{'fraction_non_alphanumeric': 0.02348993288590604, 'fraction_numerical': 0.003355704697986577, 'mean_word_length': 4.8881578947368425, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Superluminal wave front propagation at the shadow area behind an opaque disk

We demonstrated in theory and experiment superluminal properties of optical field propagation in the shadow area behind an opaque disk (Poisson's spot). The wave front of the field in the shadow zone is initially delayed with respect to unperturbed field. This phase shift gradually diminishes along the optical path, and therefore insures variation of the phase velocity of the field at the axis. This fact was verified experimentally by the method of interference with a tilted reference plane wave. A resulting excess of about c×10-5 was detected. Moreover, the result does not depend on the frequency of light oscillations. It means that a non-monochromatic field (e.g. short light pulse) will propagate without dispersion, what insures the equality of the group velocity to the phase velocity, both exceeding c.