in [2] and then confirmed numerically [3]. It is sometimes referred to as "bubble regime". Generation of positron beams by femtosecond laser pulses has also been reported [4]. A comprehensive description of particular experimental results is complicated. This motivates a desire of application of the self-similarity approach in order to reduce the number of variables considered [7].